betas 05 The Fundamental Unit of Life All organisms including plants and animals are composed of cells. Each and every cell (QTE Mut GD arises from pre-existing cell. These cells become specialised co perform different = specialised functions after division. Cell is the basic fundamental, structural and 7 OS>eYOfCOl functional unit of living organisms. In this chapter, we will study about the complex elular Composi Diferent Or structure of a cell, its various cell organelles and their functioning inside the cell. ee ere ofa Cel Discovery of Cell * Cell Organelles Robert Hooke (in 1665), examined a thin slice of cork under the primitive microscope. He observed that cork consists of smali box-like structures resembling honeycomb. He called these boxes cells. The substance called cork comes from the bark of a tree. Cell is a Latin word for ‘a little room’. Basic characteristics of cells are as follows: (9 They have the ability to replicate independently. (G#) They contain hereditary information. (iii) They can perform all the life sustaining activities on their own. (iv) They show similar chemical composition and metabolic activities. Major Landmarks Related to Cell Discovery ‘Scientist Year Work Robert Hooke 1665 Discovered cells fr frst time in cork slice with the help ofa primitive ________mcxoscope. _ Leeuwenhoek 1674 Discovered free-living cells in pond water using an improved microscope Robert Brown 1631 Discovered nucleus incall. Sehleiden and 1836-1839 Presented cell theory, which states that all plants and animals are ‘Schwann, Composed of cals and they are the basic unit of ite. Purkinje 1839 _Colned the term ‘protoplasm’ forthe fluid substance of cell Virchow 1855 Expanded the cell theory by suggesting that all calls arise trom pre-existing coll,Allnone'he Fundamental Unit of tite 103 Cellular Composition in Different Organisms On the basis of the number of cells ent i 7] they are dsified into meee ota (A) Unicellular organisms (having single cell) (ii) Multicellular organisms (having many cells) Every multicellular organism starts its life as a single cell (ce. zygote), which divides and forms many cels, All cells thus, come from pre-existing cells. The invention of magnifying lenses made the discovery of single-celled microscopic organisms possible. Differences between Unicellular and Multicellular Organisms Unicellular Organism A single coll constitutes the whole organism, ‘Mutticellular Organism Multiple cals are grouped together ina single body which ‘assume different functions in the body to for various body pars, Al cals are specialised 10 ‘perform different functions of the multicellular body so that there isa division of labour within a single cell as well as There is no division of labour in prokaryotic unicellular ‘organism, but it may be seen within the cel of eukaryotic, ‘organism, ‘group of coll. eg, Amoeba, 2.9, fungi, plants, animals ‘Chlamydomonas, including humans eto. Paramecium, bacteri Microscopes These are high resolution instruments, They are used for observing the Fine details of very minute objects. eg falls, Wit the help of a microscope, the sie of a small Sa can be magnified upto 300-1500 times. A simple tnictoscope, which is often used in schools is compound Tricroseope. 1 uses sunlight for illumination of objects fo be seen, so Its called as light microscope. = amelectron microscope 1s used to observe complex internal structures of the cel Shape and Size of Cells + Some cells have fixed shape (e.g, most plant and animal cells), while some cells like WBCs and Amoeba keep hanging their shapes. Fixed shaped cells may be of Various types like elliptical (e.g. ft cell), spherical (eg. ‘ovum), spindle-shaped (e.g. smooth muscle cell, Knobbed thread (e.g. sperm), discoidal (e.g. RBC), elongated (e.g, nerve cell), ete: Following figures depict some cells from the human body: f j K Smooth mace Gy @ sonecol 2 yh J Nerve cet Ovum Fat cell vuaon som Various cells from the human body + The size of cell varies significantly from the smallest cell of Mycoplasma (0.1-0.5 jim) 10 very large egg cells of the Ostrich (18 cm). Longest cells of human body are the nerve cells, which may reach upto a length of 90 cm. (motor neurons) Functions of Cells Each living cell has the capacity to perform some basic functions that characterise the living organisms. (i) The shape and size of cells are related to the specific function they perform. (4) Multicellular organisms like human beings perform these functions by division of labour. Different parts of human body are specialised to perform difference functions. For example, heart is made co pump blood, stomach to digest food, kidney to filter blood to make urine etc. iii) Division of labour is also seen within a single cell. Every cell possesses certain specific components known as cell organelles, These enable it to survive and perform special functions, (iv) Call organelles together along with protoplasm consticute the basic unit of life called the cell. Each kind of cell organelle performs a specific function. For ‘example, obtaining nutrition, respiration, clearing waste material or forming new progeny. Mitochondria is the organelle responsible for providing energy to the cell. Note Some cellular organelles are found in all the cells regardless of their function and the type of organism in which they are found, 1 The free-iving colls were fist observed by 2 Give name of two organisms each that are (0 Unicetuiar @ Muticetuiar 3 Name the two cells which can change their shape. ‘4 Which is the longest cel in human body? § State True or False forthe folowing statement In unicellular organisms a single cell gots specialised to perform all body functions.104 Structural Organisation of a Cell Microscopic studies revealed that every cell possesses three basic features in common, i.e. plasma membrane, nucleus and cytoplasm. Due to the presence of these features, all activities inside the cell and interaction of the cell with its environment are possible. Plasma Membrane or Cell Membrane ‘This is the outermost living, thin and delicate covering of cell. It separates the contents of the cell from its external environment. Presence of lipids (as phospholipids) and_proteins provides flexibility to plasma membrane. Itenables cell to engulf food and other materials from external environment. This process is called endocytosis, e.g. Amoeba acquires food through this process, with the help of finger-like projections called pseudopodia. Functions of Plasma Membrane (A Te allows the entry and exit of some sele materials in and oucof the cell. The cell membrane therefore, acts as semipermeable, selectively permeable, partially permeable and differentially permeable membrane. (#9 Ithelps to maintain the shape of the cell. (#i) Te acts as a mechanical barrier and protects the internal contents of the cell from leaking out. (iv) Ie provides protection against microbes and foreign substances. (») It gets modified to perform different functions, 4g. microvilli in intestine of human beings for absorption. (vi) Its semipermeability enables the cell to maint cellular homeostasis Amongst all the functions listed above, the transport of substances is the most important function. It may take place with expenditure of energy (active transport) and without the expenditure of energy (passive transport) Transport Across the Membrane Plasma membrane perform certain physical activities such as diffusion and osmosis for the intake of some substance. y Allénone Science Clo: ee These are discussed below 1. Transport Across the Membrane by Diffusion The spontaneous movement ofa substance (solid, liquid ory from a region of its higher concentration toa region ofits one concentration is called diffusion. For example, CO, (cellular waste, which needs to be e our) accumulates in higher concentration inside the cel. in ty cell’s external environment, the concentration of CO, ; lowered compared to inside of the cell. Due to this difference in the concentration, CO, moves outa the cell by the process of diffusion. Similarly, O, enters the) by the process of diffusion, when the level or concentration o O, inside the cell decreases. Diffusion is faster in the gases than in liquids and solids. Ie play an important role in gaseous exchange between the cells and also between the cell and its external environment. In addition to gascous exchange, diffusion also helps an organism in obtaining nutrition from the environment. 