B5 & B6

• what is photosynthesis?

  the process by which plants synthesize carbohydrates from raw materials using energy from light
• word equation for photosynthesis

  carbon dioxide + water --> glucose + oxygen
• chlorophyll transfers energy from light into energy in carbohydrates
• the carbohydrate glucose is made in photosynthesis. it can be used to release energy in respiration. glucose can be used to make starch for storage of energy and sucrose for transport
• glucose can be used to make amino acids and proteins, using nitrogen obtained from nitrate ions . it can also be used to make chlorophyll, using nitrogen and also magnesium ions
• cellulose is used to build cell walls, sucrose is used for transport in the phloem, and nectar attracts insects for pollination
• leaves have a large surface area, to capture energy from sunlight and to increase absorption of carbon dioxide from the air. stomata on the Lower epidermis allows carbon dioxide to diffuse into the air spaces and then to the cells in the palisade mesophyll layer, where most photosynthesis takes place
• how to test a leaf for starch?

  boil the leaf to break down cell membranes, then heat it in alcohol to remove the chlorophyll. finally add iodine solution and if it turns blue black it contains starch
• what does a balanced diet contain?

  proteins, carbohydrates, fats and oils, water, minerals, vitamins and fibre
• scurvy is caused by a lack of vitamin c, and rickets by a lack of vitamin d
• what is the digestive system made up of?

  the mouth, salivary glands, oesophagus, stomach, small intestine and large intestine (alimentary canal). also the liver, gall bladder and pancreas
• what are the processes of the digestive system?

  ingestion, digestion, absorption, assimilation and egestion
• physiscal digestion is done by the teeth and stomach. it involves breaking down food into smaller pieces without chemical change to the food molecules. it increases surface area of food for the action of enzymes in chemical digestion
• chemical digestion is done by enzymes in the mouth, stomach and small intestine. it involves breaking down large molecules of nutrients to small ones, so that they can be absorbed
• in chemical digestion: amylase breaks down starch to simple reducing sugars, protease breaks down proteins to amino acids and lipase breaks down fats to fatty acids and glycerol
• hydrochloric acid in the stomach provides a low pH for enzymes to work, and also kills harmful microorganisms in food
• we can use an aquatic plant to measure the rate of photosynthesis, by counting the number of bubbles given off in unit time or by measuring the volume of gas given off