Secondary 2 Biology Notes Chapter 2 Food and nutrition Topic 2.1 Making food from sunlight Terms to Study 1. Photosynthesis: the process of forming sugars from carbon dioxide and water using light energy 2. Chlorophyll: a chemical that traps light energy for use in photosynthesis Detailed process of photosynthesis - light shines onto the leaf and it is trapped by the chlorophyll in the chloroplasts of the palisade cells - the chloroplast uses light energy to split water molecules into oxygen and hydrogen - then chloroplast combines the hydrogen with carbon dioxide to form sugars (glucose) - oxygen is released into the air through stomata as waste products - glucose is turned into starch to be stored for a short time by the leaf cell Secondary 2 Biology Notes Experiment to show that light is necessary for plants. Experiment procedure - Cut a simple shape from a piece of aluminum foil to make a stencil and attach it to a destarched leaf - After 4 to 6 hours of daylight, remove the leaf and test it for starch. Result: Only the areas which had received light go blue-black with iodine. Secondary 2 Biology Notes A section through a leaf Main Parts of a leaf Functions Upper epidermis Transparent to let light through Contains cuticle (waxy layer); waterproof layer Mesophyll Palisade mesophyll layer - Contains palisade cells: main site for photosynthesis Spongy mesophyll layer - Contains spongy cells: less tightly packed (air spaces allow gases into all cells) Vein: - Xylem: carries water into a leaf - Phloem: carries sugars away from leaf Lower epidermis Contains stoma which allows gases in or out of leaf controlled by guard cells Secondary 2 Biology Notes Use of glucose in plants: - Converted to sucrose to carry away from leaf - Stored as starch - Converted to cellulose - Fats and oils - Protein (glucose + nitrates) - Chlorophyll (glucose + nitrogen + magnesium) Secondary 2 Biology Notes Chapter 2 Food and nutrition Topic 2.2 Gaining water and nutrients Terms to Study 1. Osmosis: the movement of water from an area of high water concentration to an area of lower water concentration through a partially permeable membrane 2. Diffusion: the movement of particles from an area of high concentration to an area of lower concentration 3. Active transport: the movement of particles against the concentration gradient, through a cell membrane, using energy 4. Transpiration: the evaporation of water from a plant 5. Transpiration stream: movement of water through a plant from roots to leaves and loss from the leaf Uptake of water - water moves from the soil into root hairs (by osmosis), then cells to cells unit it reaches the xylem vessels in the roots - it is pulled up the plant to the leaves using the force from transpiration Secondary 2 Biology Notes What is water needed for? 1. As a solvent: to let all the other substances dissolve and be carried 2. As a reactant: part of a chemical reaction 3. As a coolant: evaporation of water from leaves (transpiration) 4. For support: water fills up the cells creating push against the cell wall (become firm) Uptake of mineral salts - when mineral ions are abundance in the soil → the root hair cells use diffusion first to take in mineral ions - if a mineral salt is low in the soil → the root hair cells take in mineral ions using energy (active transport) Mineral salt Compound in plant Use in the plant nitrate proteins growth of new cells phosphate ATP chemical energy in cells potassium enzyme activators helps reactions of photosynthesis magnesium chlorophyll traps light in photosynthesis Secondary 2 Biology Notes Chapter 2 Food and nutrition Topic 2.3 Human food and diet Terms to Study 1. Carbohydrate: chemical made up from carbon, hydrogen and oxygen atoms, used for energy by organisms 2. Proteins: chemicals made from chains of amino acids and used for growth and repair by the body 3. Fats: chemicals that are used to store energy in organisms 4. Vitamins: chemicals needed by a person in small amounts to keep healthy 5. Mineral salt: soluble chemical needed by plants and animals in small amounts 6. Fiber: the part of food that cannot be digested 7. Balanced diet: a diet containing all that is needed by a person in the amounts needed 8. Deficiency disease: a type of disease caused by the lack of a substance in the diet 9. Malnourishment: health problems that are caused by a diet lacking in