2. Transport Across the Membrane by Osmosis ‘The movement of water molecules through a selectively permeable membrane along the concentration gradient is called ‘osmosis. The movement of water across the plasma membrane is also affected by the amount of substance dissolved in wate. Osmosis is thus, also defined as the movement of wate molecules from a region of its higher concentration to a regiot of lower concentration through a semipermeable membrane Unicellular freshwater organisms and most plant cells tend gain water through osmosis. Absorption of water by plant roots is also an example of osmosis. The process of osmosis can be seen in a cell placed in solution of different concentrations (such as hypotonis, isotonic and hypertonic). (@ Hypotonic Solution The medium or __solutio® surrounding the cell has high water concentration # compared to inside of the cell (or the outside solution § very diluted). The cell gain water and swell up via endosmosis. Thi happens because the water molecules are free to PS through the cell membrane in both directions. Mo® water however enters the cell than that leaving it. (i) Isotonic Solution The medium surrounding a cell b# same concentration of water as that present inside cell. _ Water crosses the cell membrane in both directions, b¥ the amount moving in remains the same as the amos moving out. So, there is no overall movement of wateé- a result, no overall change is observed and the cell si remains the same. Bsllimone the Fundamental Unit of tite a_———s Gi Hypertonic Solution The medium surroundin a cell has a lower concentration of water than the ‘ell (ic. outside solution is very concentrated). Water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Asa result, the cell protoplasm gets shrinked (exosmosis). — Cell Wall Ie js a tough, non-living covering outside the plasma membrane, It is found in plant and fungal cells. Ie is feely permeable. It is mainly made up of cellulose, a complex carbohydrate that provides structural serengch o plants. functions of Cell Wall Plasmolysis (9 Cell wall permits the cells of plants, fungi and bacteria to withstand hypotonic conditions without bursting In hypotonic media, the cells tend to take up water by osmosis. The cell swells up, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell. Cell wall help plant cells to tolerate greater changes in surrounding medium. It is absent in animal cells. (ii Iehas narrow pores, called pits. Through them, fine strands of cytoplasm (or cytoplasmic bridges) called plasmodesmata are able ro cross che cll walls, Plane fells interact with each other through these cytoplasmic channels. itis the phenomenon, in which a living plant cell asses water through osmosis when kept in hypertonic solution Inthis process there is either the shrinkage oF contraction of protoplasm away from the cell wal exam 1 2 State True or False f 3 Name the process by which Cr 4 Apart from gaseous exchange, how's 5 Wich component of plant col provides Fitin the blank: molecules contribute tothe flexi the plasma membrane. fr the following statement: ye membrane. ity exhibited by Plasma membrane is a permeab! is removed from the cal, lon potent fororganime? oa 15 the structural strength to it? 105 Nucleus It is popularly called as the brain of cell. Ic is composed of a double layered covering called head nuclear membrane. It has humerous pores called nuclear pores. They transfer the materials from inside the nucleus to cytoplasm. ‘The nucleus contains chromosomes. When they arc visible as rod-shaped structures only when the cell is about to divide. It encloses a liquid ground substance called nucleoplasm. It contains nucleolus and chromatin material. Nudeolus is a more or less round structure found inside the nucleus. It does not have covering of membranes. It is known as factory of ribosomes. Chromatin is an entangled network of long, thread-like structures. It condenses to form chromosomes during cell division. Nuclear envelope (@vo membranes) Nuclopasm Nuclear pore Nuclotis 2 ceneratn nares Enooplasmic rato Eukaryotic nucleus Chromosomes contain information for the inheritance of features from parents to next generation in the form of DNA (Deoxyribonucleic Acid). Chromosomes are composed of two components, ie. DNA and protein. The DNA molecules contain information necessary for constructing and organising cells. The functional segments of DNA are. called genes. Nucleus also contains RNA that directs protein synthesis. In some organisms like bacteria, the nuclear region of the cell is poorly defined because of the absence of nuclear membrane. The nuclear region in these organisms contains only nucleic acid Such an undefined nuclear region is called nucleoid, Functions of Nucleus (#) Nucleus plays an important role in cellular reproduction. In this process, a cell divides to form two new cells. (ii) le determines the cell development and maturity by directing the chemical activities of the cell. (iii) Te helps in the transmission of hereditary traits from parents to offeprings. ies of cell. IFit is removed, (io) Ie controls all metabolic ac the protoplasm dries up.106 v Alllnone Science Class 94 ss Prokaryotic and Eukaryotic Cell Organisms whose cells lack a nuclear membrane are called prokaryotes (pro = primitive, karyore ~ karyon = nucleus). Plasma membrane Ribosomes Flagella Cellwall —Nucleoid. Fimbriae Prokaryotic cell Prokaryotes also lack cytoplasmic organelles. Most functions are thus performed by poorly developed parts, of cytoplasm. For example, the chlorophyll in photosynthetic prokaryotic bacteria is associated with membrane vesicles or lamellar structures. Plastids are not observed in it as in photosynthetic eukaryotes. The organisms with cells having a well-defined nucleus enclosed in nuclear membrane are called eukaryotes. Eukaryotic cells are further categorised into plant and animal cells, These are also different from each other in many ways. tle psa ‘memorane Golgi apparatus soph 7 Centriole Topol ‘yorome Nucor erweope a endoplasmic rehoum Mitochonction Chioroplast (b) Plant: cell Differences between Prokaryotic and Eukaryotic Celis Feature Eukaryotic cell ~ Size Generally small Generally large (110mm, (6-100 um) Nuclear region Poorly developed, Well defined, surrounded no nuclear ruclear membrane, ‘membrane and called as nucteoid. Chromosome Single More than one Nucleolus Absent Present ‘Membrane-bound Absent Present, e.g. mitochondria, cell organelles plastids, endoplasmic feticulumetc. Contriole Absent Present in animal cel Organisms Found in bacteria, Found in fungi, plants ang blue-green algae animals, etc, Cell division Takes place by Takes place by mitotic and binary fission and meiotic cell division. budding Cytoplasm ‘The large region of each cell enclosed by cell membrane is called cytoplasm. It is the fluid content present inside the plasm membrane, It contains many specialised cell organelles, each of which performs a specific function for the cell, Functions of Cytoplasm (A Ie helps in the exchange of material beeween ail organelles. (4 Ie acts as a storehouse of vital molecules such as amino acid, glucose, vitamin, iron etc. (iti) Ie acts as the site for certain metabolic pathways such glycolysis etc. Note Protoplasm ic isthe living content of a cell, It consists of the cytoplasm and nucleoplasm. rae State True or False for the following statement: The role of nuclear pores in a cell is to maintain continuity with cytoplasm, 2. What are genes? Where are they located? 3. Fillin the blank The present in nucieus directs the synthesis of cellular proteins, 4 How do prokaryotic colls reproduce? Name two prokaryotes. 5. Give one significance of cytoplasm in a eukaryotic cellAllinone The Fundamental Unit of Life Cell Organelles Large and complex cells need a lot of chemical activities to support their complicated structure and function. To keep these activities separated from each other, these cells use fnembrane-bound structures. ‘These structures perform spared functions within themselves and called cell elles. This is the main characteristic feature that iferentiates eukaryotic cells from prokaryotic cells Endoplasmic Reticulum (ER) Ieisa large network of membrane-bound tubes and sheets. It carends from outer nuclear membrane into the cytoplasm. Ielooks like long tubules round and oblong bags (vesicles). The ER membrane is similar in structure to the plasma membrane.