TABLE OF CONTENTS CHAPTER PAGE 1. Photosynthesis 1 2. Transport in plants eee Tee |3. Human digestivesystem SS 28 /4Human circulatory sys SS ; 44 Respiratory system 59 6, Locomotion 70 7. Reproduction 85 8. Immunity 101 9. Human Diseases ; 106 10. Human Population EEE HEEEE EEE met 11, Tropisms: 118 12. Excretion and Osmo-regulation _ wi 13. Genetics 127 14, Evolution 139 15. Living Things and Environment 144 16. Coordination 17, Cancer viCHAPTER 1 PHOTOSYNTHESIS (PLANT NUTRITION) By the end of this topic, students should be able to: 1. Label diagram of a cross section of a leaf as seen through a light microscope. State the functions of the parts of a leaf. Explain the adaptation of leaves for photosynthesis. Label a mesophyll cell as seen through an electron microscope. Explain the function of parts of a plant cell. Describe the process of photosynthesis. State functions of mineral elements in photosynthesis. Carry out investigations on types of pigments in leaves. ). Explain what happens to glucose after photosynthesis. 10. Explain importance of photosynthesis, 11.Carry out experiments in photosynthesis. SRN SARL Nutrition is the process of acquiring energy and materials needed to maintain life. Energy is defined as the capacity to do work. Energy is neither created nor destroyed (the of conservation of energy). However, energy can be changed from one form to anothe ‘occurs in various forms for example light and heat. Some organisms like plants obtain energy by converting some forms of energy using inorg substances, for example, carbon dioxide. These are described as autotrophs. On the c hand, heterotrophs depend on this already made food energy. een “fieterotrop Figure 1, Examples of an autotroph and heterotroph Despite energy taking several forms, only light and chemical are suitable energy source living things. Organisms that uso light as a source of energy are described photoautotrophic or photosynthetic whilst those using chemicals are describe¢ chemosynthetic or chemoautotrophic.The process whereby plants make their own food energy from inorganic substances using lig is called photosynthesis. It takes place in green parts of plants mainly leaves. PARTS OF A LEAF mid i transverse section Figure 2. External parts of a leaf A leaf consists of a flat, thin and broad blade (lamina) attached to the stem of a plant by a Ie stalk. By holding this leaf away from the stem, the stalk (petiole) exposes it for maximu light. Inside the leaf stalk there is the vascular bundle consisting of xylem and phloem. The xyle brings water and mineral salts to the leaf and the phloem takes away organic substance (food) to other parts of a plant after being produced. Even though the leaf is so thin; it has several layers of cells inside with different functions. aylemvessel~ phloem ea er epidermis Figure 8. Internal parts of a leaf as seen through a light microscope (transverse section) From the diagram above, it is seen that there are two layers, 1. Epidermal layers2. Mesophyll layers (meso means middle, phyil means leaf) Upper and lower epidermis ‘They consist of one layer of thin, flattened cells lacking chloroplasts. External walls are covered with cuticle, a waxy substance produced by the epidermal cells. Upper and lower epidermises contain microscopic pores called stomata surrounded by pairs guard cells. Below is a diagram of stomata. Figure 4. The stomata Functions of upper and lower epidermis 1. They offer protection to inner parts from damage. 2. Cuticle prevents or protects a leaf from drying and infection. 3, Stomata are sites of gaseous exchange. 4. Allows light to penetrate since they have no chlorophyll. Palisade mesophyll It consists of tall, column shaped cells. Palisade mesophyll cells contain numerous chloroplasts. ‘The cells are tightly packed with no air space. Chloroplasts may move towards light. Functions of the palisade mesophyll 1. This is the main site for photosynthesis in leaves. Spongy mesophyll It consists of irregular shaped cells that fit loosely to give large air spaces. Spongy mesophyll cells contain less chloroplast as compared to palisade cells. Functions of the spongy mesophyll 1. It is site of photosynthesis but has fewer chloroplasts than palisade cells. 2. It is site for gaseous exchange. 3, The cells store starch produced by photosynthesis. Vascular tissues ‘These are extensive finely branching network tubes through the leaf. ‘There are two types; xylem and phloem tissues. Functions of the vascular tissues 1. The xylem conducts water and mineral salts from the soil to the leaves. 32. The phloem removes products of photosynthesis to other parts of a plant. 3. They provide support to the leaf blade. EXERCISE 1.1 1. Explain the role of the following in photosynthesis: a. Xylem b. Spongy mesophyll ¢. Epidermal layers 2. Describe three features of the leaf which help to provide an efficient supply of car dioxide to the chloroplasts in the mesophyll cells? ADAPTATIONS OF LEAVES FOR PHOTOSYNTHESIS 1. Presence of stomata — for gaseous exchange. 2. Presence of guard cells — control the opening of stomata so that carbon dioxide and oxygen get into and out the leaf. 3. Presence of chloroplasts ~ contain chlorophyll for photosynthesis. 4. Large air space- for gaseous diffusion. 5. Presence of vascular tissues — a. Xylems supply water and mineral salts to the leaves. b. Both xylem and phloem support the leaf for maximum exposure. c. Phloems remove products of photosynthesis to other parts of a plant. 6. Presence of cuticle — prevents drying and infections of the leaves. ADAPTATIONS OF PALISADE MESOPHYLL FOR CAPTURING MORE LIGHT 1. Contain a lot of chloroplasts. 2, Cells have a column shape or are cylindrical hence more cells can be closely pack together. 3. It is located on top of the leaf. 4, Chloroplasts can move towards light. EXERCISE 1.2 Figure below show: follow. section through a green leaf. Study it to answer the questions that 1. With reference to the parts W - Z, explain how a leaf is involved in the manufacturing of carbohydrates. ‘a. State any three adaptations of the palisade mesophyll for photosynthesis b, Explain any five adaptations of leaves for photosynthesis? c. Name the labeled parts above.Parts of a mesophyll cell Acell is the basic structural and functional unit of living things. It was first discovered by Robert Hooke in 1665. Acell has three parts with many structures in those parts. PARTS OF A CELL mitochondrion _— — ‘ytoplasem —— Figure 6. A plant spongy mesophyll cell A cell has the following parts: a) Cell surface. b) Cytoplasm. c) Nucleus. a) Cell surface of plant cell consists of; Cell wall. Cell membrane.©) Cytoplasm of plant cells contains the following structures; Mitochondria, Chloroplasts. iii, Vacuole. iv. Endoplasmic reticulum v. Ribosome. vii Golgi complex. c) The nucleus consists of a nuclear membrane and chromosomes. Cell wall It is the outer most layer of plant cell. It consists of cellulose and other complex polysaccharides. Functions of the cell wall 1. It provides physical support and protection. 2. It prevents bursting of plant cells due to osmosis 3, It is one of the pathways of water and mineral salts. Cell membrane It consists of two layers, protein and lipid layer. It is celectively permeable. Functions of the cell membrane 1. It controls movement of substance into and out of the cells. Mitochondria Tt is sausage shaped. It is surrounded by two membranes. Inner membrane is highly folded. This increases the surface area to allow more reactions in it. It has its own deoxyribonucleic acid (DNA). Figure 7. The mitochondrion Functions of mitochondria 1, It is a site for aerobic respiration hence a place where energy is produced. Chloroplasts ‘They are ovoid in shape. They have two membranes but the inner membrane is not folded like the mitochondria. They contain chlorophyll. Below is a structure of a chloroplast.Figure 8. A chloroplast Functions of chloroplasts 1. It is a place where photosynthesis takes place. Vacuole It is sac surrounded by a single membrane called tonoplast. It contains cell sap (a concentrated solution of various substances, for example, salts, sugar and enzymes. Functions of the vacuole 1. It is used as a storage place of substances for example waste products and starch. 2. It is responsible for movement of water in and out of cells. Endoplasmic reticulum It is a system of flattened membrane- bound sacs. There are two types: a) Rough endoplasmic reticulum. It is studded with ribosomes. 