Biology Examination Notes
Osmosis
- Movement of water molecules from high to low water concentration gradient through
a semi-permeable membrane (Membrane in which only small molecules can pass through)
- Passive Transport
Isotonic Solution = Concentration of water inside and outside of the cell is the
same
Hypotonic Solution = Concentration of water outside is higher than inside the
cell, meaning water enters the cell, which makes the cell
burst (animal cells) or become turgid (plant cells)
Hypertonic Solution = Concentration of water inside the cell is greater than
outside cell, meaning water leaves the cell, making the cell
plasmolysed (plant cells) or shrink (animal cells)
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Diffusion
- Movement of any substances from high to low concentration
- Passive transport
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Active Transport
- Movement of mineral ions from low to high concentration using energy
Examples: Plant --> Root hair cells absorbing mineral ions
Animal --> Absorption of glucose and amino acids in small intestine
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Biological Molecules
Carbohydrates/Starch = Carbon, Hydrogen, Oxygen (CHO)
Fat = Carbon, Hydrogen, Oxygen (CHO)
Proteins = Carbon, Hydrogen, Oxygen, Nitrogen (CHON)
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Types of saccharides
Polysaccharide ---> Contains more than 2 glucose molecules (Carbohydrates, Starch
in chloroplasts, Glycogen in liver, Cellulose)
Disaccharide ---> Contains 2 glucose molecules (Maltose, Lactose, Sucrose)
Monosaccharide ---> Contains 1 glucose molecule (Glucose, Galactose, Fructose)
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Nutrients
- Compounds in food essential to life and health
- Provides us with energy
- Building blocks of repair and growth
- Substances necessary to regulate chemical processes
Classification for essential nutrients
Macronutrients ---> Carbohydrates, Proteins, Fats, Fiber and Water
Micronutrients ---> Vitamins, Minerals
The 7 Major nutrients:
- Carbohydrates
- Fats
- Proteins
- Vitamins
- Minerals
- Fibers
- Water
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Carbohydrates O-O-O-O-O
- Provide energy (65%)
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Types of Carbohydrates
- Simple Carbohydrate (Sugar) : Quick energy source, short term
Do not supply other nutrients or fibers
Etc. Candy, Milk, Yogurt, Fruits, Soda, Jelly
- Complex Carbohydrate (Starch): Longer lasting energy
Supplies other nutrients and fibers
Etc. Potatoes, Cereals, Rice, Bread
Excess amounts of Carbs ---> Weight gain, Diabetes, Mellitus
Deficiency of carbs ---> Constipation, Low mental performance
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Fats
- Insulation, provides substances for growth and healthy skin
- Protects the internal organs
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Types of Fat
- Saturated fat (solid): Diary products, Meat, Coconut and Palm oils
- Unsaturated fat (liquid): Vegetable oil, Fish oil, Nuts and seeds
Excess amounts of fat ---> Weight gain, Elevated blood lipid, Coronary heart
diseases
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Proteins
- Growth and repair of cells
- Two types of proteins ---> Structural proteins (Collagen, keratin)
---> Functional proteins (Hormones, enzymes, haemoglobin,
antibodies)
Deficiency of protein ---> Kwashiorkor (1-5 years old, swelling belly)
---> Marasmus (<1 year old)
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Vitamins
- Required for growth and development
Sources: Fat soluble vitamins ---> Vitamin A, D, E, K
Water soluble vitamins ---> Vitamin B, C
Fruits and vegetables
Types of Vitamins ---> A, B, C, D, E, K
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Minerals
- Help to regulate activity of cells
Types of minerals ---> Calcium, Potassium, Iron, Iodine
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Fibers
- Get rid of undigested food
Two types of fiber ---> Soluble fiber: Dissolves in water to form a gel-like
material
---> Insoluble fiber: Promotes the movement of materials through
your digestive system
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Water
- Essential for: Digestion
Absorption
Circulation
Regulation of temperature
Transportation of nutrients, oxygen and wastes
Source: Water, Fruits and vegetables
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Nutrient Deficiencies
Vitamin A deficiency = Poor eyesight, skin problem
Sources = Yellow/Orange fruits and vegetables, Pears
Vitamin B deficiency = Beriberi
Sources = Yeast, milk, eggs, banana
Vitamin C deficiency = Poor wound healing, Anemia, Heart problem, Scurvy (Bleeding
gums)
Sources = Yellow/Orange fruits and vegetables, Pears
Vitamin D deficiency = Bone disorder (Ricket)
Sources = Diary products, Seafoods, Sunshine
Vitamin E deficiency = Skin disease
Sources = Nuts, Seeds and grains
Vitamin K deficiency = Poor blood clotting and poor body repair
Sources = Dark green food, Cauliflower
Calcium deficiency = Ricket
Sources = Milk, Broccoli
Potassium deficiency = Nervous disorder
Sources = Oranges, Pears, Apples
Iron deficiency = Anemia
Sources = Eggs, Dark leafy vegetables, Red meat
Iodine deficiency = Thyroid cancer
Sources = Saltwater fish, salt
Fiber deficiency = Constipation, bowel cancer
Sources = Whole-wheat flour, wheat bran, nuts, beans and vegetables
(cauliflower, green beans and potatoes)
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Food Tests
Starch test = food sample + Iodine ---> Blue-black, dark blue (+)
---> Yellow, Orange, Brown (-)
Glucose test = food sample + Benedict's + Heat ---> Green, Yellow, Orange, Red,
Brick-Red (+)
---> Blue (-)
Protein test = food sample + Biuret ---> Purple (+)
---> Blue (-)
Fat test = food sample + Ethanol(Alcohol) + Water ---> White emulsion/cloudy/milky
(+)
---> Colourless (-)
Vitamin C test = food sample + DCPIP ---> Colorless (+)
---> Blue (-)
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Enzymes
- Protein macromolecules
- Biological catalysts (speeds up the rate of chemical reactions without being
changed by itself)
Enzyme specificity
- Enzymes are specific to one particular substrate.