[e occurs in three forms, i.e. cisternae, vesicles and tubules. Depending upon nature of its membrane, ER is of two types: ( Rough Endoplasmic Reticulum (RER) It contains ribosomal particles on its surfaces due to which its surface is rough. The ribosomes are the site of protein synthesis. RER is mainly formed of cisternae. (i Smooth Endoplasmic Reticulum (SER) Its surface is smooth due 10 the absence of ribosomes. Ix helps in manufacture of fat molecules or lipids. I is formed of esicles and tubules. ER appears in varying forms in ferent cells. Tc always form a network system of Nesicles and tubules and forms is cytoskeleton in cytoplasm. Functions of Endoplasmic Reticulum Ribosomes present in all active cells act as sites for (@ Ribosomes Precis, Proteins manufactured ere are protein synthesis. Pinsported throughout the cell by endoplasmic reticulum. (ii) Fat and lipid building cell mem! molecules manufactured by SER helps in ‘brane and other cell components. This process is called membrane biogenesis ii) Some other proteins and lipids synthesised by ER function as enzymes and hormones. Gx) SER plays crucial role in detosificaton of poisons and druge in iver cells of vertebrates (group of animals). (0) Ie forms a nerwork sytem, providing channel for the renapore of materials expecially proteins, Ts anspor Fananoe sarious regions ofthe cytoplasm or between the cytoplasm and the nucleus mally. Jasmic framework. Ic provide a (a fico te tl (vi) Ic gives mechanical support «© the cells. 107 Golgi Apparatus Irconsists of a scares menor | ee bound, oe Ci fluid-filled Neat Ss 2 vesicles, large 9°" spherical vacuoles s and smooth, ha é o,0°"" flattened carne These Ubrastructure of Golgi apparatus are stacked parallel ro each other. Bach of these stacks is called a cistern. The Golgi apparatus (or dictyosomes) arises from the membrane of smooth ER. Therefore, it constitutes another portion of a complex cellular membrane system. The material that is synthesised near Endoplasmic Reticulum (ER) is packaged and disparched +o various parts ofthe cell through Golgi apparatus. Functions of Golgi Apparatus (i) Golgi apparatus stores, modifies and packs products in vesicles. (ii) Iris involved in the formation of lysosomes. (ii) Ie forms complex sugars from simple sugars in some cases. (iv) Ie is involved in the synthesis of cell wall and plasma ‘membrane. Note. + The scent, who described Golg| apparatus fo the Fist time was Camilo Gog. Most of his investigations were concerned with the nervous system, His greatest work ‘was @ revolutionary method of staining individual nerve and cel structures, This method is called "black reaction’ + Ituses silver nitrate solution to trace most delicate ramification of cells. He shared the Nobel Prize in 1906 with Santiago Ramén y Cajal for their work on the structure of nervous system. Lysosomes ‘These are a kind of waste disposal system of the cell Lysosomes are membrane-bound sacs that are filled with digestive enzymes. These enzymes are made by rough endoplasmic reticulum. Lysosomes are also called the suicidal bags of a cell, During the disturbance in cellular reba or when ihe ell gs damage, biome ay rst and the enzymes can digest the absent in RBCS. eB ie HY we108 Allinone Science Class 94, ae. Functions of lysosomes ( They help to keep the cell clean by digesting any foreign material that enters the cell as well as worn out cellular organelles. Hence, called scavengers and cellular housekeepers. 1 (i) They remove foreign material by breaking small picces through its powerful ive enzymes. These enzymes can breakdown all organic materials. (iii) During starvation, the lysosomes digest stored food contents by autophagy and supply energy to the cell. Mitochondria These were first observed by Kolliker in 1880. Ic is a double membrane bounded cell organelle. The outer membrane is very porous. The inner membrane is deeply folded into finger-like projections called cristae. It creates, large surface area for ATP generating chemical reactions. ig Fibesomes DNA. molecule Imer membrane Intemal structure of mitochondria Space between outer and inner membrane is called intermembranous space. Mitochondrion is self-replicating (semiautonomous) organelle. It is the largest organelle in animal cells Functions of Mitochondria (2 Ie generates energy for various activities of cell. Ie is known as the power house of the cell. Mitochondria, ate sites of cellular respiration. They release ener; required by the cell in the form of ATP (Adenosine ‘Tuphosphate). This ATP is known as energy currency of the cell (i Whenever, the cell requires energy, ATP molecule breaks down. It generate energy to be used for metabolic activities of the body. (iii) Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Hence, they are able to make some of their own proteins, (iv) They provide intermediates for the synthesis of vatiog chemicals like fatty acids, steroids, amino acids etc, Plastids “These are found only in plant cells. The internal organisation op plastids contains numerous membrane layers embedded jn , material called the stroma. Plastids are similar to mitochonds, in external structure. They are double layered. They contain th, ‘own DNA and ribosomes. Types of Plastids Plastids are of three types ; (i Chloroplasts These are the plastids containing chlorophyll (a green pigment). They give green colour ty the plant. Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll. Ic is 4 semiautonomous organelle. Chloroplasts are also known as the kitchen of cells. Function These are important for photosynthesis in plants. Gran Starch grain Inner ‘membrane ibosomes Lametae Outer membrane Circular DNA Intemal structure of chiroplast Note Photosynthetic bacteria do not contain chloroplasts. The} contain light absorbing pigments and reaction centres, which ‘make them capable of converting light energy into chemical energy. (i#) Leucoplasts These are the white or colourless plastids They can change into other types of plastids. Function Leucoplasts store materials such as_ starch (amyloplasts), oils (elaioplasts) and protein granules (aleuroplasts) (iif) Chromoplasts. These are coloured plastids (except green). Function Chromoplasts impart colour to flowers and fruits. They are rich in carotenoid pigments and lipids. Vacuoles ‘These are the storage sacs for solid or liquid contents. In animl cells, vacuoles are small-sized, bur in plants, the vacuoles af large-sized. Some may occupy 50-90% of the total cell volum® ‘The vacuole is bounded by a membrane called tonoplast.All/nane The Fundamental Unit of Life 109 lll = _<_—X—_—_—s—X—X—as_——— functions of Vacuoles (i) Vacuoles are full of cell sap and provide turgidity and rigidity co cells in plants. ji) Many substances like amino acids, sugars, i (i) nd proteins are stored in vacuoles ss (ii) In Amoeba, consumed food items are stored in food vacuoles. (is) In some unicellular organisms, vacuoles also play an important role in expelling excess water and some wastes from the cell, Cell Division New cells are formed in an organism in order to grow, replace calls (old, dead, injured) and form gametes during sexual reproduction. Call division is a process of formation of new cells from the pre-existing cells, These are of ewo types ], Mitosis or Mitotic Cell Division This occurs for growth of organisms and to replace old, dead or injured cells. The dividing cells are called mother cells which form two identical daughter cells Each daughter cell has same chromosome number as that of mother cell “>> Ss SSB) wo dior s3/—~ Mother os with four ‘hvomosomes: 2. Meiosis or Meiotic cell division This occurs in the sex organs of sexually reproducing cells. The gametes are formed by this kind of call division. The male and female gamete unit to form zygote after fertilisation give rise co offspring, When a cell divides by meiosis, it produces four new cells instead of just ewo. The process of meiosis occurs in two stages, i.e. meiosis-1 and meiosis-l, In meiosis-1, the germ cells divide into ewo daughter cells which have only half number of chromosomes in comparison to mother getm cells, In contrast to meiosis-I, meiosis-IT resembles a normal eet fa Four daughter cals with two chromosomes: each Mosher coll with four hromosomes Gra aie 1 ident he site or protein eythesis in ace 2 whats the roleof SER i iver cols of vertebrates? 