6) Smooth endoplasmic reticulum. It does not have ribosomes. Functions of the endoplasmic reticulum a) Rough endoplasmic reticulum It transports proteins made by ribosomes. b) Smooth endoplasmic reticulum It is a site of lipid and steroid synthesis. Ribosomes These are places where proteins are produced. Golgi complex It is a stack of flattened membrane-bound sacs. It buds off from endoplasmic reticulum. Functions of Golgi complex 1. It is responsible for internal processing and transport system within or outside th cell. EXERCISE 1.3 a. Below is a diagram showing a structure from the cytoplasm of a plant cell.i, Define an Organelle? ii, Identify the structure above? iii, Name the process that takes place in the structure above? iv. The structure above has a double membrane. Of what importance is the inn membrane of the above structure highly folded? b. Make a comparison table to summarize the simila and animal cells. ¢. How can a plant be affected if the palisade cells of its leaves lacked the following: i, Mitochondria Chloroplasts Ribosome iv. Smooth endoplasmic reticulum PHOTOSYNTHESIS AS A PROCESS Photosynthesis is a process whereby plant cells through chloroplasts combine water and carbon dioxide to produce glucose as a main product and oxygen as a by ~product. ‘The energy comes from the sun and it is trapped by chlorophyll and converted to chemical energy. WORD EQUATION FOR PHOTOSYNTHESIS Water tcarbon dioxide <—=—==—=r> glucose + oxygen jes and differences between pla CHEMICAL EQUATION FOR PHOTOSYNTHESIS (balanced) GHz 0+6CO2 ‘CoH 1206 +602 However, the equations above do not tell us what actually happens; they are only telling us about what the raw materials are and what the products. Photosynthesis takes place in two stages, Light dependent Stage and Light independent Stage. A. Light dependent stage It is the first stage of photosynthesis and depends on light. Light energy from the sun is absorbed by the chlorophyll and converted to chemical energy. (ATP), this process is called photophosphorylation. Again, light energy split water molecules into hydrogen and oxygen atoms, a process called photolysis. Oxygen atoms combine chemically to form oxygen molecules which are used in respiration an excess oxygen molecules diffuse outside the leaf through stomata. Hydrogen molecules become the law materials for the second stage. B. Light independent stage It is the second stage of photosynthesis. Tt does not depend on light.In this stage, hydrogen atoms react with carbon dioxide to produce glucose - a process called reduction. Excess glucose molecules combine chemically with each other to produce starch, a process called condensation. WHAT HAPPENS TO GLUCOSE AFTER PHOTOSYNTHESIS . Itis used in respiration to produce energy. It is converted to starch and stored for future use. . It is used in the formation of cellulose (polysaccharides). . It is converted to lipids especially oils and stored for example in groundnuts. It reacts with nitrogen, phosphorus or sulfur to produce proteins. EXERCISE 1.4 a) Name the four chemical reactions involved in the process of photosynthesis? b) Name two raw materials of the second stage of photosynthesis? ©) Write an essay describing the fate of glucose after being produced? sae PRACTICAL ACTIVITY STARCH TEST One of the fates of glucose soon after photosynthesis is its conversion to starch and store for future use. It is therefore against this background whereby the presence of starch cz erve as evidence for photosynthesis. water ethanol cold water iodine Figure 9. A process of testing a leaf for starch PROCEDURE 1. Pluck a leaf from a plant and dip it in boiling water-this kills the leaf by stopping all b chemical reactions. This also makes the leaf permeable to reagents for example iodine. 2, The leaf is taken from boiled water and put in a test tube containing ethanol and the te tube is dipped in a beaker of boiled water -no direct heating of alcohol since it flammable -this removes chlorophyll. 8. The leaf is then washed in cold water ~to remove ethanol and soften it. 4, The leaf is then spread on a white tile and few drops of iodine are dropped on it - to s¢ colour changes. RESULTS 1. Blue/black color indicates presence of starch 2. Brown color, the colour of iodine, indicates absence of starch.EXERCISE 1.5 1. Name the four chemical reactions that take place in the process of photosynthesis? 2, State two products and raw materials in the second stage of photosynthesis? 8. Write an essay describing what happens to glucose after being produced in leaves? 4. During the process of testing a leaf for starch, what is the reason for dipping the le: in boiling water? INTERDEPENDENCE OF PHOTOSYNTHESIS AND RESPIRATION Photosynthesis uses carbon dioxide and water as raw materials and produces glucose as the main product and oxygen as a by-product. On the other hand, respiration uses glucose and oxygen as raw materials and releases carbon dioxide, water and energy. ‘This means that during the day, the only time when photosynthesis takes place naturally, these processes can depend on each other because the products of photosynthesis can become the raw materials for respiration and the products of respiration can become the raw material for photosynthesis. Usually, during the day, the process of photosynthesis is faster than respiration. Therefore, a. A lot of oxygen is produced than it is used by respiration hence a leaf releases oxygen to the atmosphere. b. More glucose is produced by photosynthesis than it is being used by respiration hence some glucose is converted to starch and stored. ¢. Less carbon dioxide is produced by respiration than used by photosynthesis hence carbon dioxide enters the leaf by diffusion from the atmosphere. carbon dioxide oxygen Figure 10. Gas exchange in a leaf during the day During the night there is no photosynthesis taking place naturally hence respiration is the only process taking place. Therefore during the night; a, More carbon dioxide is produced by the leaf through respiration hence a leaf releases carbon dioxide to the atmosphere. b. More oxygen is required by the leaf cells to respire hence oxygen enters the leaf from the atmosphere where it is in abundance. 10Oxygen Figure 11. Gas exchange in a leaf during the night During low light intensities, for example at dawn and dusk, the rate of photosynthesis m equal the rate of respiration as the amount of glucose and oxygen produced by photosynther is just enough to be used by respiration, as such, there would be no gas exchange between t atmosphere and the leaf. This condition is called compensation point. MINERAL ELEMENTS AND PHOTOSYNTHESIS A mineral element in chemistry is any naturally occurring chemical element or compound. Mineral elements have a number of functions to plants particularly in photosynthesis. Examples of mineral elements necessary for photosynthesis are nitrogen, phosphorus, sulfur, magnesium, potassium, carbon, hydrogen, oxygen and iron. Mineral elements have the following functions: Formation of chlorophyill for example magnesium and iron. Opening and closing of stomata for example potassium. Formation of energy carrier molecules for example phosphorus. Protein formation for example nitrogen, sulfur, phosphorus. Formation of glucose carbon, hydrogen and oxygen. Sa ee PHOTOSYNTHETIC PIGMENTS A pigment, in biology, is any chemical molecule that reflects or transmits visible light, or bot! ‘The colour of a pigment depends on its selective absorption of certain wavelengths of light an its reflection of others. For example, chlorophyll, one of plant pigments, absorbs violet-blue and orange-red light, converting this light energy to chemical energy, and reflects green light This is the reason why, chlorophyll appears green. ‘The role of the pigments is to absorb light energy and convert it to chemical energy th powers the process of photosynthesis. ‘These pigments fall into two classes. a) Chlorophyll. b) Carotenoides. a) Chlorophyll ‘These are the main photosynthetic pigments. Chlorophylis are the only pigments that are capable of converting light energy in chemical energy. ab) Carotenoids These are accessory pigments of the plant. Fall into three classes. i. Xanthophyils (yellow) ii, Carotenes (orange) iii, Phycocyannins (blue or purple) Carotenoides absorb light energy and transfer it to chlorophyll which converts it to chemi: energy. ee 16 |. Two potted plants are left in two different rooms, A and B. Room A has green li ‘emitting green rays and room B has red lights emitting red rays, If after 12 hours lei from both plants are plucked and tested for photosynthesis, which leaves would con starch. Explain your answer? 2. Design an experiment in an essay form to show that in a leaf there are more pigm« ether than chlorophyll. In your answer include material, procedure and exper results, (Hint-chromatography and pigment extraction) 3, Under what circumstance do leaves take in oxygen and give out carbon dioxide? 4. How do plants make proteins? IMPORTANCE OF PHOTOSYNTHESIS 1. It makes energy and carbon available to living things in form of food. It produces oxygen for respiration. It reduces carbon dioxide in the atmosphere hence prevents global warming. Humans depend on photosynthesis for the energy containing fossil fuels. It is the basis for drug industry. It is the basis for textile industry. Itis the basis for timber industry. AEB EeEN FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS The rate of a chemical reaction is how fast it occurs or progressing. The rate at which photosynthesis proceeds is limited by which ever factor is in short sup} This is the principal of limiting factors. Mainly photosynthesis is affected by: a) Light intensity b) Carbon dioxide concentration ¢) Temperature 4) Chlorophyll concentration a) Light intensity In low light intensities, the rate of photosynthesis is in direct proportion to increasing li But too much light decreases the rate since chlorophyll is destroyed. 12b) Carbon dioxide concentration Carbon dioxide is needed in the second stage of photosynthesis. ‘This is the main limiting factor of photosynthesis. An increase in carbon dioxide concentration increases the rate of photosynthesis. ¢) Temperature Reactions of photosynthesis are controlled by enzymes which are temperature sensitive. The optimum temperature is 25%. ‘Too much or too low temperatures decrease the rate since enzymes are affected negatively. 4) Chlorophyll concentration Chlorophyll traps and convert energy hence shortage in chlorophyll or low chlorophyll concentration reduces rate of photosynthesis. EXERCISE 1.7 a, Define the principle of limiting factors? b. Suggest some habitats or natural circumstances in which light intensity and temperature might be limiting factors? ©. ‘No life could be there without photosynthesis’. Justify this claim in an essay form? INVESTIGATIONS IN PHOTOSYNTHESIS The first substance plants make when they photosynthesise is glucose, Plants may turn a lot of this sugar into starch, which they can store for future use. When the level of glucose is low, plants convert this starch to glucose, a process called destarching. Before carrying out the following experiments, the potted plants must be destarched by putting them in the dark for about 48 hours. This is to make sure that the presence or the absence of starch at the end of the experiment is due to the set conditions. By putting them in the dark for 48 hours, they would be no photosynthesis, as sucb, all the stored starch would be converted to glucose and used in respiration. PRACTICAL ACTIVITIES 1, 18 LIGHT NECESSARY FOR PHOTOSYNTHESIS? MATERIALS 1. Adestarched plant 2. Black cello tape, clear plstic and two clips. nN tip black plastic ~ leat X leat ¥ Figure 12. Experiment for light and photosynthesis 3BMETHOD 1. Choose two leaves and stick a black cello tape on the middle of one leaf and stic. the middle of the other leaf with a clear plastic using clips. 