Biology - B2.3 - Enzymes - Revision Cards in GCSE Biology

B2.3.1 - Proteins, Catalysts and Enzymes

Protein molecules - long chains of amino acids folded to make specific shape - shape depends on function - can be: structural components of tissues, eg. muscle, hormones, antibodies, catalysts
Large proteins that control chemical reactions in cells called enzymes
Enzymes - biological catalysts - speed up reactions
Enzyme shape is vital for function - shape has an area where molecules can fit - active site
Substrate in a reaction held in active site can be connected to another molecule or broken down
Enzymes can:
- build large molecules from smaller ones - build starch from glucose
- change one molecule to another - one type of sugar to another
- break down large molecules to smaller ones - all digestive enzymes

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Enzyme reactions - similar to other reactions when temperature is increased
Reactions happen faster when warmer - higher temperature = molecules move around quicker = more collisions more often with more energy
Temperature too hot = enzyme stops working as active site changes shape - denatured
Each enzyme works best in different pH values - some in acidic, eg. stomach, others neutral or alkaline
pH too acidic/alkaline for enzyme = active site changes shape - denatured

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Some enzymes work outside cells - digestive enzymes are produced by specialised cells in glands and the gut lining -> enzymes pass out of cells and come into contact with food
Digestion - involves breakdown of large insoluble molecules to smaller soluble molecules
Amylase - a carbohydrase - produced by salivary glands, pancreas and small intestine - catalyses digestion of starch to sugars in mouth and small intestine
Protease - proced by stomach, pancreas and small intestine - catalyses breakdown of proteins to amino acids in stomach and small intestine
Lipase - produced by pancreas and small intestine - catalyses breakdown of lipids (fats and oils) to fatty acids and glycerol

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Protease - in stomach - works best in acidic conditions - glands in stomach wall produce hydrochloric acid to create very acidic conditions
Amylase and lipase - in small intestine - work best in slightly alkaline conditions
Liver produces bile - alkaline - stored in gall bladder - squirted into small intestine and neutralises stomach acid - makes small intestine conditions slightly alkaline

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Some microorganisms produce enzymes that pass out of their cells - many uses in industry but can be costly to produce
Biological detergents - contain protease and lipase that digest food stains - work at lower temperatures - saves energy and money on electricity
Proteases - used to pre-digest some baby foods
Isomerase - used to convert glucose syrup to fructose syrup - more sweeter = less needed = not as fattening
Carbohydrase - used to convert starch to sugar syrup for food
Enzymes used in industry to bring about reactions at normal temperatures and pressures - traditional chemical processes require expensive equipment and lots of energy to produce high temperatures and pressures

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Adv of using enzymes:
- very effective at removing stains as washpowders
- washpowders work at lower temperatures - saves energy and money
- used in medicine to diagnose, control and even cure diseases
- cost of equipment and energy reduced in industry
Disadv of using enzymes:
- misusing washpowders can mean allergic reactions - enzymes inclosed in capsules and hands shouldn't be put under water if powder dissolves
- enzymes may enter waterways via sewage system
- industrial enzymes can be costly to produce
- high temperatures - needed to kill pathogens but enzymes denature
- protease will digest some fabrics, eg. wool

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