3 Which organelle constitutes the network of complex cellular rembrane system n ng cel? 4 Fitin the biank Lysosomes are Known to digest stored food during stamation tivough process called 5 Comment oa the similaty between mitochondha and pasts? ny 0. 6 Name the organelle, which acts as storage sacs ofthe cel To Study NCERT Activities Visit hitps://goo.gl/aAyGhm OR_ Scan the Code fgpy Intext Questions 5 How is a prokaryotic cell different from ; a 1 Who discovered cells and how? Pg59 eukaryote c9ll?, Pass Sol. Cells were discovered by Robert Hooke in 1665. or pla obieere elle invesoork ses waite het ot Fill in the gaps in the following table illustrat Primitive mictoseqpe The cork dice resembled the ng Structure of a honeycomb consisting of many small differences between prokaryotic and eukaryotic compartments or box like structures. Hooke called cells. Pe6s these boxes as els. Sol 2 Why is the cell called the structural and Prokaryotic Cell Eukaryotic Celt functional unit of life? a ‘Sze: generally small, Size : goneraly large as (-10um) twm=10-%m (S-100uR Sol. Afl liding organisms are made up of cells, which RE A tee perform various functions essential for survival of Nuclear region: poorly Nuclear region: well-defined the organisms, eg. respiration, digestion, defined ending pe, erclaurourded ia ane ‘excretion etc. Thus, call is the functional unit of Living cells are capable of performing certain bac inside the cell from outside. functions due to the presence of cel organelles present "TRE srdeer moves Ua and out of, citjcell by che ic. these are destroyed then cell will not be able to wort process of osmosis. Osmosis is the diffusion of properly and will die after sometime. ‘water from a region of its high concentration to 8 Whyareh lysosomes known as suicidal bags? lon oes through a semipermeable | a Sol Lysosomes contain powerful digestive enzymes. Durisg 4 Why is the plasma membrane called a the disturbance in cellular metabolism, lysosomes mf selectively permeable membrane? Pg61 burst and digest their own cell, Therefore, they are Sol The plasma membrane is elle, a selectively ° etna permeable membrane because it allows entry and Where are proteins synthesised inside the cell? ‘exit of some selected molecules only through the proven sy Pg6 cals. It also. prevents movement of some other materials. Sol. Ribosomes are the site of protein synthesis inside the celllinone The Fundamental Unit of Life m oe gxercises (On Pages 66 and 67) Make @ comparison and write down ways, in which plant cells are different from animal cells Comparison of Plant Cell and Animal Cell Plant Cell Cel walls present outside the plasma membrane Generally regular in shape Lager in size than animal cells, Sol. Animal Cell Cel wall is absent. Generally ireguiar in shape, ‘Smaller in size than plant cols, Plastds are present Piastids are absent in all ‘except Euglena, permanent and large vacuole is Vacuotes are many, small present and temporary. Many simple units of Golg apparatus called dictlyosome are present A single, highly complex and prominent Golgi ‘apparatus is present 2. What would happen if the plasma membrane ruptures or breaks down? sol, In case plasma membrane ruptures or breaks down, (i) all the useful substances will move out of the cell because membrane is selectively permeable (i) the transportation of materials wil be disturbed (ii) the cell wil loose its normal shape (io) shis may lead ultimately co the death of the el. 3. What would happen to the life of a cell if there was no Golgi apparatus? Effects of the absence of Golgi apparatus on life ofa cell areas Te ferent types of (9 The packaging gee imide ose he cll be influenced (ii) ‘The products of cell cannot be stored and modified later. Sol. Ui) This will affece the lysosomes formation. This will cause cei laion of worn out and dea ell organelles within the cell, which may cause cell death, 14 Which organelle is known as the powerhouse of the cell? Why? Sol, Mitochondria are oxidative enzymes, which ee ise the food and convert it ‘energy currency ‘of the cell in the form of ATP (Adenosine Tsp) Tn or unk the chemical compo aed powethoue of eal 5 Where do the lipids and proteins constituting the cell ‘membrane get synthesised? sa The he of Hah asi mee Resim (SER) TM ined 0 the Rough Enfoplic Reticulum (RER)- 6 How does Amoeba obtain its food? Sol, Amoeba obtains its food through endocytosis. Ie isthe process of ingestion of food through che plasma membrane. This occurs due to flexibility of plasma membrane, which enables the Amoeba to engulf food and other materials From surroundings. 7, What is osmosis? Osmosis isa process of diffusion of water from a region Sol ofits higher concentation to a region of lower concentration through a semipermeable membrane. 'g Carry out the following osmosis experiment: Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now, (i) keep cup A empty (i. putone tea spoon sugar in cup B. (ii) putone tea spoon saltin cup C. (iv) put one tea spoon sugar in the boiled potato cup D. Keep them for two hours. Then observe the four potato cups and answer the following: () Explain, why water gathers in the hollowed portion of B aid C? (id) Why is potato A necessary for experiment? (ii) Explain, why water does not gather in the hollowed out portion of A and D? (8 The water gathers in the hollowed portion of B and C due © the process of osmosis, Concentration of soluce (sugar in cup Band sal in cup C)is higher inside the cup than water. Hence, water flows fiom a region of its. higher concentration (0 the region of lower (i Potato A acts as reference of control for the experiment, which helps in comparing results. (iii) Water does not gather in the hollow portion of A and D because ofthe following reasons: (a) Hollow portion of potato 4 is empry and there iso concenttaiondifeence so, no osmois (b) The hollowed portion of potato D contains sugar, but the potato cup is boiled. Osmosi cannot occur as semipermeable membrane is destroyed by boiling. 9. Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes. The mitotic cell division is required for growth and repair of the body. The meiotic cell division is invol in the Formation of gametes. vote Sol. Sol.SUMMARY Collis the basic structural and functional unit of all living organisms. It was discovered by Robert Hooke in the year 166s. Unicellular organisms are those organisms which are made up of a single cell only, e.g. Amoeba, Chlamydomonas, bacteria, et, Multicellular organisms are organisms made up of many cells. Those cells group together and assume different functions in the body to form various body parts, eg. plants and animals. = Prokaryotic cells are cells lacking a well-defined nucleus enclosed by nuclear membrane, e.g. bacteria and cyanobacteria ‘* Eukaryotic cells are those having a well-defined nucleus enclosed in nuclear membrane, e.g. plant cell and animal cell. * Plant cells possess a cll wall and a vacuole that occupies most of the space. It lacks centrosome and centrioles. = Animal cells do not have cell wall, these possess highly complex Golgi bodies, centrfoles, et * Structurally, a cell mainly consists of plasma membrane, cytoplasm and nucleus. Cell organelles such as Golgi bodies, mitochonéy, ‘tc, are also present in cytoplasm, * Plasma membrane js the outermost covering ofthe cell that is composed of proteins and lipids. It permits the entry and exit of sone materials. It maintains the shape ofthe coll, acts as mechanical bartier and protects the internal contents of cel. ‘+ Transport of substances across plasma membrane may take place by diffusion, i.e. process of movement of solutes or osmosis, ig process of movement of water * Nucleus is properly called as brain ofthe cells It controls all functions ofa cell. It also determines the development of cell by directing the chemical activities of cell * Cytoplasm is the fluid content present inside the plasma membrane that contains many specialised cell organelles and acts as ast for metabolic pathways such as glycolysis, + Endoplasmic