2. Place the plant on the light for about 8 hours. 8. After which pluck the experimental leaves, remove the black cello tape and th clear plastic and test the leaves for starch. EXPECTED RESULTS A leaf which had a black cello tape is expected to show two patterns of colours. Where ther: was black cello tape, there will be brown -no starch and the remaining parts blue while th« other whole leaf would turn blue or black-starch present. CONCLUSION Light is necessary for photosynthesis. 2, IS CHLOROPHYLL NECESSARY FOR PHOTOSYNTHESIS? MATERIALS ‘One destarched variegated potted plant. Non-chiorophyit region Figure 13. Experiment for chlorophyll and photosynthesis PROCEDURE 1. Put the potted plant on the light for about hours. 2, Then pluck one leaf and test it for starch. RESULTS Only the parts that were previously white remained brown- no starch present unlike those that were green. CONCLUSION Chlorophyll is necessary for photosynthesis 3. IS CARBON DIOXIDE NECESSARY FOR PHOTOSYNTHESIS? MATERIALS One destarched potted plant, two transparent flasks, potassium hydroxide, and water. iestarch Potassium hydroxide to absorb carbon dioxide Figure 14, Experiment for carbon dioxide and photosynthesis PROCEDURE Choose two leaves on the plant. Put one leaf in a flask containing water and the leaf in a flask containing potassium hydroxide as shown above. Place the whole plant in the light for 6 to 8 hours. Pluck the chosen leaves and test them for starch. RESULTS ‘The leaf from a flask containing potassium hydroxide remained brown ~ no starch. The leaf from the flask containing water turned blue/black. Potassium hydroxide removes carbon dioxide from the atmosphere therefore no photosynthesis took place. CONCLUSION Carbon dioxide is necessary for photosynthesis. 4, IS OXYGEN PRODUCED DURING PHOTOSYNTHESIS? Gas coteetng—f-) Gas bubble~— Beaker, Test tube Water witn soot hyarogencarsonate Funnet — Water plant — Figure 15. Experiment for oxygen and photosynthesis A funnel is placed over a water plant in a beaker containing sodium hydrogen carbonated water and test tube inverted over the funnel stem. The funnel should be raised to allow circulation of water. The set up is placed in the sunlight, Bubbles of gas appear rising and collecting in the test tube. After sometimes the test tube is removed and a glowing splint is inserted.RESULTS ‘The glowing splint burst into flames. CONCLUSION Oxygen is produced during photosynthesis. REVISION QUESTIONS 1. Below is an experimental set up used to illustrate a certain investigation photosynthesis. Use it to answer the question that follow. The potted plants | previously left on the dark for 48 hours. Glass bell jars Potted plants Potasium hydroxide Glass beads (@) What is the aim of the experiment? (b) Why was it necessary to place the plants in the dark for 48 hours? (©) What was the use of the potassium hydroxide A? 2. Design an experiment to demonstrate that a green potted plant requires carbon dio to photosynthesize? |. Below is a diagram showing gas exchange between the atmosphere and the leaf. Stu and answer the questions that follow midrib (main vein) ‘What process in the leaf lead to this gas exchange? How is the leaf is adapted to this gas exchange Name two chemical. reactions that take place during the light dependent stag photosynthesis Explain how magnesium, nitrogen and phosphorus are important to plants 16CHAPTER 2 TRANSPORT IN PLANTS By the end of this topic, students should be able to: Identify tissues that are used for transport in plants. Describe structural and functional difference between the xylem and phloem. Describe processes of diffusion, osmosis and active transport. Explain factors affecting the rate of diffusion. Explain how substances are transported in the xylem and phloem. Explain the significance of diffusion, osmosis and active transport, Describe transpiration stream. Explain the importance of transpiration. Explain the factors affecting rate of transpiration. SANSA HE Higher piants have specialized long distant transport system called the vascular system which move substances more rapidly and efficiently from one point to another i.e. raw materials from the environment to photosynthetic sites and products from photosynthetic sites to storage organs and meristems, In plants, the Xylem and Phloem form the vascular system, This system requires a source of energy to function. In case of movement in the xylem the energy required comes from the sun where as the phloem has structures called Companion cells that produce energy through respiration. The movement of substances through the vascular tissue is called translocation. VASCULAR TISSUES A. Xylem tissue It consists of two types of cells a, Xylem vessels b. Xylem fiber |_| Hole between fe betwe ayler vessels Xylem vessel ‘element (one cet) seen Intact vessel viewed as if transparent Figure 16. Longitudinal sections of xylem vesselXylem vessels are dead remains of cylindrical cells that have lost their cross walls and are strengthened by lignin. Xylem vessels transport minerals salts and water from the soil to leaves. Xylem fibers are thought to have originated from tracheids but fibers are short and narrow. Xylem fibers offer support to the xylem vessels and plants at large. B. Phloem Phloem resemble xylem in possessing tubular structures for translocation, however unlil xylem, phloem tissue is made up of living cells. Tt consists of two tissues; 1. Sieve tissue. 2. Companion cells. Figure 17. Longitudinal section of a phloem Sieve tubes are individual cells arranged end to end to form long tubes .The cross walls ha small holes called sieve pores surrounded by sieve plates. Sieve tubes translocate main! organic food, sucrose. Companion cells are found along sieve tubes and produce energy for translocation. A VASCULAR BUNDLE (TISSUE) phloem cambium xylem- Figure 18, A vascular bundle 18DISTRIBUTION OF VASCULAR TISSUES (BUNDLES) IN MONOCOTS AND DICC A monocot, more properly monocotyledon is a flowering plant that has a single leaf in the and floral petals and other parts are in multiples of three. On the other hand, a dicotyled a flowering plant that has two leaves in the seed and whose subsequent leaves have a net of veins. A. Ina root Cambium Figure 19. Transverse section of a root showing the arrangement of the vascular tissues B. In stems epidermis vascular tissue Adicot stem {transverse section) Figure 20. Distribution of vascular tissues in dicot and monocot stems (transev sections) EXERCISE 2.1 a) Explain any two structural differences between xylem and phloem? b) State two functional differences between xylem and phloem? FORMS OF TRANSPORT IN PLANTS ‘There are four forms of transport; Diffusion. Osmosis. Active transport. Transpiration stream. Pepe Diffusion Ibis the net movement of particles from a region of high particle concentration to a regi Jow particle concentration. 19Particles diffuse to reach equilibrium. Importance of diffusion 1, Plants take up some salts from soil through diffusion. 2. Oxygen and carbon dioxide move in and out of plant leaves through diffusion. FACTORS AFFECTING RATE OF TRANSPIRATION 1. Size of particles The smaller the particles, the faster the rate of diffusion because of less mass. 2, Temperature An increase in temperature increases the movement of particles hence increasing diffu rate. 3. Concentration gradient It is the difference in concentration betwoon two regions. The bigger the differenc concentration gradient, the faster the rate of diffusion, 4, Surface area ‘The thinner the membrane, the bigger the surface area available for diffusion, the faster rate of diffusion. Active transport It is the net movement of particles from a region of low concentration to a region of | ‘concentration, Energy is required in this form of transport. Examples of active 1. Absorption of minerals from the soil to root cells. 2. Movement of sucrose from leaves to storage organs. EXERCISE 2.2 @) By what process would a nitrate ion move into a root hair cell when its concentration is higher in the root hair cell than in the soil? (i) Explain any three factors affecting diffusion? Osmosis It is a special type of diffusion in a sense that it involves movement of water molecules { a region of high water concentration to a region of low water concentration through set permeable membrane.water molecules pass Bormad through poresin membrane POmeees, dilute sugar solution FO concentrated sugar solution Figure 21. How osmosis occurs Ifa plant cell is in close contact with a solution of high solute concentration than its own, water leaves the cell by osmosis. Water is lost from the cytoplasm and vacuole through the tonoplast. The protoplast shrinks and eventually pulls away from the cell wall. This process is called plasmolysis. At this point the protoplast has stopped to exert pressure and the cell becomes very soft- this condition is called flaccidity. air space 5 cell membfane ra Figure 22, A plasmolysed cell If a plasmolysed cell is placed in pure water, water enters the cell by osmosis. At this point, the volume of the protoplast increases, pressure begins exerting against the cell wall. The wall _ becomes strong and relatively rigid. This condition is called turgidity. Figure 23, A turgid cell 2)Importance of osmosis 1. Ithelps plants to absorb water. EXERCISE 2.3 (@ James spreads too much artificial fertilizer on a maize planting station, After days a maize plant withered and dried. Explain this in terms of osmosis? (i) During photosynthesis when a plant cell is actively photosynthesizing, glu produced is quickly converted to starch. Explain 'the biological importance of th terms of osmosis? ii) In what way is diffusion similar to osmosis? Gv) Explain any four factors affecting diffusion? PRACTICAL ACTIVITY Investigation of turgor in potato tissue Materials: Potato tuber, razor blade, sugar, water, ruler, two test tubes Procedure 1. Prepare two slicos of potato tissue using razor blade. 