Enzymes

AQA Unit 2 Additional Biology

Proteins have many functions, both inside and outside the cells of living organisms. Proteins, as enzymes, are now used widely in the home and in industry.

B2.5 Proteins – their functions and uses

You should be able to:■ evaluate the advantages and disadvantages of using enzymes in the home and in industry.

ENDOCRINE SYSTEM

Pituitary

Thickens womb wall

Insulin

Oral contraceptive

Travels in

e.g. e.g.

e.g. e.g

.

controls

secretes

used in

consists of

secrete

are

inhibits

secretes.

has

less

Bloodstream Blood sugar Chemical messengers FSH Glands LH Hormones Oestrogen Ovary Matures egg Pancreas Progesterone Releases egg Side effects

ENDOCRINE SYSTEM

Glands Bloodstream

Hormones

Matures egg

LH

Oestrogen

FSH

Ovary Pituitary

Thickens womb wall

Releases egg

Insulin

Pancreas

Oral contraceptive

Side effects

Progesterone

Travels in

e.g. e.g.

e.g. e.g

.

Blood sugar

controls.

secretes.

used in

consists of

secrete

Chemical messengers

are

inhibits

secretes.

has

less

Proteins

Structural tissues eg muscles

Antibodies Hormones Enzymes

Amino acids – about 20 different types

What are enzymes and what do they do?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.

PCRSTApH

arentsaneallytruggleottend ysics

PCRSTApH

roteinsatalystseusablepecificemperatureffected

2 main types of enzymes

• Catabolic enzymes which (break down) large molecules into smaller moleculese.g. digestion of starch by the enzyme amylase into glucose.

• Anabolic enzymes which (build up) small molecules to form larger moleculese.g. production of glucose during photosynthesis from carbon dioxide, water and light.

Catabolic enzymes Anabolic enzymes

enzymes

Break down Build up

Digestion Photosynthesis

Enzymes and activation energy

• 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 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

Structure of an enzyme molecule

How enzymes work

Step-by-step

• 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.

Complete Qu 1-8 page 12.

Enzymes

1. Enzymes ………….. up the rate of chemical …………………..

2. Enzymes are ………………….. because they only work on one substrate. 3. The substrate fits into the ………………….. site of the surface of the …………………...

4. With an increase in ………………….. the rate of reaction …………………..

5. Enzymes can be re-used, so only ………………….. amounts are needed.

6. To which group of chemical compounds do enzymes belong?

7. Why is an enzyme specific for a particular substrate?

8. Why can an enzyme be used again and again?

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.

11. A number of factors can alter the rate of an enzyme- controlled reaction. Say what each of the following would do to the rate of reaction and give your reasons.An increase in enzyme concentration …………………..…………………..…………………..…………………..…………………..…………………..…………………..…………………..

A decrease in temperature…………………..…………………..…………………..…………………..…………………..…………………..…………………..…………………..

A lowering of pH …………………..…………………..…………………..…………………..…………………..…………………..…………………..…………………..

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

The action of bile

• 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.

Lipase is an enzyme that breaks down fats. We can use an indicator to follow this reaction. The indicator is red to start with but turns yellow when all the fat has been broken down. Look at the results table below.

Test-tube Temp (°C) Original colour Final colour1 0 Red Red2 10 Red Orange3 40 Red Yellow4 60 Red Orange5 100 Red Red

What is the optimum temperature for lipase? …………………..

Why do you think the colour didn’t change in test tube 1? …………………..…………………..…………………..…………………..

Why do you think the colour didn’t change in test tube 5? …………………..…………………..…………………..…………………..

Predict what you think would happen if you warmed test tubes 1 and 5 up to 40 °C. Try to explain your prediction.

13 Which enzymes work on carbohydrates? …………………..

14. Which enzymes work on proteins? …………………..

15.Which enzymes work on fats? …………………..

Name the products which are formed in each case. …………………..…………………..…………………..…………………..

………………………………..…………………..…………………..…………………..……………

Name 3 functions of bile …………………..…………………..…………………..…………………..…………………..………………………..…………………..…………………..…………………..

…………………..…………………..…………………..…………………..……………

i) Some microorganisms produce enzymes that pass out of the cells. These enzymes have many uses in the home and in industry.

In the home:■ biological detergents may contain protein-digesting and fat-digesting enzymes (proteases and lipases)■ biological detergents are more effective at low temperatures than other types of detergents.

Advantages Disadvantages

These are more efficient at removing stains from clothes.

If the clothes are not fully rinsed, protease enzymes may remain in the clothes, which digests protein in the skin.

Lower washing temperatures can be used which saves energy.

This can lead to irritation, allergies and dermatitis.

In industry:

■ proteases are used to ‘pre-digest’ the protein in some baby foodsThis reduces how much the baby needs to digest the food

■ carbohydrases are used to convert starch into sugar syrup This is cheaper than extracting sugar from sugar cane

■ isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter and therefore can be used in smaller quantities in slimming foods.

Advantages Disadvantages

Enzymes enable industrial reactions to take place at lower temperatures.

Enzymes are sensitive to temperature and pH changes.

Supplying heat is expensive. When enzymes are used, industrial processes can be cheaper.

Temperature and pH need to be carefully monitored and controlled, which can be expensive.

j) In industry, enzymes are used to bring about reactions at normal temperatures and pressures that would otherwise require expensive, energy-demanding equipment. However, most enzymes are denatured at high temperatures and many are costly to produce.

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).

In 1989 a new fat digesting enzyme was found in a fungus. Its optimum pH is 7.5. It can act at low temperatures and after a few days, breaks down into carbon dioxide, nitrogen and water. Give 2 reasons why this enzyme is now used in washing powder …………………..…………………..…………………..…………………..……………. …………………..…………………..…………………..…………………..………………

Why would a washing powder of high pH or low pH be difficult to handle?

…………………..…………………..…………………..…………………..…………………………………..…………………..…………………..…………………..………………

Complete the diagram below to show how the three main food groups are broken down during digestion.

Amylase Amino acids Fat Fatty acids Glycerol Maltose Protease

Protein

Lipase

Protease

Amino acids

Fat Glycerol Fatty acid

Complete the diagram below to show how the three main food groups are broken down during digestion.

Amylase Amino acids Fat Fatty acids Glycerol Maltose Protease

Protein

Carbohydrate eg starch

Amylase

Maltose