reticulum isa large network of membrane bound tubules and sheets. I plays an important role in protein and lipid synthesis. * Mitochondria is known as the powerhouse of cell that releases energy required by the cel in the form of ATP. + Golgi apparatus consists of a system of membrane-bound vesicles called cisternae. It helps in the formation of lysosomes and in storing and packaging of various molecules in a cell + Lysosomes are waste disposal system ofa cel also called as suicidal bags of cell. * Plastids are found in plant cells as chloroplasts, chromoplasts and leucoplasts. Vacuoles are storage sacs of solids and liquids * Cell division The process by which coll increase in their number is called ce division. It is of two types * Mitotic cell division Tt occurs in somatic cells of body for growth and for repairing of old/injured cells. The chromosomes nurabesis the newly formed cells remain same as in mother or dividing cell. * Meiotic cell division 1! occurs germ cells of sexually reproducing organisms to form male gameles and female gametes, These have halps number of chromosomes as compared to mother cell For Mind Map wi Visithttps://goo.gV/U3NXJ2 OR §ean the CodeObjective Type Questions When movement of the solvent takes place from outside to inside the cell (inward movement) the process is endosmosis. Ic occurs in hypotonic solution and causes the swelling of cell. Hypotonic Vacuole Multiple Choice Questions 1 The term ‘protoplasm’ was coined by {@) Purkinje (0) Robert Hooke () Virchow (€) Robert Brown ol, (2) Purkinje in 1839 coined the term ‘protoplasm’ for the fluid substance of che cell. 2 Choose the incorrect statement from the following options {a) All cells arise from pre-existing cells only (0) Rudolf Virchow proposed the cell theory () Nucleus was discovered by Robert Brown in 1831 (@) The nucleus and cytoplasm of a living cell, altogether form the protoplasm Sol. (b) The cell theory was proposed by Schleiden and Schwann in 1839, postulating that all living beings are composed of cells and cheir products. In 1855, Rudolf Virchow modified the cell theory with his ulate, ‘Omnis cellula--cellula, which means, a new cell is derived from a pre-existing cell only. 3 The flexibility of plasma membrane can be contributed to the presence of (@) proteins (b) lipids (c) nucleic acids (@) Both (a) and (b) Sol. (d) Presence of lipids and proteins as phosph« provides flexibility to plasma membrane. This helps ell in engulfing food and other materials from ‘external environment. 4 Acell will swell up if the {a) concentration of water molecules in the cell fs higher than the concentration of water molecules in surrounding medium (0) concentration of water molecules in surrounding medium is higher than Concentration of water molecules in the cell (c) concentration of water molecules is same in the cell and in the surrounding medinmtration of water molecules does not rncentration of wat cl ae CERT Exemplar (6) Osmosis isa spontaneous process where Othigher is concentration ro region af lower solute Concentration through a selectively permetbie Seembrane,soas to tend ro equaliseits concentration fn the both two sides in a biological system. Sol. Sol. Sol. Sol. HO, Tugid The cell wall of which out of these is not made up of cellulose? (a) Bacteria (b) Hyarritla (c) Mango tree (a) Cactus ‘CERT Exemplar () Plant cells, in addition to the plasma membrane, have another rigid outer covering called the cell wal. Bacteria is noc a plane therefore, its cell wall is made up ofa heteropolysaecharide named peptidoglycan. Which one of the following terms describes ‘anucleus without nuclear membrane’? (a) Nucleotus (0) Primitive nucleus {c) Nucleoid (q) All of these (0 The primitive type of undeveloped nucleus which lacks a nuclear membrane is called nucleo ‘A nucleoid is found in prokaryotic cel, e.g. bacteria, mycoplasma. Which one of the following cellular functions is performed by endoplasmic reticulum ? (@) Production of hydrolytic enzymes (0) Supply of energy to cell (c) Formation of lysosomes (a) Production of vacuoles () The digestive o hydrolytic enzymes (proteins) are produced by rough endoplasmic reticulum for the synthesis of lysosomes. Organelle other than nucleus, containing DNAis {) endoplasmic reticulum (0) Golgi apparatus (c) mitochondria (@) lysosome NCERT Exemplar (0 Other chan nucleus, mitochondria contain DNA and are able o synthesise their own proteins. They ate regarded as semiautonomous organelles.14 All nonescience Class 9 S————————_—?::90., SSS, 9 Kitchen of the cell is (a) mitochondria (c) chloroplast (a) Golgi apparatus NCERT Exemplar Sol.(0 Chloroplasts have a green’ pigment called chlorophyll and they are involved in the photosynthesis offood. Therefore, they are also known, chen of the cc (b) endoplasmic reticulum as the 10 Select the correct functional role of vacuole ina cell. (a) Vacuoles do not help in maintaining rigidity of cell (0) Vacuoles form thread-like tail in sperms of ‘many mammals (c) Vacuoles expell excess water and waste products from the cell (4) Vacuoles store only excretory products of a cell Sol. (2) In unicellular organisms, vacuoles carry out the role of expelling excess water (osmoregulation) and wastes from the cell (excretion), They also store food and. water in cell and help in maintaining rigidity of cell by controlling osmosis. Vat root tip, the number of divisions to produce 100 cell would be fa) 25 (b) 50 (c) 99 (a) 100 Sol. (6) The cells of root tip divide by mitotic cell divisions so ro make 100 cell, $0 divisions in 50 mother cells will take place. ‘This way che roo ip will keep growing are ovary daughter cell will again divide to form new cells. 12 The meiotic cell division in plants occurs in (a) leaves and stem —_(b) stem and branches {c) in anther and ovary (a) None of the above Sol. (d) The meiotic cell division occurs in anthers and ‘ovary co form pollen grain (male gamete) and egg cell female gamete. Fill in the Blanks 13.An additional protective layer in plants present outside the plasma membrane is called Sol: cell wall 14 The cell theory was refined by ...... Sol. Virchow 15The cell organelle involved in cellular respiration is... Sol. Mitochondria 16 Ribosomes are concerned with the synthesis OF esse Sol. proteins True or False T7Plant cell vacuoles occupies 10-20%, plant cell volume. Sol. False; Plant cell vacuoles occupy more than 10-293 plane cell volume. 18Chromosones is _ condensed chromation Sol. True, 19 Oxidation of mitochondria. Sol. True form. 9 food takes place i 20 All kinds of plastids have pigments. Sol. False; Leucoplast isa kind of plastid that do not ha pigments Match the Columns 21 Match the following columns. Column 1 Column A. Robert Hooke _()_Discovery of nucleus B. Schleiden and (i) Protoplasm Schwann C. Robert Brown Cell theory i D. Purkinje (iv) Discovered cat Sol. A-M(iv), B->(iii), C9), DG) Assertion-Reason Direction (Q.Nos. 22-26) In each of she fallowing questions, a statement of Assertion is given by th corresponding statement of Reason. Of the statements, mark the correct answer as (a) If both Assertion and Reason are true and Reaso® is the correct explanation of Assertion (0) Itboth Assertion and Reason are true, but Reasoo is not the correct explanation of Assertion {c) If Assertion is true, but Reason is false (d) If Assertion is false, but Reason is true 22 Assertion Rudolf Virchow proposed cell theory. Reason His cell theory states that all plants and animals are composed of cells. Sol. (6) ‘All plants and animals are composed of cells’ wa presented as cell theory by Schleiden and Schwan? (1838-39). Rudolf Virchow modified and expand this earlier theory by suggesting that ‘all cells ai from pre-existing cells’.The Fundamental Unit of Life 93 Assertion Chromosomes are constituted by DNAand protein, Reason These are thread-like structures present in nucleus, Sol. (8) Chromosomes are made up of DNA and. proteins (ue. histones). These are thread- like seructures present in nucleus of the cell and contain genetic information that is transferred from parents to next generation, 24 Assertion Prokaryotic cells are primitive and larger than eukaryotic cells. Reason Prokaryotic cells lack cytoplasmic organelles. Sol. (d) Prokaryotic cells are smaller in size as compared to cukaryotic cells. These cells also lack cytoplasmic membrane bound organelles. Thus, most functions are performed by poorly developed parts of cytoplasm. 