- Created by: maddieecarr
- Created on: 26-11-19 15:03
B3.1: Tissues and Organs
- a tissue is a group of cells with similar structure and function.
- organs are collections of tissues performing specific functions.
- organs are organised into organ systems, which work together to form organisms.
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B3.2: The Human Digestive System
- organ systems of organs that perform specific functions in the body.
- the digestive system in a mammal is an organ system where several organs work together to digest and absorb food.
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B3.3: The Chemistry of Food
- carbohydrates are made up of units of sugar.
- simple sugars are carbohydrates that only contain one or two sugar units. they turn blue Benedict's solution brick red on heating.
- complex carbohydrates contain long chains of simple sugar molecules bonded together. starch turns yellow-red iodine blue black in its presence.
- lipids consist of three molecules of fatty acid bonded to a molecule of glycerol. the ethanol test indicates the presence of a lipid in solutions.
- protein molecules are made up of long chains of amino acids. Biuret reagent turn blue to purple in the presence of proteins
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B3.4: Catalysts and Enzymes
- catalysts increase the rate of chemical reactions without chemically changing.
- enzymes are biological catalysts and catalyse specific reactions in living organisms due to the shape of their active site. This is the lock and key theory of enzyme action.
- enzymes are proteins. the amino acid chains are folded to form the active site and match the shape of a specific substrate molecule.
- the substrate binds to the active site and the reaction catalysed by the enzyme.
- metabolism is the sum of all the reactions in a cell or the body.
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B3.5: Factors Affecting Enzyme Action
- enzyme activity is affected by temperature and pH.
- high temperatures denature the enzyme, changing the shape of the active site.
- pH can affect the shape of the active site of an enzyme and make it work very efficiently or stop it working.
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B3.6: How the Digestive System Works
- digestion involves the breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine.
- digestive enzymes are produced by specialised cells in glands and in the lining of the digestive system.
- carbohydrases such as amylase catalyse the breakdown of carbohydrates into simple sugars.
- proteases catalyse the breakdown of proteins into amino acids.
- lipases catalyse the breakdown of lipids into fatty acids and glycerol.
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B3.7: Making Digestion Efficient
- the protease enzymes of the stomach work the best in acid conditions. the stomach produces hydrochloric acid which maintains a low pH.
- the enzymes made in the pancreas and small intestine work best in alkaline conditions.
- bile produced in the liver, stored in the gall bladder and released through the bile duct neutralises acid and emulsifies fat.
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