- Enzymes have complementary shape, called lock-and-key hypothesis.
- When substrate binds to the active site of the enzyme, it forms the enzyme-
substrate complex.
- After the reaction, the products leave the active site of the enzyme.
Factors that affect the rate of enzyme activity
- Temperature
- pH
- Amount of substrate
- Amount of enzyme
Enzyme activity
- When lower than the optimum temperature, the enzyme activity is slow due to less
kinetic energy and fewer collisions.
- At optimum temperature, the enzyme activity is the highest because there is more
kinetic energy and more collisions.
- When higher than the optimum temperature, the enzyme activity is decreased and no
reactions can occur due to the active site of the enzyme being denatured.
- Denature means the change in shape of the active site, meaning that the substrate
cannot fit into the active site of the enzyme.
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Digestive System
- a long muscular tube that begins with the mouth and ends with the anus
All parts of the digestive system:
- Mouth
- Pharynx
- Esophagus
- Stomach
- Liver
- Small Intestine
- Large Intestine
- Anus
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Mouth
- Performs both types of digestions; mechanical digestion, chemical digestion.
Chemical digestion: Breakdown insoluble molecules into soluble molecules using
enzymes,
with chemical changes and new products formed.
Mechanical digestion: Breakdown large pieces into smaller pieces without using
enzymes,
without chemical changes and no new products formed.
- Teeth chew food into smaller pieces by mechanical digestion.
Teeth
- 4 types of teeth: Molars and Pre-molars(Chewing and grinding up food)
Incisors (Biting and cutting)
Canines (Pointed for tearing)
- 3 parts to every tooth: Crown (portion above the gum line)
Root (embedded in the gum)
Neck (between the crown and root)
- Interior anatomy: Enamel --> Hardest white outer part of the tooth
Dentin --> Yellow bone-like material
Pulp --> Hollow region inside the tooth
Cementum --> Layer of connective tissue that binds the gums and
jawbone
- Salivary gland secretes salivary amylase, which breaks down carbohydrates into
glucose/maltose by chemical digestion.
Carbohydrates/Starch --Salivary Amylase(mouth)--> maltose/glucose (pH-7)
(Salivary Gland)
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Esophagus
- A straight muscular tube which connects the mouth with the stomach.
- Performs peristalsis to propel food and liquid down the esophagus into the
stomach.
Peristalsis: Circular muscle contract, longitudinal muscle relax
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Stomach
- Secretes gastric juice (HCl, enzymes and water)
- HCL kills pathogens and provide suitable pH for pepsin enzyme, created by the
stomach wall.
- Converts bolus into a liquid (chyme) after 4 hours of digestion.
Proteins --Pepsin(Stomach)--> Amino acids/Peptides (pH-2)
Stomach wall
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Small intestine
- Has three parts: Duodenum (where digestion takes place)
Jejunum
Ileum (where absorption takes place)
- The place where all three nutrients get broken down chemically, by enzymes such
as Pancreatic amylase, Trypsin and Lipase
Carbohydrates --Pancreatic Amylase(Small Intestine)--> Glucose (pH-7)
Pancreas
Proteins --Trypsin(Small Intestine)--> Amino acids (pH-9)
Pancreas
Fat --Lipase(Small Intestine)--> 3 fatty acids, 1 glycerol (pH-9)
Pancreas
Ileum
- Has various villi and microvilli
- Wall of villus has one layer of epithelial cells for faster rate of absorption
- Network of capillaries to absorb glucose and amino acids
- Has lacteal to absorb fatty acids and glycerol
- Has hepatic portal vein that sends nutrients to the liver
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Liver
- Creates bile, which is stored in the gall bladder
Bile: Breaks down large fat globules into smaller fat droplets.
Neutralizes pH for optimum enzyme pH in the small intestine
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Large Intestine
- Consists of the caecum, colon, rectum and anus
- Reabsorption of water and mineral salts
- Egestion of undigested food (feaces)
- Rectum stores feaces
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Stages of food breakdown
• Ingestion - the taking of substances, e.g. food and drink, into the body
through the mouth
• Digestion is the breakdown of the large foods into small foods.
• Absorption - the movement of small food molecules and ions through
the wall of the intestine into the blood
• Assimilation - the movement of digested food molecules into the cells
of the body where they are used, becoming part of the cells. (Occurs in the liver)
• Egestion - the passing out of food that has not been digested or
absorbed, as faeces, through the anus
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Formulas
- Percentage change = Final Value - Initial Value / Initial Value x 100%
- Surface area = 6 x a x a (a = area)
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