25 Assertion Golgi bodies store, modify and pack products in vesicles, Reason They are involved in the formation of lysosomes, Sol. (6) Golgi bodies store, modify and pack products (proteins) in vesicles, which ate distributed to various parts of the cell. These Golgi are also involved in the formation of lysosomes (waste disposal system of the cell) 26 Assertion Mitochondria are known as the powerhouse of a cell. Reason These generate energy (as ATP) for various cellular activities. Sol, (a) Mitochondria are the sites of ‘cellular respiration. These generate energy required by the fallin the form of ATP which gets utilised in ‘Callular functions. That is why mitochondria are also known as power house ofthe cell. Case Based Questions Direction (Q.Nos. 27-30) Answer the questions on basis of your understanding of the, following passage and related studied concepts: Thecytoplasm isthe liquid part of the cell. Ie contains Several simple and complex materials of the following clements, Study the table given and answer the ‘westions, 27 Which amongst the following is not a trace element? (a) Calcium: (b) Chloride (0 todine (a) Carbon Sol. Carbon 28 Cytoplasm acts as the site of metabolic pathways like (a) Glycolysis (0) Ultraiteration (c) Photolysis {@) None of these Sol. Glycoljsis is a metabolic reaction that occurs in cytoplasm of cel. 29 Is cytoplasm living content of the cell? Sol Yes, Gyroplasm i living content ofthe cell. 30 What will happen if the cytoplasm of a cell is removed ? Sol. In the absence of cytoplasm there would only be nucleus, so cell wor’ be able to perform its functions at all Direction (Q.Nos. 31-34) Answer the questions on the basis of your understanding of whe following passage and related studied concepts: To keep metabolic activities of different types separate from each other, eukaryotic cells have membrane bound “organelles within themselves. Cell organelles are “small organs” of the cell and are found embedded in the cytosol. They form living part of the cell. Each of them has a definite shape, structure and function. Examples of such organelles are nucleus, mitochondria, chloroplasts, endoplasmic reticulum, 31 Name the organisms in which plasma membrane and cell wall both are found. Sol. Plant cell/Plant 32 State the function of ribosomes. Sol. These are the site for protein synthesis.33 Much of the DNA is localised in chromosomes of the nucleus. What is the other major constituent of the chromosomes? Sol. Apart from DNA, the other major constituent of chromosomes are proteins (basic in nature). 34 Which of the following organelle in a eukaryotic cell is concerned with synthesis and transport of lipid molecules within a cell? Sol. Lipid molecules are synthesised and transported within «cell by smooth endoplasmic reticulum, Very Short Answer Type Questions 35 Name two unicellular organisms. Sol, Paramecium and Chlamydomonas are the two unicellular organisms of the kingdom-Protozoa and kingdom plantae, respectively 36 Name the process in which diffusion takes place through a semipermeable membrane. Sol. Osmosis takes place through a semipermeable membrane, 37 What will happen if the already swollen raisin is kept in salt solution? Sol, ‘The water flows out from the raisin and gocs into the solution medium. Consequently, che raisin shrinks in 38 Name the process by which unicellular freshwater organisms and most plant cells tend to gain water. Sot. Endosmosis, i. inward movement of water into the cell from surrounding medium. 39 What is the function of cellulose in plant cell? Sol. The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance, which provides structural strength to plants. 40 Why is nucleus called controller or brain of the cell? Sol, The nucleus coordinates and directs all the metabolic functions ofthe cell, hac is why itis called controller or brain of the cel 41 State two important functions of the nucleus of the cell, Sol. (i) Nucleusis the control centre of a cel. (Te ebnsists of cell's DNA (genetic information) in the form of genes which carries hereditary characters from one generation to another. 42 What is DNA? Where is it present? Sol. DNA is Deoxyribonucleic Acid. It is the genetic map of | an organism, present in nucleus, Alli;ane Science Classy, re 43 How DNA is present ina cell which is () dividing? (i) ‘not dividinge Sol. ( Chromosomes (i) Part of chromatin material 44 Which organelle is called factory y ribosomes? Sol. Nucleolus is called factory of ribosomes. 45 What are dictyosomes? Sol. In plants, Golgi bodies are called as dietyosomes, 46 Is there any animal cell that lacks lysosomes? Sol. Mammalian RBCs (Red Blood Corpuscles) lag lysosomes, 47 In which cell organelle, the complete breakdown of glucose in the presence g oxygen takes place? Sol. The complete breakdown of glucose in the presena of oxygen in a cell is called aerobic respiration. takes place in mitochondria. 48 Name the energy currency of cell. Sol. Adenosine Triphosphate (ATP) is considered by biologists to be the energy currency of eel 49 Which organelles are present only in planis cells and possess their own genome ani ribosomes? Sol, Plastids ate found in plant cells only and conti DNA, RNA and ribosomes. 50 Name two structures, which are found in plant cell, but not in animal cell. Sol. Chloroplast and cell wall are found in plant cel, bu not in animal cel 51 Name the type of plastid that helps in the process of photosynthesis. Sol, Chloroplast helps in the process of photosynthet 52 Plant cells have large vacuoles eat surrounded by a membrane. What is th name of this membrane? Sol, The membrane that surrounds the vacuole is cll ‘tonoplast, 53 Mitotic cell division can be observed which part of the organisms? Sol. Tt occurs in somatic cells of the body of organism’ 54 How are gametes formed in sexual reproducing organisms? Sol. Gametes are formed by meioic cell division | sexually reproducing organisms,eT allinone The Fundamental Unit of Life 17 eee SSS SSS Short Answer (SA) Type Questions 1 List the contributions of the scientists given pelow in context of the study of cells (i Antony van Leeuwenhoek (ii) Robert Brown (iii) Camillo Golgi Sol. (@ Antony van Leeuwenhoek discovered free-living calls in pondwater using an improved version of microscope (ii Robert Brown discovered the brain of the cell, i. nucleus, which controls all the physiological activities of cell. ii) Golgi bodies were discovered by Camillo Golgi using a weak solution of silver nitrate to stain individual nerve and cell structures. 2 What are the consequences of the following conditions? NCERT Exemplar () Cell having higher water concentration (ii) Acell having lower water concentration (iii) A cell having equal concentration to ‘its Sol. (i) A cell having higher water concentration than will lose water. (id) A cell having lower water concentra ‘surrounding medium will undergo ‘endosmosis and absorb water from outside, Ca cll shaving il neler gain nore ‘water to the external medium. ion chan 3 State in brief, what happens when () Dry apricots are left for some time in pure water and later transferred to sugar solution, (i) Rheo leaves are boiled i and then a drop of sugar syrup is in water first pour onit. ii) Golgi apparatus are removed from the ae NCERT Exemplar Sol. (Dry apricots will swell up duc eo endosmosis Oona in pure water On being eansfered to sugar solution, they shrink due co exosmosis. (ii) Calls of Rhoe leaves ate killed due o boiling, they will not undergo plasmolysis ii) Formation oflysosome and secretory vesicles will op and biosynthesis of proteins and lip will not occur. 