some nutrients Seven nutrient groups: - Carbohydrates - Fats - Proteins - Vitamins - Minerals - Fiber - Water Secondary 2 Biology Notes Nutrient Elements contained Carbohydrates Fats Proteins Smaller units Functions C,H,O Simple sugars provide instant energy and carbon, hydrogen, oxygen (glucose) energy storage (17kJ/g) C,H,O Fatty acids energy storage, making cell carbon, hydrogen, oxygen and glycerol membranes (34kJ/g) C,H,O,N,S Amino acids growth and repair (17kJ/g) carbon, hydrogen, oxygen, nitrogen, sulfur Food Tests Nutrient Test Name Positive Results Negative Results Sugar Benedicts’ test Red Blue Starch Iodine test Blue-black Straw color Fats Emulsion test Water becomes cloudy Water remains clear Proteins Biuret test Violet / purple / lilac Pale blue Mineral salts - Calcium: for the structure of bone and teeth - Iron: for carrying oxygen in red blood cells - Sodium: for keeping the correct concentration of substance in cells - Phosphorus: for energy release - Potassium: to help the chemical reactions in cells Secondary 2 Biology Notes Deficiency diseases 1. Anemia → lack of iron 2. Rickets → lack of calcium 3. Scurvy → lack of vitamin C Vitamins - cannot be made in our body - none of them provide energy Fiber (from cellulose cell wall) - the body cannot digest and helps the movement in the alimentary canal - encourages right types of bacteria to grow in the large intestine - prevent diarrhea or constipation and colon cancer Water - solvent, transport, reactant, coolant Balanced diet - A diet containing all of the nutrient that is needed by a person in the amounts needed Carbohydrates - Too much energy consumption can lead to obesity and causes heart diseases Fats Sodium - Too little food causes tiredness - Eating sugar can lead to tooth decay - Too much fat can narrow and block the blood vessels - Blood clot stuck in brain → stroke - Blood clot stuck in heart muscle vessels → heart attack - Too much salt can lead to high blood pressure Secondary 2 Biology Notes Chapter 2 Food and nutrition Topic 2.4 Digestion in humans Terms to Study 1. Ingestion: the taking in of food into the mouth 2. Digestion: the breaking down of large food substances into small, soluble molecules for absorption into the blood 3. Absorption: the taking in of soluble materials into the blood 4. Egestion: the getting rid of undigested food that has not been absorbed into the cells of the body 5. Peristalsis: the process of moving something along a tube by a wave of contracting muscles passing along the length 6. Enzymes: chemicals that speed up chemical reactions in cells Generalized alimentary canal processes Ingestion → Digestion → Absorption → Egestion The digestive system pathway (*label) Mouth → Oesophagus (foodpipe/gullet) → Stomach → Small intestine (duodenum, ileum) → Large intestine (colon, rectum, anus) Main digestive organs Mouth Food pipe Stomach Small and large intestines Associated digestive organs Liver and pancreas Secondary 2 Biology Notes Parts of alimentary canal Mouth Functions Teeth - Chewing: which breaks down food into smaller pieces and to mix the food with saliva Saliva - contains amylase enzymes which break down starch Oesophagus (transports food Peristalsis in the mouth to the stomach) - the process of moving something along a tube by a wave of contracting muscles passing along the length Stomach - contains gastric juice (hydrochloric acid) → kills most microorganisms in the food - chemical digestion: protease enzymes break down proteins Small intestine - the acidic food from the stomach is neutralized by alkaline secretions from liver (bile) and pancreas - bile is not an enzyme - most digestion takes place - food absorption also takes place (contains villi and microvilli to absorb soluble food molecules) Large intestine - where most water is absorbed into the blood - some bacteria in the large intestine used the remains of food to make some vitamins the body needs - faeces are stored in the rectum - undigested food (faeces) are egested through anus Secondary 2 Biology Notes Enzymes - are proteins - substances that speed up chemical reactions - each has a very specific shape - building up (anabolic) - breaking down (catabolic) The surface area of the small intestine is increased by: - It is long - The absorbing surface is folded - On the folds are villi - Each villus has tiny projections called microvilli