GCSE AQA Biology 2 Enzymes, Digestion & Enzyme Uses

Enzymes have special shapes
1. Chemical reactions involve splitting apart/joining together
2. Each enzyme has unique shape that fits onto substance involved in reaction
  1. Enzymes usually only catalyse 1 reaction - substance has to fit special shape
Enzymes
1. Chemical reactions need to be carefully controlled
  1. Could increase rate of reaction by raising temp. but would not be specific & cells could get damaged
2. Living things produce enzymes that act as biological catalysts
  1. Catalyst: substance which increases speed of reaction, without being changed/used up in reaction
3. Enzymes are proteins (made up of chains of amino acids folded into unique shape)
  1. Proteins also act as structural components of tissues, hormones & antibodies
Enzymes need the right temp. and pH
1. Temperature
  1. Higher temp. increases rate at first
    1. Too hot, bonds holding enzyme together break, destroys active site - denatured
  2. Enzymes in human body normally work best at around 37 degrees C
2. pH
  1. Too high or low - interferes with enzyme bonds, changing shape & denaturing enzyme
    1. All enzymes have optimum pH, often pH 7
Digestive enzymes
1. Starch, proteins and fats are molecules that are too big to pass through digestive system walls
  1. Digestive enzymes break them into smaller ones that can pass through
2. Amylase
  1. Converts starch into sugars
    1. Made in: salivary glands, pancreas & small intestine
3. Protease
  1. Converts proteins into amino acids
    1. Made in: stomach, pancreas & small intestine
4. Lipase
  1. Converts lipids into glycerol & fatty acids
    1. Made in: pancreas & small intetsine
Bile
1. Produced in liver, stored in gall bladder before release into small intestine
2. Hydrochloric acid in stomach makes pH too acidic for enzymes in small intestine to work properly
  1. Bile is alkaline - neutralises acid to make conditions alkaline so enzymes work best
3. Emulsifies fats - breaks fats into tiny droplets
  1. Bigger SA of fat for lipase to work on - makes digestion faster
Digestive system
1. Enzymes
  1. Produced by specialised cells in glands & gut lining
  2. Catalyse breakdown of different food molecules
2. Salivary glands
  1. Produce amylase in saliva
3. Gullet
  1. Oesophagus
4. Stomach
  1. Pummels food with muscular walls
  2. Produces protease (pepsin)
  3. Produces hydrochloric acid to kill bacteria & give right pH for pepsin (pH 2)
5. Liver
  1. Produces bile
6. Gall bladder
  1. Bile is stored
7. Pancreas
  1. Produces protease, amylase & lipase
8. Small intestine
  1. Produces protease, amylase & lipase - where digested food is absorbed
9. Large intestine
  1. Excess water is absorbed
10. Rectum
  1. Where faeces is stored before release through anus
Enzymes are used in biological detergents
1. Enzymes - 'biological' ingredient
2. Mainly protease and lipase - break down plant & animal matter
3. More effective at lower temp. than other detergents
Enzymes are used to change foods
1. Proteins in baby food 'pre-digested' using proteases - easier for baby to digest
2. Carbohydrases can turn starch syrup into sugar syrup
3. Glucose syrup turned into fructose syrup using isomerase - fructose sweeter so can use less (good for slimming foods/drinks)
Using enzymes in industry
1. Advantages
  1. Specific - only catalyse the reaction you want them to
  2. Using lower temp. & pressure = lower cost - saves energy
  3. Work for long time - after initial cost, can use continually
  4. Biodegradable - less environmental pollution
2. Disadvantages
  1. People can develop allergies to enzymes
  2. Enzymes be denatured easily - by small increase in temp./poisons/changes in pH
    1. Conditions must be tightly controlled
  3. Can be expensive to produce
  4. Contamination of enzyme with other substances can affect reaction

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GCSE AQA Biology 2 Enzymes, Digestion & Enzyme Uses

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