4 (i) Explain how do cell walls permit the cells of fungi to withstand very dilute external media without bursting. (ii) Why does the skin of your fingers shrink when you wash clothes for a long time? NCERT Exemplar Sol. (i) Fungi withstand very dilute/hypotonic external media without bursting because of their cell walls In such media, the cells swell up by taking tp water through osmosis and hence, building up pressure aginst the cell wall. The wall exer an Qfual_presure against the swollen cell, thus preventing it from bursting. (i The solution of soaps and detergents are hypertonic as compared co the osm concentration of our skin “Therefore, washing of clothes results in exo skin cells that come in contact with the. soap Solution. Due to this reason, the skin of the fingers Shiinks while washing clothes For a long time. 5 Describe the structural features of cell membrane and cell wall. Why is cell membrane called selectively permeable membrane? Sol. Cell membrane is flexible, semipermeable and living portion of cell, which is made up of lipids and proteins. On the other hand, cell wal is tough, rigid dnd non-living portion of plant cell, which is made up of cellulose. "The plasma or cell membrane permits the entry and exit of selected materials in and out of the cel. Ir also prevents the movement of cell content outside the Eell. Hence, it is called sclectively permeable membrane. 6 Explain in detail what do you know about the structure of nucleus. Sol. Robert Brown discovered nucleus in the cell in 1831. The nucleus is the control centre of a cel. Structure of nucleus is composed of: (A Nuclear membrane It encloses the nucleus in eukaryotes. The nuclear membrane is penetrated by large nuclear pore complexes, which selectively transport molecules into or out ofthe nucleus. i) Nucleoplasm Ic isa kind of protoplasm found in the nucleus containing genetic material (DNA), chromosomes and nucleolus, i) Chromatin ‘The chromatin material inside the nucleus is an organisation of DNA and prot AAs a cell prepares itself to divide, the chromatin condenses and becomes thick enough to form specialised structures called chromosomes.8 Allynone science Class 94, —————————————_—_—_—_—_—__— (ia) Nucleolus It acts as the most important site of RNA synthesis. It was first recognised by Fontana in 1874, 7 (i) Where are chromosomes located? What is chromatin material and how does it change just before the cell divides? (i) ‘The functional segments of DNA are genes.’ Give reason. Sol. (i) Chromosomes are located in the nucleus of the cells. Chromatin is a mass of thread-like structures. It condenses to form chromosomes just before the cell divides. (i) Genes present on DNA segments carry the hereditary information in them, which is transferred from one generation to next. They determine the structural and functional aspects of next generation 8 State three differences between plasma membrane and cell wall. Sol. Plasma Membra Coll Wall Tpodes suppor and ghesstengh ard shape tothe ca rset oe lat cel This semipermeable in nature itis completely ‘allowing the entry of selected permeable in nature. molecules into the cell. itis elastic, lving and thin itis nid, non-lving and thick 9 What do you mean by the following terms? (i Protoplasm ——_(ii)_Cytoplasm (ii) Nucleoplasm Sol. (i) Protoplasm It is the living substance present in the cell containing both cytoplasm and nucleoplasm. (i) Cytoplasm It is2 part of protoplasm filled within the space between the nuclear membrane and cell membrane. It is homogeneous in nature containing water, amino acids, oxygen etc. (ii) Nucleoplasm Ie isa cransparent, semi-fluid substance filled within the space between nuclear ‘membrane and nucleolus. It consists of nucleic acids, basic and acidic proteins, lipids and minerals. 10 State some differences between cytoplasm and nucleoplasm. Sol. Differences between cytoplasm and nucleoplasm are as follows: Cytoplasm ‘Nucleoplasm “THis enclosed by plasma Itis enclosed by nuclear membrane, membrane. (Cytoplasm contains the It contains nucleolus, ~ ‘organelles, vitamins, chromosomes etc.” enzymes, sugars ete als Genera ses ORR GI Gasie Itis general mass of {tis semi-fuid ground protoplasm excluding substance found in ucleus, ucleus, 11 Differentiate between Rough Endoplasme Reticulum (RER) and Smooth Endoplasmic Reticulum (SER). How endoplasmic reticulum is important for membrane biosynthesis? Sol. Differences between RER and SER areas follows “Rough Endoplasmic Smooth Endoplasmic Reticulum (REF) Reticulum (SER) In ER, rbosomes are ‘IN SER, ribosomes arent “attached o the surlace. attached tothe surface Ithelps in protein synthesis. It helps in lipid synthesis itis formed of tubules and is _Itis formed of cisternae situated near the nucleus. ands situated near the plasma membrane, Importance of ER in membrane biosynthesis areas follows: (9 RER synthesises proteins, which are passed onto Golgi apparatus. (ii) The SER helps in the manufacturing of fats and lipids, which along with protein help in building of cell membrane. (ii) Ic also helps in cransporting proteins to vatiow places. 12 Describe the phenomenon of membrane biogenesis. Give one function of ER. Sol. The smooth endoplasmic reticulum helps in the manufacture of lipid or fac molecules, important for cell function. Some of these lipids and proteins manufactured in RER help in building the ol membrane. This process is known as membrane biogenesis. ER functions as a cytoplasmic framework providing surface for some of the biochemical activities of th calls 13 Name the organelle of the cell, which & involved in the formation of lysosomes. Write its functions in the cell. Golgi apparatus is the organelle involved in the formation of lysosomes. Functions of Golgi apparatus are: (A. Storage, modification and packaging of product in vesicles. (i) Helps ro make complex sugars from simple sug Sol. ee‘all/wone The Fundamental Unit of ite (i) Material synthesised near the ER is packaged and dispatched o various argets inside and out the cell through Golgi apparatus. 14 Name the organelle of the cell, which has membrane-bound sac filled with powerful digestive enzymes. Write any four common functions it performs inside the cell. Sol. Lysosome is membrane-bound sac filled with powerful digestive enzymes. For functions of lysosomes, refer to Pg 118. 15 (i) Why lysosomes are known as ‘scavengers of the cell’? NCERT Exemplar (ii) Lysosomes are self-destructive, True/ false. Give reason, Sol. (3 Lysosomes are called scavengers of the cell because they remove dead and worn out cells by digesting them apd acta kind of wate disposal puem of (2) Lysosomes are self-destructive. Thisis true as during breakdown of cell structure, lysosomes may busst and the enzymes contained in it may eat up their own cells. 16 How many membranes are present in mitochondria? Give _ the _ characteristic features of these membranes. What is the advantage of such features? Sol. Mitochondria have two plasma-membranes. ‘The outer membrane is very porous, while the inner ‘membrane is deeply folded and is selectively permeable) Porous membrane helps in getting oxygen and food, Aiile the folds create a large surface area for ATP generating chemical reactions. 17 Name a cell organelle found only in a plant cell and mention its various types along with their functions and location. 18 Give the —_ differences Jeucoplasts and chromoplasts. Sol. Refer to solution of Q 17. between 19 Which type of plastid stores starch, oil and proteins? Sol. Leucoplass are che plastids that function to store starch, oil and proteins and hence, i is of three types (9 Amyloplasts Store starch (ii) Blaioplats— Store oil (ii, Aleuroplasts~Store proteins 20 Write the name of different plant parts in. which chloroplast, chromoplast and Jeucoplast are present. NCERT Exemplar Sol. Refer to solution of Q. 17. 21. Why does plant cell possess large-sized vacuoles? Sol. Plant cell possesses large-sized vacuole because (0 it sores sale, sugat, amino acid organic acid and some proteins (i the vacuole contains cell sap and helps in maintaining turgiity of cell. (ii they store some metabolic byproducts or end products of plant metabolism. {iv) lysosomal enzymes occur in vacuole of plant cell 22 State reason for the following: (i) Mitochondria is known as powerhouse of the cell. (i) Plastids are able to make their own protein. (iii) Plant cell shrinks when kept in hypertonic solution. 19 aS Sol. Plastds are found only in plane cells. Sol. (9 Oxidation of food takes place in Tope of lass ate: mitochondria, that result in the release of YP energy in the form of ATP. This energy helps fame of ie Pigment Function Location in various chemical activities needed fr life. plastid present Hence, mitochondria is known as THlroplast Green (called Invoed inthe. Lesves rarieaef need ow cehiorophyl)_ phesoey (ii) Plastids have their own DNA and ribosomes. 