2. Measure and record the length of the slices using a ruler. 3. Try to bend the 8. How do they feel? 4. Put one slice im a test tube filled with water and the other in a test tube filled sugar solution, Leave them to stand for 16-20 minutes. Results 1. Try to bend the slices again. How do they feel? 2 What happened to the slices in terms of osmosis 3, What name is given to the conditions in which both slices are in? MOVEMENT OF WATER AND MINERALS SALTS THROUGH A PLANT Most of the water entering the plant does so through root hairs. It travels across the cortex to the xylem. There are three possible pathways through which water uses to move the soil to the root xylem. => APOPLAST PATHWAY => SYMPLAST PATHWAY = VACOULAR PATHWAY Figure 24, Water pathways in a plant 221. Apoplast pathway It is a system of adjacent cell walls which is continuous throughout a plant. 2, Symplast pathway It is a system of interconnected protoplast in the plant. Water passes through cytoplasm. 8, Vacuolar pathway Water moves from vacuole to vacuole. WATER ASCENT IN THE XYLEM ‘There are two forces behind the ascent of water in the xylem namely; 1. Cohesion-tension theory According to this school of thought, water evaporation from the cells of the leaf is necessary for raising water from the roots. Evaporation results into a reduced water concentration in the cells next to the xylem as a result water enters these cells from the xylem sap. ‘The xylem vessels are full of water. When water leaves the xylem, tension is set up in the columns of water. This is transmitted back down the stream all the way to the roots by cohesion of water molecules that is sticking together of water molecules because they are polar. Water molecules also tend to stick to the walls of xylems inside by a force called adhesion. 2, Root pressure If pressure is applied to pure water or solution, water molecules are forced to move from one place to another. For example, if water enters root cells by osmosis, pressure builds up inside cells and this forces water into the xylem vessels and ultimately up to the leaves. Minerals salts enter plant together or as dissolved in water. They are also absorbed by active transport. TRANSPIRATION Itis the loss of water in form of water vapour from the surface of plants mainly leaves through stomata. When stomata are closed, transpiration is greatly reduced. {Transpiration may also occur in the lenticels i.e. small openings on plant stems. ay ve :. Absorbed Water from inside cell is forced outwards through cell walls by turgor pressure. From. » the outer surface of cell walls, this water evaporates into the intercellular space and diffuses a out through stomata to the atmosphere. portance of transpiration ty" Transpiration stream Evaporation of water from leaf cells due to transpiration results into a fall of the cells turgidity Pknd a rise in the concentration of their cell sap. Consequently, the cells’ osmotic potential decreases. In this condition, cells will start absorbing water from neighbouring cells and | eventually from the xylem vessels of the leaf. When water leaves xylem vessels, tension is set up in the columns of water. This tension draws water up the vessels of the stem from the roots by cohesion of water molecules. This 23continuous flow of water from the roots to leave through stems due to transpiration is ¢ ‘Transpiration Stream. Figure 25, The transpiration stream 2. Cooling Evaporation of water from plants require energy therefore result in cooling similar to sweat in human beings. 3. Transport of salts As water enters plants, salts are also absorbed and transported. 4. Uptake of water As water evaporates, cohesions results into continuous flow through the plant he absorption of water from the soil. EXERCISE 2.4 i, Trace the path taken by water from the soil through the roots, stem and leaves to atmosphere. Explain the forces behind its movement at each stage? Factors affecting the rate of transpiration Plants show many features (adaptation) which enable them to reduce loss of water transportation in dry conditions. These features are called xeromorphic. Below are som: the environmental factors affecting transpiration. A. Temperature It has the greatest effect. The higher the temperature, the greatest the rate of evaporation from the cell of mesop! layers hence the fastest the rate of transpiration. Some plants have purple colored leaves due to thick cuticle that reflect light hence red temperature 24B, Humidity Humidity is the amount of water vapor in the air. The lower the humidity, the faster the rate of evaporation from leaf cells hence faster rate of transpiration. Some plants have sunken stomata where a high humidity can build up and reduce transpiration. C. Wind speed Windy condition results into increased evaporation of water molecules hence increase the rate of transpiration. Some plants have hairs and sheath that trap still air hence reducing transpiration, D. Light Light is responsible for structural opening of the stomata. Transpiration occurs mostly through stomata. The greater the light intensity, the more stomata open hence increase rate of transpiration. Most leaves have more stomata in shady areas like lower part of a leaf to reduce transpiration. Measuring the rate of transpiration A potometer is a piece of apparatus designed to measure the rate of water uptake by a cut shoot. It does not measure transpiration directly but since most of the water taken up o1 abeorbed is transpired, then these two processes are closely related. Below is a diagram of a potometer. Figure 26. The potometer To measure the rate of transpiration, measure the distance covered by the air bubble and divide by time taken. EVIDENCE THAT PHLOEM TRANSPORTS ORGANIC FOOD (SUCROSE) ‘A. Ringing or girdling experiments ‘This involves removal of a ring of a bark from a stem a process called girdling. This removes phloem tubes and leaves xylem tubes unharmed. Removing the bark above the soil cause reduced root growth and swelling of tissue above the side. 25EXERCISE 2.5 (@) Give a reason why cutting a deep ring of bark from a tree stem cause its death? (ii) For each of the following pairs of conditions, suggest which one will produce the fastest rate of transpiration and explain your answer. a. Hot weather or cold weather b. A dry atmosphere or a humid atmosophere c. Astill day or windy day d. A bright sunshine or dull weather ROOT HAIRS Root hairs are fine growth of epidermal cells from the outer cells of plant roots that resemble hairs. These elongated epidermal cells increase the surface area of roots to improve absorption of water and minerals, See figure below. ——— a Epidernial cells Figure 27. The root hair Adaptation of root hairs for absorption 1. Long and narrow and numerous ~increase the surface area for absorption. 2, Cytoplasm of root hairs has more solutes-this lowers the water potential root hair cells hence water moves from the soil to inside. 3. Root hairs have vascular tissues ~transport water and mineral salts. PRACTICAL ACTIVITY Investigation: How do plants take up water? Materials 8 young pea plants, one with dried leaves, any cooking oil, 3 test tubes, test tube stand, Vaseline, pencil. Procedure 1. Half fill each of the test tubes with water and label your test tubes. 2. In test tubes A and B, put the small pea plants in (one in each). Smear the roots of a pea plant in test tube B. Put the small pea plant with dried leaves in test tube C. Fill the three test tubes with water of the same level. Cover the surface of water in all three test tubes with cooking oil. Mark the positions of ‘the water in each with glass marker. Leave the experiment in a safe place to stand for 8- 12 hrs in a bright sunny day.Results Water level Test tube A Test tube B ‘Test tube C First day Mm Mm ‘Second day Mm Mm Difference Mm Mm Questions 1. What is the purpose of spreading cooking oil on the water surfaces? 2, What has happened to the water levels in each test tube. 8. What is the purpose of smearing Vaseline on the roots of test tube B? 4, What is the aim of test tube C REVISION QUESTIONS L Define the following terms as used in transport in plants. a. Transpiration stream. Bb, Plasmoly . Flaceidity. . A solution of salt is separated from a solution of sugar of equal concentration. Discuss whether Osmosis would take place and justify your conclusions? Explain the following with respect to Osmosis a. If too much fertilizer is spread on a maize planting station, the maize plants wither and die. b, In an actively photosynthesing cell, the sugars being formed are quickly converted to starch. In an essay form, describe the xeromorphic features which plants posses to reduce water Joss due to transpiration. Describe an experiment you would carry out to measure the uptake of water by a leafy shoot? Define osmosis? How does a root hair cell absorb water and mineral salts? Describe an experiment to illustrate osmosis. ‘Two cells of plants have different cell sap concentrations. Cell A has cell sap with dilute solution while cell B has cell sap with more concentrated solution. Which bas a higher ‘osmotic potential? Why?CHAPTER 3 HUMAN DIGESTIVE SYSTEM By the end of this topic, students should be able to; State function of carbohydrates, proteins, lipids, vitamins, mineral salts and water. State chemical composition of different food substances, State different digestive enzymes and the food substances they work on. List products of chemical digestion. Describe properties of enzymes. Describe process of absorption of food substances. Describe adaptation of small intestines to their function. State functions of the large intestines. State the fate of digested food. 10. Explain problems associated with the digestive system. 