Enzymes

Question 1

What enzymes break down blood & grass

Answer 1

Blood - protease

Grass - carbohydrease

Question 2

Suggest two advantages of the enzyme in many washing powders being able to work effectively at less than 40*c

Answer 2

It is cheaper to wash

Question 3

Explain why washing powder with only protease enzyme would not remove grease and fat stains

Answer 3

Enzymes are specific, you would need lipase to break down fat

Question 4

If the temperature of the wash was changed from 45c to 20c or 70*c would the protease react quicker or slower

Answer 4

20*c - slower the enzyme & substrate would have less kinetic energy & less collisions between them therefore less product is formed

70*c - slower - the enzyme is denatured the active site has changed shape

Question 5

Would the protease work quicker or slower if the washing powder was slightly acidic?

Answer 5

Slower - it likes alkaline conditions so would be denatured in acidic conditions

Question 6

Some fabrics such as silk and wool (made up of animal protein) should be hand washed with soap powders not biological powders. Why?

Answer 6

Protease enzymes in the washing powder would digest the proteins in the silk and wool

Question 7

What are enzymes?

Answer 7

Enzymes are proteins that act as biological catalysts. They speed up the rate of biological reactions, which take place inside living cells, without being used or changed themselves

Question 8

Explain catabolic & anabolic reactions

Answer 8

Enzymes can catalyse a breaking down (catabolic) reaction like digestion

Or a building up reaction (anabolic) like starch molecules being built up from glucose molecules inside plant cells.

Without enzymes most of the reactions in any living organism would occur to slowly for organisms to function.

Question 9

What is a substrate?

Answer 9

The substance that an enzyme acts upon

Question 10

What is the product?

Answer 10

The new substance or substances formed as a result of the reaction

Question 11

Explain the mechanism of enzyme action

Answer 11

All enzymes are substrate specific because they have a specific shape. This shape creates an area known as the active site. It is here at the active site that the enzyme reacts with the substrate to break it down or put it together.

Only one substrate is the correct shape to fit into the active site of an enzyme and therefore enzymes only catalyse one or a few reactions. Hence there so thousands of different enzymes in the body. E.g. Lipase will only react with lipids - it will have no effect on proteins

Question 12

Explain the lock and key theory

Answer 12

The principle of enzyme specificity is explained by the lock and key theory due to the fit between the active site and the substrate. It proposes that the active site of an enzyme has a specific shape (like a lock) into which only on specific molecule (the key) fits exactly.

Question 13

Explain commercial enzymes

Answer 13

Many enzymes have commercial uses. For example, many biological washing powders have enzymes for breaking down stains which are difficult to remove. These enzymes are thermostable (they can work over a wide range of temperatures) and they break (digest) the complex, large and insoluble stains down into small. Soluble molecules that dissolve in water.

Question 14

Explain types of enzymes

Answer 14

Enzymes are made inside cells. The enzyme may then leave the cell and do its job outside. These enzymes are called extra cellular enzymes e.g. Digestive enzymes which break down food substances in the gut.

Other enzymes do their job inside the cell. They are called intracellular enzymes

Question 15

Factors affecting enzyme controlled reactions

1. Explain temperature

Answer 15

At low temperature the enzyme and substrate molecules have less kinetic energy. Since they are moving slowly the rate of collisions between them is reduced. Therefore little product is produced.

As temperature increase so does rate of reaction as there is more kinetic energy so they move faster creating more collisions leading to more reactions so more product is formed.

Enzymes have an optimum temperature for must this is 37*c (body temp) there are maximum reactions so maximum product is produced.

If temperature is above optimum, chemical bonds holding the enzymes structure together break. This causes irreversible change to the active site. The enzyme is denatured. The substrate no longer fits the active site so fewer products are produced.

Question 16

Factors affecting enzyme controlled reactions

2. Explain pH

Answer 16

Each enzyme has an optimum pH. For most it is close to neutrality (pH 7 which is found in most cells) Pepsin (a protease) has a very different pH, the digestive enzyme secreted into the stomach where conditions are very acidic.

Enzymes operate over a very narrow pH range, if not close to optimum pH they become denatured.

Question 17

Factors affecting enzyme controlled reactions

3 explain enzyme concentration

Answer 17

At low enzyme concentration there are insufficient available active sites for collisions. Therefore rate of reaction is low & few products are formed

At high enzyme concentration the rate of reaction increases as their are more available active sites for collisions. However this applies to a limit. At very high enzyme concentration rate of reaction levels off as there are not enough substrate molecules

Question 18

In the situation of many available active sites and not enough substrate molecules how could you further increase rate of reaction?

Answer 18

Increase the concentration of the substrate