Chapter 9 Enzymes

Metabolism –The sum of all the chemical reactions that take place within an organism.

e.g. growth, movement etc. Metabolism maintains a balanced internal state in an organism (homeostasis).

Sources of Energy

a) Solar Energy – Energy from the Sun. Primary source of energy for life, plants carry out photosynthesis using this sunlight energy to make chemical energy (stored as food).

b) Cellular Energy – Is energy stored in the bonds of biomolecules e.g. carbohydrates and lipids. Each organism breaks down biomolecules in respiration and this releases energy which is either used by the cell or released as heat.

Enzymes

Enzymes are catalysts made of protein. They are proteins that speed up a reaction with being used up in the reaction.

A catalyst is a substance that speeds up a reaction, without itself being used up in the reaction.

Enzymes are often called biological catalysts.

Enzymes speed up a chemical reaction and allows the reaction to take place at normal cell temperatures.

Enzymes are made up of chains of amino acids and then folded into a 3 dimensional shape. The 3-D shape means that enzymes will only react with a substance that has a shape that matches a particular enzyme.

Anything that changes the shape of an enzyme e.g. pH or temperature reduces its efficiency.

Features of Enzymes

1. Enzymes are made of protein.

2. Enzymes need the correct shape to

fit their substrate

3. Enzyme reactions are reversible

(an enzyme can cause a reaction to proceed in

either direction).

Examples of enzyme catalysed reactions

The Role of Enzymes

Enzymes are necessary in plants and animals to control metabolic reactions.

a) Catabolic Enzymes – enzymes that break down large molecules into smaller molecules e.g. Amylase. It converts starch to maltose in the mouth and duodenum.

b) Anabolic Enzymes – Enzymes that convert simpler molecules into more complex molecules. E.g. DNA ligase enzyme is used in genetic engineering to join two pieces of DNA together.

Factors Affecting Enzyme Activity

A denatured enzyme has lost its shape and can no longer function.

Enzymes work best under ideal conditions e.g. a particular temperature and pH. Any change in these conditions will affect the rate of reaction.

1. TemperatureAt very low temperatures e.g. O C enzymes do

not work. As the temperature increases the rate

of enzyme reaction increases.

Human enzymes work best at 37C. Most plant enzymes

work best at 20-30C. Above a certain temperature

enzymes begin to lose their 3-D shape and the rate

of reaction decreases and the enzyme becomes

Denatured.

2. pH

pH scale runs from 0 to 14. Enzymes

Are sensitive to changes in pH. Most enzymes

work best at pH 6-8, outside this pH range

The activity of the enzyme falls rapidly

Immobilised Enzymes

Bio-processing involves the use of enzyme controlled reactions to produce a product.

e.g. Traditionally bioprocessing involves the use of micro-organisms e.g. yeast or bacteria to produce foodstuffs eg. Cheese, yoghurt, bread etc.

In recent times bioprocessing has been used to develop products like antibiotics, vaccines etc.

A bioreactor is a vessel or container in which living cells or their products are used to make a product.

Enzymes are immobilised (fixed into place) in a bioprocessing reaction because using free enzyme is very wasteful.

Uses of Immobilised Enzymes

1. Fizzy drinks are often sweetened with a sugar called fructose (sweeter but more expensive than glucose) . An enzyme called glucose isomerase is used to convert glucose to fructose.

2. Penicillin acylase is very expensive enzyme used to alter the structure of the antibiotic penicillin to make new antibiotics. It is used in an immobilised form.

3. Lactase is an expensive enzyme which is used to convert lactose sugar into two sweeter sugars (glucose and galactose) which are used in making toffee and caramel.

Enzyme Experiments

In each experiment one factor (pH, temperature, enzyme concentration, substrate concentration) is varied (changed)

Activity 10: To prepare an enzyme immobilisation and examine its application

The drops of liquid coming out of the separating funnel are tested with clinistix (sticks to test for glucose). The stick will turn from purple to pink if glucose is present.

Result: The free yeast/water in the control solution will form a cloudy product and the immobilised yeast enzyme will form a clear product. The glucose product will form faster in the free yeast/water reaction.