11.Carry out investigation on the enaymes. SONAMASN Nutrition is the acquiring of energy and raw materials needed to form cells and to maintain metabolism. This means that there are two basic nutrition requirements necessary for living things- energy and building materials. These are supplied in the form of chemicals known as nutrients. Food stuffs are substances that supply us with these nutrients. Diet is the quality and nature of food stuffs we eat; thus, which nutrients and how much. Digestion is the mechanical (physical) and chemical break down of large organic molecules into smaller, simpler soluble molecules that can be absorbed and used in the body. Digestive System is a group of connected organs whose purpose is to break down, or digest, the food we eat. The simple molecules travel through the bloodstream to all of the body's cells, which use them for growth, repair, and energy. CHEMICAL COMPOSITION AND FUNCTIONS.OF DIFFERENT FOOD NUTRIENTS: Basically, there are six different food nutrients; 1. Carbohydrates. Proteins. Vitamins. Mineral salts. Water. Lipids. ae oN 28Carbohydrates They are substances containing elements: carbon, hydrogen and oxygen. ‘The general formula is C,(Hz0)y where x and y are variables. They are divided into three main groups; a) Monosaccharides. b) Disaccharides. ©) Polysaccharides. Monosaccharides These are single sugar units, General formula is (CH20)a where n is from 3-7. Examples are glucose (CsHi20s) and galactose (CsH1205). Digestion of carbohydrates ends up producing monosaccharides. Properties of monosaccharides 1. All are soluble in water. 2. Have faint sweet taste, 3, Alll react with oxygen to release energy hence alll are reducing sugars. Functions of monosaccharides 1. Source of energy. 2. Synthesis of disaccharides. 3. Synthesis of polysaccharides Disaccharides Double sugars are formed when two monosaccharides combine in a process known as condensation-a water molecule is released; CeHi206 + CoHiz0e———=—> _ CroHa20n1 + H20 Examples are sucrose = glucose +fructose Maltose = glucose +glucose Lactose = glucose + galactose perties of disaccharides a. All are soluble in water. b. Very sweet. c. Maltose and lactose are reducing sugars while sucrose is not. nctions of disaccharides 1. Source of energy. 2, Forms of transport in plante (sucrose).Polysaccharides These are polymers of monosaccharides ie. made up of more than 70 molecules of monosaccharides. Examples are starch, cellulose, and glycogen. Properties of polysaccharides 1. Insoluble in water. 2. Not sweet. 3, Non reducing sugar. Functions of polysaccharides 1. Food and energy stores e.g. starch, glycogen. 2. Form part of plants cell walls. Proteins ‘These are organic complex substances consisting of carbon, hydrogen, oxygen, phosphorus, sulfur, and nitrogen. The basic unit is an amino acid. Thore are two types of amino acids. a) Essential amino acids. ‘b) Non ~essential amino acids. ‘Amino part R Figure 28. The structure of an amino acid Properties of proteins 1. Some are soluble in water e.g. hemoglobin while others are not. 2. They are affected by temperature, ph ete. When the chemical digestion of proteins is complete, amino acids are produced. Functions of proteins 1. Growth and repair of worn out cells. 2, Formation of other body proteins for example antibodies and hemoglol 3. Source of energy. 30Lipids ‘These are organic compounds divided into fats and oils. Fate are soft and greasy at ordinary tomperatures, whereas oils are liquid. Contain elements carbon, hydrogen, oxygen but the ratio of hydrogen to oxygen is greater than 2s, ‘The basic unit is fatty acids and glycerol. Funetions of lipids 1. Source of energy. 2, Act as insulation under the skin. 3. Solvents for some vitamins for example vitamins A, D, and E. 4. Form part of cell membrane. 5, Form components of some hormones. EXERCISE 3.1 8) Give two chemical differences between polysaccharides and disaccharides? b) Give one example of a polysaccharide? ©) Define reducing sugars? ) Give two examples of reducing sugars? ©) State any two importances of polysaccharides? f) Describe the chemical differences among carbohydrates, proteins and lipids? PRACTICAL ACTIVITY: FOOD TESTS: A. Test for starch Materials: food stuffs to be tested, test tubes, iodine solution. Procedure 1. Crush the food stuffs to form fine particles. 2. Put the crushed particles in test tubes and add water to dissolve. 8. Add few drops of iodine in each test tube. Results What do you observe? OTE: dark blue color is a characteristic indicator of the reaction between starch and fodine. Test for reducing sugars terials: food stuffs to be tested, Benedict’s solution, test tubes, Bunsen burner, jure: 1. Crush the food stuffs to form fine particles. 2, Put the crushed particles in test tubes and add water to dissolve. 8. Add 2-3 drops of Benedict's solution. Heat the mixture for some time. itate indicates presence of reducing sugars. 3a©. Test for non reducing sugars. Materials: food stuffs to be tested, Benedict's solution, test tubes, Bunsen burner. Procedure: 1. Crush the food stuffs to form fine particles. 2. Put the crushed particles in test tubes and add water to dissolve. 8. Add 8 ml of Hydrochloric acid followed by 3m of sodium hydroxide. 4. Add 2-3 drops of Benedict's solution. 5. Heat the mixture for some time. Results Red precipitate indicates presence of reducing sugars. Question 1, What is the reason of adding 3ml of hydrochloric acid and sodium hydroxide in step 3? D. Test for proteins Materials: food stuffs to be tested, test tubes, solution. Procedure 1, Crush food stuffs to form fine particles. 2. Put the fine particles in a test tube and add few drops of water to dissolve. 8. Add 5ml of sodium hydroxide. 4, Add 5ml of copper sulphate solution, ite sodium hydroxide, copper sulphate Results A purple color is indicative of proteins. E, Test for lipids Materials: food stuffs to be tested, a clean plain paper. Procedure 1. One by one, rub the food stuffs on a paper and wait for about 3 minutes. Results Translucent spot indicate presence of lipids. DIGESTIVE ENZYMES Chemical digestion is effected by special chemicals called enzymes. An enzyme is defined as a biological catalyst. A catalyst is a substance which speeds up a chemical reaction but remains unchanged itself at the end. The substances which enzymes work on are called substrates. Once a reaction is complete there will be products and enzymes. Properties of enzymes 1. Allare proteins in nature. 2. They are catalysts-speed up chemical reactions. 3. They are specific~one enzyme for one chemical reaction only. 324. They are affected by temperature. The optimum temperature of most human enzymes is 37%. 5. They are affected by P#5-have optimum P#, PRACTICAL ACTIVITIES ON ENZYMES A. Aim: To investigate the digestive action of saliva on starch. Procedure 1 Rinse the month to remove traces of food. 2, Using a test, collect 3 ml of saliva from your mouth. 3, Put 2mls of 2% starch solution in 2 test tubes, test tube A and B. 4. Add Iml of saliva to each test tube, test the contents of test tube A for starch and leave the test tube B for sugar (Benedict reagent) test. 5. Write the results in the table below. A 7 B Starch test, ‘Sugar test Question 1. What do you conclude from thi 2, Suggest a contro! for this experiment? B, Aim: To investigate the effects of pH on an enzyme reaction. Procedure: y 1. Collect six test tubes and label them A-F, 2, Fill each test tube with 5ml 1% starch solution 8. Put 10 drops of 0.1M sodium bicarbonate in A, 4 drops of the same in B. Then put 6 drops of 0.1M hydrochloric acid in D, 7 drops of the same in E and 8 drops of the same in F. 4. Collect saliva and put iml in each test tube. 5. After 5-10 minutes, test each test tube for starch and write the results in the table below TEST TUBE, STARCH TEST RESULTS ion it do you conclude from the results above? fo investigate the effect of temperature on an enzyme reaction jure |. Put 2ml of 2% starch solution in three test tubes labeled A to C. Place test tube A in a beaker of ice water, test tube B in a beaker of cold tap water and test tube C in a beaker of warm water at about $6-40°c. 338. Then add Lml of saliva in each test tube. 4. After 5-10 minutes, test the contents from each test tube for starch and write the results in the table below. TEST TUBE A B c (RESULT, What do you conclude from the above results? EXERCISE 3.2 I. Saliva is swallowed together with different food substances including carbohydrates. Give the reason why there is no digestion of carbohydrates in the stomach? ‘Types of digestive enzymes and the food substances they work on ‘There are three categories; a) Proteases —digest proteins to amino acids. b) Amylases -digest carbohydrates to monosaccharide. ©) Lipases — digest lipids to fatty acids and glycerol. Proteases 1. Pepsin — converts proteins to polypeptides. 2. Trypsin ~ converts polypeptides to peptides. 3, Peptidase ~ converts peptides to amino acids. 4, Rennin- solidify milk so that it remains in the stomach long enough to be digested fully by other protein digesting enzymes. Amylases 1. Salivary amylase /ptyalin — converts cooked starch to maltose. 2. Pancreatic amylase ~converts uncooked starch to maltose. 3. Maltase ~ converts maltose to glucose. 4, Sucrase — converts eucrose to fructose and glucose, 5. Lactase- converts lactose to glucose and galactose. Lipases Those are enzymes that convert lipids to fatty acids and glycorol, Minerals salts and vitamins are needed in small amount and their importance is to maintain metabolism. EXERCISE 3.3 I. Describe an experiment you would conduct to show that germinating maize seeds contain enzymes that digest starch? 