B 2 Additional Biology

Enzymes are-•Protein molecules (made up of amino acids)•Biological catalysts (Increase the speed of chemical reactions)•Specific (Each one catalyses one particular reaction)•Reusable (Can be used again and again)•Affected by temperature and pH.•Found in animals, plants and microorganisms.

WHAT ARE ENZYMES AND WHAT DO THEY DO?

• Catabolic enzymes which (break down) large molecules into smaller molecules

• e.g. digestion of starch by the enzyme amylase into glucose.

• Anabolic enzymes which (build up) small molecules to form larger molecules

• e.g. production of glucose during photosynthesis from carbon dioxide, water and light.

2 MAIN TYPES OF ENZYMES

• Chemical reactions take place when particles collide with enough energy.

• The minimum amount of energy required is called the activation energy.

• Enzymes lower the amount of activation energy required, so the reaction can proceed at a greater rate.

ENZYMES AND ACTIVATION ENERGY

STRUCTURE OF AN ENZYME MOLECULE

• Enzymes are proteins made up on long chains of amino acids.

• These long chains fold to produce a special shape which is vital for the enzyme‘s function.

Active Site

HOW ENZYMES WORK

• Shape of the enzyme’s active site is complimentary to the shape of one particular substrate.

• The two bind together to form an enzyme-substrate complex.

• The reaction between them take place rapidly.

• The products are released from the enzyme’s active site.

• Now try Questions 1-8 on the worksheet.

STEP-BY-STEP

FACTORS AFFECTING ENZYME ACTION - TEMPERATURE

• Enzymes work faster as the temperature increases up to 40oC, but are eventually denatured at about 60oC.

• This is because the shape of the active site is lost.

FACTORS AFFECTING ENZYME ACTION – PH

• Each enzyme works best at a particular pH. This is known as the optimum pH.

• Extremes of pH will cause the active site to denature.

Now try Questions 8- 11 on your worksheet

ENZYMES IN DIGESTION

• Enzymes break down large insoluble food molecules into smaller, soluble ones which can be absorbed through the small intestine wall to enter the bloodstream.

• Different parts of the digestive tract have different pH conditions to enable different enzymes to work.

THE MAIN GROUPS OF DIGESTIVE ENZYMES

• Lipase enzymes digest fatty substrates.

• Protease enzymes digest protein substrates.

• Carbohydrase enzymes digest carbohydrate substrates.

Substrate Enzyme Product Where enzyme produced

Optimum pH

Starch Amylase (a carbohydrase)

Glucose Salivary glands & pancreas

pH7

Protein Trypsin(a protease)

Amino acids

Stomach, pancreas, & small intestine

pH3

Lipids Lipases (fats)

Fatty acids & glycerol

Pancreas pH8

• It’s produced by the liver and is stored in the gall bladder which, squirts it into the small intestine.

• It’s alkaline to neutralise acidic chyme coming from stomach.

• It emulsifies fats to break them into smaller droplets which increases the surface area for lipase enzymes to work.

THE ACTION OF BILE

COMMERCIAL USE OF ENZYMES

Product Enzymes Explanation

Biological washing powder

Lipases and proteases.

Digest biological stains off clothes.

Baby food Proteases Pre-digest protein to make digestion easier for babies.

Slimming foods Isomerase (carbohydrase)

Converts glucose into fructose (less of which is needed to sweeten food).

Now try Questions 12- 17on worksheet.