Enzymes

Question 1

What do enzymes act as?

Answer 1

They act as biological catalysts

Question 2

What is the function of enzymes?

Answer 2

They increase the rate of reaction by reducing the activation energy needed for the reaction to occur. They are unchanged at the end of the reaction

Question 3

What type of protein are enzymes?

Answer 3

Globular proteins

Question 4

Name of enzymes that act outside the cell and name of enzyme that works inside the cell

Answer 4

Extracellular and intracellular enzymes

Question 5

Briefly describe the lock and key hypothesis

Answer 5

An enzymes active site is highly complementary to its substrate and is rigid and fixed

Question 6

What is the lock and key in the lock and key hypothesis?

Answer 6

Key - substrate
Lock - enzyme

Question 7

Briefly describe the induced fit theory

Answer 7

The active site of the enzyme is flexible and may change slightly to fit the substrate

Question 8

What does the rate at which the reaction occurs depend on? (2)

Answer 8

1. How many enzymes molecules there are
2. The speed at which the enzyme can convert the substrate into product

Question 9

How does an increase in temperature affect the enzyme activity?

Answer 9

Raising the temperature often increases the rate of reaction because molecules have gained kinetic energy and so move faster and are more likely to collide with each other

Question 10

What happens to enzyme activity after optimum temperature is exceeded?

Answer 10

The hydrogen bonds and hydrophobic interactions break so the active site loses its shape and is denatured. Enzyme activity drops

Question 11

What does a rise of 10ºC cause?

Answer 11

Approximately doubles rate of reaction

Question 12

How does pH affect the enzyme?

Answer 12

The pH affects the ionic bonds holding the enzymes shape and may also affect the R groups in the active site which forms temporary bonds with the substrate

Question 13

What are buffer solutions?

Answer 13

Buffer solutions have a specific pH and maintain that pH even if the reaction taking place could cause the pH to change

Question 14

How does enzyme concentration affect enzyme activity?

Answer 14

Provided that plenty of substrate is available, the more enzymes the greater the enzyme activity

Question 15

How does substrate concentration affect enzyme activity?

Answer 15

The initial rate of reaction increases. However if you keep increasing substrate concentration, keeping enzyme concentration constant, there comes a point where every active site is full. Enzymes are working at maximum velocity

Question 16

What is the Michaelis - Menten constant Km?

Answer 16

It is the substrate concentration that sustains half maximum velocity

Question 17

What does Km meausre?

Answer 17

It measures the degree of affinity of an enzyme for the substrate. The smaller the value, the higher the affinity

Question 18

How do competitive inhibitors function?

Answer 18

They have a similar shape to the substrate and enter the enzymes the active site thus inhibiting the enzymes function

Question 19

Why are competitive inhibitors known as reversible?

Answer 19

It can be reversed by increasing the concentration of the substrate

Question 20

How do non-competitive inhibitors function?

Answer 20

The inhibitor molecules bind to an alternative site of the enzyme not the active site. It affects the hydrogen bonds and hydrophobic interactions holding the enzymes in shape, thus changing the active sites shape

Question 21

What effect does increasing the substrate concentration have when non-competitive inhibitors are present?

Answer 21

Has no effect on the inhibition

Question 22

What is one way to decrease the cost of using enzymes?

Answer 22

Use immobilised enzymes

Question 23

What are immobilised enzymes?

Answer 23

Immobilised enzymes are fixed in some way to prevent them from diffusing freely in a solution

Question 24

What are the advantages of using immobilised enzymes?

Answer 24

1) They are more tolerant to of temperature and pH changes than enzymes in solutions

Question 25

Why are immobilised enzymes more tolerant to temperature and pH?

Answer 25

Molecules are held firmly in shape by the alignate in which they are embedded, so they do not denature easily. It may also be because they are not fully exposed to the temperature or pH changes