34HUMAN DIGESTIVE SYSTEM “The human digestive systems consist of the following parts/structures: 1. Mouth. Esophagus. Stomach. Small intestines. Large intestines. Rectum. Anus and other accessory structures like the liver and pancreas. NPA ew % Figure 29. The human digestive system Food is taken in (ingested) through the mouth where it is chewed to make the food perfectly jsmaller and at the same time to mix the food with saliva, which acts as a lubricant. the mouth there are salivary glands which secrete saliva. teeth tear and grind food into smaller particles and the tongue moves the food and forms hherical masses called boli (bolus -singular) ready for swallowing. The bolus is pushed by the ie from the mouth to the pharynx, a cavity behind the mouth. In this cavity, there is an ning to the Jungs called larynx closed by an epiglottis that closes when swallowing. esophagus is a muscular tube leading to the stomach. The stomach is situated below the iaphragm on the left of the abdominal cavity. It is about 25 cm long and 10 cm in diameter jwhen full. The esophagus enters the upper end of the stomach. The upper end is closed by a Hh. 35cardiac sphincter and the lower end is closed by the pyloric sphincter which controls spillge of food from the stomach. The lining of the stomach contains glands that secrete gastric juices. When the food is completely mixed with gastric juice; it forms a creamy liquid substance called chyme. Connected to the lower end of the stomach is the small intestine which consist of three parts; duodenum, jejunum and ileum, in that order ‘from the stomach. Two ducts enter the duodenum, the bile duct from the liver and pancreatic duct from the pancreas. In humans these ducts join to form one common duet, The ileum in humans is about 6m long. Throughout its length, the inner surface of the illeum is covered with many finger-like projections called villi. The circular and longitudinal muscles of the alimentary canal contract and relax alternately to push the chyme through and this process is called peristalsis. Glands in the mucus lining of the ileum secrete suceus enterricus which finalize chemical digestion. The ileum is joined to the large intestine about 15 m and consists of the caecum, colon and reetum. Attached to the caecum is a nervous tube called appendix. In humans it plays no role in digestion. The lower end of the rectum is closed by the anus surrounded by anal sphincter. The function of the rectum is to store waste materials called feces until it is egested. THE PROCESS OF DIGESTION There are two forms of digestion; 1. Physical digestion, 2. Chemical digestion. Physical digestion It is the process whereby large food particles are broken down mechanically into smaller particles by physical forces. The importance of physical digestion is to create a large surface area of food substances for enzymes to act on Properties of products of physical digestion 1. No new substance is produced, that is, the fundamental nature of the components is not changed. 2. Food stuffs are made very small hence creating a large surface area for enzyme action. Physical digestion is brought about by. 1. Action of teeth in the mouth. 2. Peristaltic movement of the alimentary canal. 3. Churning movement of the stomach. 4. Action of bile. Bile break down large fat (lipid) globules into smaller particles -this process is called emulsification. 36Chemical digestion It involves the use of chemicals called enzymes produced by glands. These enzymes are found in watery juices called digestive juices. ‘There are four types of digestive juice; 1. Saliva. 2, Gastric juice. 3. Pancreatic juice. 4, Succus entericus. Saliva It is produced by salivary glands in the mouth. It is alkaline. It contains the following: 1, Water — soften food stuffs. 2. Sodium hydroxide~ makes the food alkaline and provides an optimum pH for ptyalin to work best. 3. Mucus — lubricate food for easy swallowing. 4. Ptyalin (salivary amylase) that converts cooked starch to maltose. Gastric juice It is produced by the walls of the stomach. It contains the following. 1. Pepsinogen. 2. Hydrochloric acid 3. Rennin. 4. Mucus. Hydrochloric acid activates pepsinogen to pepsin, Hydrochloric acid also kills germs taken together with food, Pepsin converts proteins to polypeptide: Rennin is an enzyme found in the stomach lining of cows and newborn babies. Its main function is to solidify milk so that it (milk) remains long enough to be digested by other protein-digesting enzymes. ‘Mucus prevents the walls of the stomach from being digested by pepsin and badly damaged by hydrochloric acid. Pancreatic juice It is produced by the pancreas. Tt contains the following; L. Trypsinogen. 2. Sodium hydroxide. 3. Lipase. 4. Pancreatic amylase. 37Sodium hydroxide activates trypsinogen to trypsin. Trypsin converts polypeptides to peptides. Lipase converts lipids to fatty acids and glycerol. Pancreatic amylase converts uncooked starch to maltose. Succus entericus Produced by the inside lining of the ileum. Contains the following; 1, Peptidase 2. Lactase, 3. Lipase. 4. Maltase. 5. Sucrase. Peptidase converts peptides to amino acids. Lipase converts lipids to fatty acids and glycerol. Suerase converts sucrose to glucose and fructose. Lactase converts lactose to glucose and galactose. Maltase converts maltose to glucose. EXERCISE 3.4 (i Imagine that you are shrinking and shrinking in size until you can step inside one cell of a piece of fatty meat. All round you are large fats molecules. Cling onto and sit astride a fatty acid and glycerol molecules. Describe your adventures from the moment someone bites the meat piece until you and the fatty acid and glycerol molecule find yourself in the ileum. Copy and complete the table below: Part ‘of | Juices secreted [What the juices [What is [Any other digestive contain digested points system _ oeeeon Mouth Stomach ee Small intestine Large intestine Colon Rectum ABSORPTION It is the process by which the final products of digestion are taken up into the blood stream. ‘This happen through certain structure in the the ileum called villi. 38Figure 30. The villus Glucose, fructose, galactose (monosaccharides), amino acids, water, vitamins, salts are absorbed into the capillaries. Fatty acid and glycerol are absorbed into the lacteal to the lymphatic system. From the capillaries the absorbed food substances go to the liver through the hepatic portal vein. From the lacteals fatty acids goes to lymphatic system and then to the liver. Adaptation of the villus for absorption . They have a network of capillaries. These capillaries absorb and transport glucose, amino acids salts and vitamins. Presence of the lacteal. The lacteal absorbs and transport fatty acids and glycerol. . The epithelial walls of the villi are thin therefore the absorbed food substances move a shorter distance after being absorbed. |. Epithelial cells have numerous mitochondria that produce energy for absorption. ADAPTATIONS OF THE SMALL INTESTINE FOR THEIR FUNCTION A. For digestion 1. It produces enzymes that digest food substances. 2. It has an optimum P* for the different enzymes. 3. It is very long ~this creates a large surface area for digestion and absorption. B. For absorption . Itie very long. .. Rich in blood vessels that transport absorbed food substances. . It has villi that absorb digested food substances. |. ‘The epithelial wall of villi is thin and contains numerous mitochondria that produce energy for absorption. EXERCISE 3.5 a. State two main functions of the ileum? b. Explain how a villus is adapted to its function? 39THE LARGE INTESTINES A watery residue of indigestible food and digestive juices remains unabsorbed. This residue leaves the ileum of the smail intestine and moves by peristalsis into the large intestine, where it spends 12 to 24 hours. The large intestine forms an inverted U over the coils of the small intestine. It starts on the lower right-hand side of the body and ends on the lower left-hand side. The large intestine is 1.5 to 1.8 m long and about 6 cm in diameter. Funetions of the large intestines The large intestine serves several important functions. 1. It absorbs water—about 6 liters per day—as well as dissolved salts from the residue passed on by the small intestine. 2. Bacteria in the large intestine promote the breakdown of undigested materials and make several vitamins, notably vitamin K, which the body needs for blood clotting. ‘The large intestine moves its remaining contents toward the rectum, which makes up the final 15 to 20 cm of the alimentary canal. The rectum stores the faeces—waste material that consists largely of undigested food, digestive juices, bacteria, and mucus—until elimination, ‘Then, muscle contractions in the walls of the rectum push the faeces toward the anus. When sphincters between the rectum and anus relax, the faeces pass out of the body in a process called defaecation. WHAT HAPPENS TO THE END PRODUCTS OF DIGESTION AFTER ABSORBTION Assimilation It is the process by which absorbed end products of digestion are taken up and used by the body cells. Glucose is used for respiration, Excess glucose is converted to glycogen and stored. Energy produced from respiration is used by the body to power al its activities. Fatty acids and glycerol are used to form fats and some parts of the cell membrane. Amino acids are used to form various bodily protein e.g. hemoglobin. EXERCISE 3.6 i, Trace the path taken by an amino acid and a fatty acid and glycerol after being absorbed in the intestine to the a) Liver b) Muscle cell ii, Explain any two functions of the large intestines? THE LIVER The liver is the largest internal organ of the body located below the diaphragm. Basically it is an organ of homeostasis. It controls many metabolic processes essential for maintaining a constant blood composition. Functions of the liver related to digestion 1. Storage of Some nutrients e.g. glycogen, vitamins and minerals, 2. Produce bile which is stored in the galll bladder. 