3 ‘Therefore, they are able to make their own alractve coloured parts e y onl and tuts. (Gi) Hypertonic solution has lower concentration ‘No pigment Stores starch, ‘Underground! eh ‘water than the cell. When a plant cell is Tonzopiast NO pgmeN Straten sora pars pein i, waier present in the cell leaves the (colour oe of plant cell due to exosmosis. Therefore, cll shrinks.120 » Allsnane Science Class 94, ——— ——— 23 Name the organelles, which show analogy written as under. (i) Transporting channels of the cell. (ii) Powerhouse of the cell. iif) Packaging and dispatching unit of the cell. (iv) Digestive bag of cell () Storage sac of the cell. (vi) Control room of the cell. NCERT Exemplar Sel. (@ Endoplasmic reticulum (i) Mitochondria (i) Golgi appararus () Vacuole (i) Lysosome (ei) Nucleus 24 Enlist any three functions of vacuoles. Sol. The three functions of vacuoles are as follows ( Vacuotes are fall of cell soap and provide eurgidity and rigidity to cells in plants. (i) Many substances like amino acids, sugars, organic acids and proteins are stored in vacuoles. (a In Amorb, consumed food items are stored in ood 25 Differentiate between the mitosis ang meiosis. Sol. The difference between mitosis and meiosis tabulated below 7 a Mitosis Meiosis It occurs in germ cole g the body of organisms, occurs in somatic coalls of body of the organisms. Two daughter calls Four daughter cals ae are formed, formed. The number of The number of chromosome remains chromosomes is reduced same in daughter to half in daughter cel cells as found in comparison to mother mother cel calls. Its helpful in growth, Itis helpful in sexual repair of body of "reproduction by forming organisms, male and female gametes, Long Answer (LA) Type Questions 1 Describe an activity to demonstrate endosmosis and exosmosis. Draw the diagram also. Sol. Activity to show endosmosis and exosmosis Put dried raisins in plain water and leave them for some time. Then place them into a concentrated solution of salt. vraige Alter sore (eae es,“ eens @ raisins "ty page ae EES Concentrated Shrunken mee sa Sol, Observation (@ When dried raisins are placed in plain wats raisins swell up due to osmotic entry of watt into raisins. Plain water is hypotonic medium for raisins. Thus, endosmosis occurs. (4 When swollen raisins are transferred t0 2 concentrated solution, raisins shi Concentrated solution is a hypertonic medium for swollen raisins. Thus, exosmosis occuts Explain main functional regions of a cell with the help of a diagram Plasma membrane, cytoplasm and nucleus are thee® ‘main functional regions ofa cell. ( Plasma membrane It is a thin, selectivdy permeable membrane, covering the cell and i made up of lipids and proteins.= ‘Allinane The Fundamental Unit of life 121 (G9 Cytoplasm cis aqueous material containing a sai of cll oganls along with noniving (ii) Nucleus Ie is che control centre of a cell, It contains the cell hereditary information (DNA). Cel membrane Goi apparatus Secretory Ribosome granules Rough endoplasmic retculum Nusleous Nuciear membcane Nuseoplasm Smooth 4 jtopasm ‘endoplasmic a} cenitosame reticulum Mitochonrion Uysosome A eukaryotic cell 3 Given below statements have underlined words which may be incorrect. Rewrite these words and state one function for each. oi them other than tho 8) given (i) The fundamental organisational unit of (ii) The cell wall is an active part of the cell, iy The. presence of planma_membrane liv) The Golgi body functions both as a “ their primary function is to provide Sol. () A Cell They perform many important A tact Tndcons in Twig pass eel He iy Mama, membrane © Rte eens thea (ii) Cell wall. Te helps in interaction among plop Ci al epic hanes Se ceeeccnees ah Ir functions as (o) Eade arma prog re St Sela Aettamicertecel oats Thy mpatcslure beprscl caer ower nd a Ie acts as a mechanical age of cellular 4 (i) Draw a neat labelled diagram of animal cell. (ii) Name the structure, which helps in (a) energy production (b) exchange of materials cytoplasm and nucleoplasm, (c) lipid synthesis between Sol. (i) For the diagram of an animal cell. Refer to the fig. ‘on Pg 106. (i (@) Micockondtia (6) Nuclear pore (0 Smooth endoplasmic reticulum 5 Why are mitochondria called powerhouse of the cell? Give three similarities and one difference between mitochondria and plastid. Sol. Mitochondria are often associated with cellular respiration and energy generation of the cell. ‘The energy requited for various chemical activites is telewed By the mitochondria in the form of ATP molecules. For this reason, mitochondria are known as the powerhouse ofthe cell ‘Thace similarities berween mitochondria and plastids are as follows: (A. Both have their own DNA and (i) Eternal structures of mitochondria and plastids are i. Both have more chan one membrane layer. (One major difference beeween mitochondria and plastids is thac mitochondria are present in both plane and animal cells, whereas plastids are present only in plane cells 6 Write the main functions of atleast ten cell components. Sol. (j) Plasma membrane It acts as a semipermeable ‘membrane and allows only selective substances co passthrough i (i Chromosomes ‘To carry hereditary characters of an organism fiom one generation to another. (i, Lysosomes Breakdown of unwanted ‘mactomolecules is the main function ofthese organelles, i») Ribosomes These help in protein synthesis, (®) Nucleus Control centre of the cell. Contains cellular DNA (genetic information) in the form of genes tochondra ‘The main function of micochondtia. in acrobic cells is the production of energy by synthesis of AT a (vid) Nucleolus Biosynthesis of ribosomal RNA (FRINA) and acts asa platform for protein synthesis, (wa122 Allznane Science Class 9) ——>>>>=>=>=>=EE>E=E=————————————_ (i) Chloroplasts are green-coloured plastids whi (vii) Cell wall _Ieprovides protection and rigidity o the plant cell. (és) Chloroplasts These are the sites of photosynthesis within plant cells. (x) Endoplasmic reticulum Serves as channels for transport of materials. 7. Grass looks green, papaya appears yellow. Which cell organelle is responsible for this? CBSE 2016 contain green coloured pigment thlorophyl aa « Gif) Genes ate the functional segments of Dyy (present on DNA) which control a specific trait making specific protein. q 9 (i) Describe the role played by the lysosomes. Why are they termed ay suicidal bags? How do they perform the function? Sol, Plastds These are found in plane cells only, Plats are (i) What happens to the dry raisins, when the major cell organelles in plants, On the basis of placed in plain water for some time? Stae Pigments present in plastids, they are divided into two the reason for whatever is observed, What types: () the colourless leucoplasts and (i) the would happen if these raisins are then pigmented chromoplasts. The colourless leucoplasts placed in concentrated salt solution? store starch, oil and protein granules whereas the oj, (3) * Lysosomes are membrane-bound sacs filed wih pigmented chroloplasts have different colours and can hydrolytic digestive enzymes. These enzymes at be of several ryps. made by rough endoplasmic reticulum. ‘The most important ones are those containing the * Lysosomes are a kind of waste disposal system of pigmene chlorophyll, known as chloroplasts, which is the cll Tesponsile forthe preparation of food - by + During the disturbance in cellular metabolism, photosynthesis Other chromoplasts contain nonepicen g. when a cell gots damaged, Iysosomes pret Pigments, which are responsible forthe characteristic in the cell may burst and che enzymes diges te Colours of fis and flowers eg anchoeyani, araged cell: Hence, hnomomes rea cle ‘suicidal bags’ ofa cell 8 How are the following related to each other? * Lysosomes break up the foreign mate (i) Chromatin network and chromosomes entering into the cell, such as bacteria of fad (ii) Chloroplast and chlorophyll into small pieces. il) Genes and DNA CBSE2016 (GA The raisins will swell up due to endosmosis. If Sol, (The cell contains nuclear material which can be seen these raisins are again placed in concentrated st Ee ae ee eee Been solution, they will shrink, due to exosmosis por diding Ths chromatin mci gesarginied 10, Discuss in detail the importance of mito pee cod eres and meiotic cell division, CBSE 2016, Sol, Referto texton Py 109.