8. Control sugar level in the body under the influence of insulin and glycogen. 4, Control lipid levels, 5. Control of proteins by deamination and transamination. 40Figure 31. The liver, pancreas, stomach and small intestines Deamination One of the functions of the liver is protein metabolism. The body is not capable of storing excess amino acids as it does with glucose. Instead excess amino acids are broken by the liver cells to produce urea, a process called deamination. During deamination, an amino acid is oxidized by oxygen and this results in the removal of the amino group (-NHz) and leaves an acid part. The acid part is converted to a carbohydrate and used as a source of energy. The amino group is converted to ammonia (NH). Since ammonia is very much toxic; it is immediately reacted with carbon dioxide to produce urea and water. PROBLEMS ASSOCIATED WITH DIGESTIVE SYSTEM 1, Constipation Constipation, occurs when the large intestine absorbs too much water because food residues are moving slowly. As a result, the faeces become hard and dry, which may make elimination difficult. It is also caused by: a. Lack of roughage or fiber in the diet. b. Stress and anxiety. c. Not drinking enough water. d. Sickness and some medicines. 2. Diarrhoea Diarrhoea is the frequent elimination of loose, watery faeces. It is a symptom of many disorders that occurs when the large intestine is irritated or inflamed by parasites. As a result, food residues move through it too quickly for it to absorb the excess water. It is caused by germs mostly viruses and bacteria. an3. Nausea Nausea is uneasy sensation in the upper abdomen, sometimes preceding the act of vomiting. Nausea is frequently associated with feelings of faintness, cold perspiration, weakness, and vertigo. Vertigo is a condition in which somebody feels a sensation of whirling or tilting that causes loss of balance. It may be caused by a number of factors, including anxiety and exposure to certain chemical fumes. In addition, nausea can be a symptom of an underlying physical problem, such as appendicitis. 4. Peptic ulcers ‘These are wounds in the alimentary canal. The direct cause of peptic ulcers is the destruction of the gastric or intestinal mucosal lining by hydrochloric acid, an acid normally present in the digestive juices of the stomach. As a result, protein digestive enzymes start eating the intestinal muscles causing small wounds. Infection with the bacterium Helicobacter pylori plays the key role in causing both gastric and duodenal ulcers. 5. Indigestion Indigestion, also called dyspepsia, is a condition that occurs when the normal process of digestion is disturbed. The symptoms of indigestion include stomach cramps, belching, and a feeling of fullness. Nausea, vomiting, bloating, gas, and heartburn, which is a burning sensation in the oesophagus, sometimes accompany these symptoms. In most cases, indigestion is caused by poor eating habits such as eating too much or too quickly, swallowing air while eating, or not chewing food properly. It may result from eating excessive amounts of fatty foods, improperly cooked foods, or vegetables such as cabbage, onions, and radishes. It may also be caused by emotional upsets. Indigestion caused by any of these factors can usually be treated by taking over-the-counter antacids. 6. Heart burn Heartburn is condition characterized by a burning feeling in the chest and a sour or bitter taste in the mouth. Heartburn typically develops when the acidic contents of the stomach flow back into the oesophagus, the muscular tube that carries food from the throat to the stomach. Heartburn is more common in pregnant women because of the pressure the expanding uterus exerts on the stomach. Normally the contents of the stomach are held in place by the lower oesophageal sphincter, a muscle at the lower end of the oesophagus that allows food to pass into the stomach. If this muscle relaxes, or is too weak, the food can flow out of the stomach and back into the oesophagus. 7. Appendicitis Appendicitis is an inflammation of the appendix, a tube-like pouch about 9 cm long that branches off the large intestine. It occurs most commonly among children and young adults EXERCISE 3.7 i, Describe five problems associated with the human digestive system? anREVISION QUESTIONS 1, Distinguish between physical and chemical digestion. 1. Protein digesting enzymes are secreted into the alimentary canal in an inactive form. a. Suggest a reason for this. b, Name two such enzymes ¢. State how each enzyme is converted into an active form? State one end product of digestion transported by the lacteal Describe the role played by acids and bases to digestive enzymes. Name one such acid and a base? Figure below shows an experimental set up in a laboratory. Use it to answer the questions that follow. Uncooked starch solution meen Visking tube a, What was the aim of the experiment? b. What type of membrane is the visking tubing? ¢. Suggest a control for the experiment? d. What could be the results if the solution is tested for starch? Explain? 6. Figure below shows structure of a certain food substance. Use it to answer the questions that follow. amino acid—___ peptide bonds a, Name the food substance? b. Mention three enzymes that could digest the food substance in humans? 7, Define deamination? 8, Explain any three functions of the liver associated with digestion?CHAPTER 4 HUMAN CIRCULATORY SYSTEM By the end of this topic, students should be able to; |. State the functions of the circulatory system. 2. State the types of blood cells. 2. Describe the structure of blood cells. 1. Relate structure of blood cells to their function. ”. Explain the role of haemoglobin in oxygen transportation. 7. Compare the structure of arteries, veins and capillaries. . State the relationship between structure and function of each type of blood vessel. 2. Describe the blood clotting process. 7. Describe the structure of the heart. 10. Explain the effects of physical activity on pulse rate. 11.Describe the lymphatic system. 12. Explain the importance of the lymphatic system. 18. State the problems associated with the circulatory system. ‘The purpose of a human blood circulatory system is to provide a quick mass flow of materials from one part of the body to another over distances where diffusion would be too slow. On reaching their intended end, the materials must be able to pass through tissues. Similarly the materials produced by the tissues must enter the circulatory system. CHARACTERISTICS OF EVERY BLOOD SYSTEM 1. A cireulatory fluid -blood. 2. A contractile pumping device to pump or provide force with which the fluid circulates-the heart. 3. Tubes through which the fluid can cireulate-blood vessels. FUNCTIONS OF THE CIRCULATORY SYSTEM 1. Transportive functions a) Transport oxygen from lungs to the tissues. b) Transport carbon dioxide from tissues to the lungs. ©) Transports excretory products to the excretory organs. 4) Transport digested food from the small intestines to various parts of the body. ©) Transport hormones from glands to target organs. 2. Defensive functions Defense against diseases -this is achieved in three ways; a) Clotting of blood-prevents blood loss and entry of disease causing organisms. b) Phagocytosis-white blood cells engulfing germs, a4c) Immunity — antibodies and lymphocytes. 3. Homeostatic functions a) Maintenance of a constant blood solute potential and P# plasma protein activity. b) Control of body temperature in distribution of heat. EXERCISE 4.1 (@) Write an essay describing the three main functions of the blood circulatory system PARTS OF HUMAN CIRCULATORY SYSTEM It consists of; 1. Blood, 2. Blood vessels. 3. Heart. Blood Blood is a liquid tissue consisting of several types of cells which are found bathed in a fluid matrix called plasma. ‘An adult human has approximately 5.5 1 of blood. Plasma A pale straw colored liquid that consist of 90% water and variety of substances in a solution suspension of which the major ones are plasma proteins prothrombin and fibrinogen, enzymes. Tt also has dissolved substances like digested food particles, hormones and salts. Blood left in a test tube would appear as below; Figure 82. Blood left in a test tube to settle Blood cells There are three types of blood cells; 1. Red blood cells. 2. White blood cells. 3. Platelets. 45,- ye Eosinophils Basopnis Fe = Monocytes Enythrocytes Figure 33. Types of blood cells Red blood cells Red blood cells are also known as Erythrocytes. They appear as circular, biconcave discs and very thin. They do not have a nucleus instead they are packed with an oxygen carrying protein called hemoglobin which gives blood its red color. The lack of nucleus makes more room for hemoglobin. Do not have mitochondria which make more room and hence make them not to use oxygen. 7 Red blood cells are produced in all bones in infants and in scapula pelvis, sternum ribs, and vertebrae in adults. Red blood cells have relatively short life span (three months). Figure 84. The red blood cells Functions of red blood cells 1. Transport oxygen in form of oxy-haemoglobin. 2. Transport carbon dioxide in form of carbamino-haemoglobin. 46Transport of carbon dioxide Carbon dioxide is carried in three different ways: 1. Ina solution as carbonic acid (HaCOs). 2. Combined with protein-carbon dioxide combines with the amino group of haemoglobin to form of a compound called carbano-haemoglobin (HHbNH-COOH). 3. As hydrogencarbonate-carbon dioxide produced by the tissues combines with water to form carbonic acid catalysed by an enzyme called carbonic anhydrase. Then carbonic acid dissociates into hydrogen and hydrogencarbonate ions. Then hydrogencarbonate ions combine with sodium in the plasma to form sodium hydrogencarbonate, When blood containing sodium hydrogencarbonate reach the lungs, the reverse process occurs and carbon dioxide is released. White blood cells They are also known as Leukocytes. They are large and less numerous than Red blood cells. Have a nucleus, no hemoglobin and have mitochondria Based on the shape of the nucleus, they are divided into two main groups. @ — Glanulocytes Have a lobed nucleus. Examples are: (a) Neutrophils Protect the body by engulfing bacteria in a process called phagocytosis hence also known as phagocytes. See figure 32 above. Figure 35. A phagocyte during phagocyto: (b)Eosinophils They are responsible for allergic responses. See figure 82 above. (©) Basophils Produce heparin to prevent clotting of blood and histamine responsible for inflammation. See figure 32 above. (ii) Agranulocytes These are white blood cells that have a spherical nucleus. These secrete special chemicals called antibodies that attack foreign materials to the body. Examples (@ Monocytes. See figure 32.(ii) Lymphocytes (produced in the lymphatic system). See figure 32. NB: White blood cells are produced in long bones. Platelets They are also known as thrombocytes. ‘These are fragments of cytoplasm formed by the degeneration of large cells in the bone marrow. They do not have a nucleus. Functions of platelets Platelets are responsible for blood clotting. Blood clotting It is the process by which a mesh of fibrin fibers is formed at cut surfaces. Process Breaking of platelets at cut surface due to the presence of air (oxygen). Platelets debris combines with calcium ions, Vitamin k to form thromboplastin. Thromboplastin converts prothrombin to thrombin. Thrombin together with soluble enzymes (factors viii) convents fibrinogen to fibrin, a clot. Beir EXERCISE 4.2 (@ Write an essay stating the five components of blood and explain their functions? (i) How the circulatory system helps to prevent bacteria entering into the body through a skin cut? Blood vessels ‘These are avenues through which blood passes as it is circulating. ‘There are three types of blood vessels; 1. Arteries. 2. Veins. 3. Capillaries. Arteries Lumen Figure 36. Structure of an artery 48‘Transport blood away from the heart. Their lumen is small and elastic muscle wall is thick. They don't have valves. Pressure of blood is high and there is thin pulse. Blood flow is rapid and the blood is bright red. They have low blood volumes. ‘Transport oxygenated blood except the pulmonary artery. Veins ‘Transports blood towards the heart. ‘They have a large Lumen. Valves are present at intervals-these valves prevent back flow of blood. Valve Figure 37. Longitudinal sections of veins showing valves Pressure low and pulse is present. Blood flow is slow and the blood is dark red. To help the blood move along, most veins are located between the muscles. As muscles contract, they squeeze in on the vein and push blood forward. They have a high blood volume. ‘Transport deoxygenated blood except the pulmonary vein. EXERCISE 4.3 I. Suggest three ways in which blood moves in veins? Il. How does the pulmonary artery differ from all other arteries in the body? Capillaries These are blood vessels that link arteries to veins. ‘They are sites of exchange of materials between blood and tissues. They are one cell thick. Pores Tissue fluid. Figure 88. The capillary ‘They don’t have valves.Blood pressure falls in these vessels. They have high blood volume. ‘They contain mixed oxygenated and deoxygenated blood. Blood flows slowly, EXERCISE 4.4 Copy and complete the table below contrasting arteries, veins and capillaries Feature Arteries Veins Capillaries [What is its Function ‘Thickness of walls Elasiticity of walls Size of lumen Valves Tissue fluid Tissue fluid is a watery liquid which resembles plasma but it does not have plasma proteins (Prothrombin and fibrinogen). Tissue fluid is formed when blood passes through capillaries. As blood is passing through capillaries, pressure builds up and this forces smaller substances to leak through the walls of cayillaries except large particles- blood proteins. Leaked substances forms tissue fluid, which is a mixture of water, hormones, oxygen, antibodies, white blood cells, digested food, salts and vitamin: Some of the leaked fluid from the blood capillaries returns to the blood at the venous end of a capillary. Some does not, and it must eventually be returned to the blood. In the tissue, there are very small blind ended vessels called lymphatic capillaries, Tissue fluid that has failed to drain into the blood capillaries drain into these lymphatic capillaries. Once it is inside the dymphatic capillaries, tissue fluid is called lymph. Importance of tissue fluid 1. It nourishes tissue cells by providing food nutrients and other important substances, 2. It removes waste products away from the cells to excretory organs. capllarycontaiing bod Figure 89. Capillary bed showing tissue fluid, lymph and blood cells sODifference between tissue fluid and blood TISSUE FLUID. No red blood cells Red blood cells Less glucose More glucose Less oxygen ~| More oxygen. Colourless Red in colour ‘More carbon dioxide Less carbon dioxide ‘No proteins-fibrinogen and prothrombin | Proteins present EXERCISE 4.5 I. _ In what ways is lymph different from tissue fluid? I In what ways is tissue fluid different from blood? IIL. In what ways is lymph different from blood? The heart Aorta Superior vena cavae Figure 40. The heart The heart is the muscular pumping organ of the blood circulatory system. Its situated between the two lungs, behind and to the left of the sternum, It is surrounded by a tough sac called pericardium. Between the pericardium and the outer part of the heart, there is pericardial fluid that reduces friction when the heart is pumping. The heart is made up of cardiac muscles. Internally, the heart has four chambers, two upper thin -walled atria (auricles) and two lower ventricles. The atria receive blood from the veins and pump it to the ventricles. The right side of the heart is completely separated from the left, the right side deals with deoxygenated blood while left with oxygenated blood. In between the right and left side, there is a special wall called septum. stThe walls of the atria are thin because they have to pump blood into the ventricle — short distance. ‘The walls of the ventricles are thick because they have to pump blood to the rest of the body ~ great distance hence more force is required. But the walls of the left ventricles are three times thicker than the right, WHY? Blood flow to the lungs is called pulmonary circulation and blood flow to the body is called systemic circulation. In between left atrium and ventricle, there is Bicuspid valve. In between the right atrium and ventricle, there is Tricuspid valve. Semi lunar valves are found at places where the pulmonary artery and aorta leave the heart. Blood flow in the heart Blood from the body tissues (oxygenated and deoxygenated) goes to the auricles of the heart via venacavae and pulmonary vein. Once it has reached the auricles, the auricle muscle walls contract forcing blood to the left ventricle and right ventricle via the bicuspid and tricuspid valves respectively. Once blood has reached the ventricles, the ventricle muscle walls start to contract, tricuspid and bicuspid valves close to prevent back flow of blood. When the ventricles are fully contracted, blood is forced to go to the lungs ~ to be oxygenated and the rest of the body tissues via aorta. This is the cardiac cycle or one heart beat. EXERCISE 4.6 1, Identify the lettered structures on the heart diagram below. 2, Identify the function played by each of following structures. a) Valve b) Septum 3. Why is the muscle of the left ventricle the most muscular within the heart? BLOOD PRESSURE Blood pressure is the force developed by the push of blood against the wallls of the vessels. It is measured by a Sphygmomanometer. When heart muscles contract, a condition called systole, pressure develops and it is called systolic pressure. 92When heart muscles relax, it is called diastole and pressure falls and it is called diastolic pressure. Blood pressure is measured as; Systolic pressure Diastolic pressure When the ventricles contract, pressure rises to 120/130 mm Hg. When the ventricles relax, pressure falls to 80/90 mm Hg. Therefore one’s normal blood pressure is normally. 120mmHg or 130 mmHg 80 mmHg 90 mmHg Figures above the normal ones are described as High blood pressure or Hypertension while the lower figures are described as Hypotension. BLOOD TYPES It was discovered, long time ago that on the cell membrane of red blood cells, there are proteins responsible for different blood groups in human beings. These proteins are called Agglutinogens or Antigens because they are responsible for Agglutination — Sticking together of red blood cells due to difference in blood groups. ‘Two types of Antigens were discovered, Antigen A and Antigen B. It was also discovered that in the plasma, there are corresponding Antibodies — Antibody-a and Antibody b, but an individual do not have a corresponding antibody to an antigen. If a person has Antigen A but not Antigen B then ho is described as Group A (he or she has antibody b in plasma). Ifa person has Antigen B not Antigon-A then is described as Group B. He has antibody-a in plasma. Ifboth antigens are present he or she is described as Group AB. (no antibody in plasma). If neither antigens are present, he or she is described as Group O (both antibodies are present in plasma). The above concept of blood groups is summarized in a table below; ANTIGEN (on | ANTIBODY (in| BLOOD ]DONATETO | RECIEVE red blood cells) _| plasma) GROUP. FROM B AAB A. Are BAB BO = AB A,B,AB,O | a,b | A,B,AB,O oO EXERCISE 4.7 1. Name the agglutinating proteins in plasma of persons with blood groups A, B, AB and o? 2, Explain why a person with blood group O is a universal donor? 53