Biological Reactions Regulated By Enzymes- Unit 1.4

Question 1

Where do the enzyme and substrate combine?

Answer 1

The active site

Question 2

What protein structure do all enzymes have?

Answer 2

Tertiary in 3D spherical globular shape

Question 3

Anabolic vs catabolic enzymes.

Answer 3

Anabolic- build larger products from smaller substrates.

Catabolic- break large substrates into smaller products.

Question 4

What is the function of a lysozyme?

Answer 4

To destroy pathogenic bacteria by breaking down their cell walls by breaking glycosidic bonds between the amino sugars.

Question 5

How is a substrate held in place when attached to a lysozyme?

Answer 5

Hydrogen and ionic bonds

Question 6

What is the lock and key hypothesis?

Answer 6

There is an exact fit between substrate and active site of an enzyme.

Question 7

What is the induced fit hypothesis?

Answer 7

Active site is not exactly the right shape to begin with. The substrate changes the shape of the active site to fit the substrate perfectly. (complementary shape)

Question 8

Name 2 enzyme properties.

Answer 8

1. Specific- each enzyme will catalyse only one particular reaction.
2. Very efficient & have a high turnover number. (can convert many molecules of substrate into product per unit)

Question 9

What is activation energy and what is it used for?

Answer 9

Energy needed to start chemical reactions by breaking chemical bonds inside molecules.

Question 10

Do body enzymes increase or decrease the activation energy of a reaction?

Answer 10

The lower it, reducing input of energy needed to allow reactions to take place, meaning they can take place at lower temperatures.

Question 11

What are the factors that can affect enzyme activity? (4)

Answer 11

Changing:

1. Temperature
2. pH
3. Substrate concentration
4. Enzyme concentration

Question 12

What happens when temperature is increased?

Answer 12

1. Gives molecules greater kinetic energy as enzyme & substrates move around quicker, increasing chance of collision.
2. Increase rate of reaction.

Question 13

For each 10°C rise…

Answer 13

Rate of reaction doubles

general rule

Question 14

How do enzymes denature?

Answer 14

Vibrations break hydrogen bonds within the active site, causing shape to change.

Question 15

What is the turn-over number?

Answer 15

The number of substrate molecules that one enzyme molecule can turn into products in a given time.

Question 16

What is a limiting factor?

Answer 16

A factor is limiting when an increase in its value causes an increase in rate of reaction.

Question 17

What is an enzyme inhibitor? (2)

Answer 17

1. Any substance which decreases rate of an enzyme catalysed reaction or stops it.
2. Can be competitive of non-competitive.

Question 18

Describe competitive inhibitors. (2)

Answer 18

• Structurally similar to substrate.

* Can fit into active site, preventing enzyme-substrate complex forming.

Question 19

What effect will increasing substrate concentration have on a competitive inhibitor?

Answer 19

Decreasing likeliness of inhibitor colliding with enzyme as less likely to bind with active site.

Question 20

Describe non-competitive inhibitors. (2)

Answer 20

• Do not bind to active site, but does anywhere else.

* Alters overall shape or enzyme, including active site so that substrates cannot fit onto it.

Question 21

What effect will increasing substrate concentration have on a non-competitive inhibitor?

Answer 21

Will not increase rate of reaction as substrate can no longer fit into enzymes active site.

Question 22

What are immobilised enzymes?

Answer 22

Fixed, bound or trapped on an inert matrix. (prevent them from moving, reducing frequency of successful collisions)

Question 23

Name advantages of using immobilised enzymes. (7)

Answer 23

1. Enzyme does not contaminate product.
2. Can be recovered & reused.
3. Only small quantity needed.
4. Great stability.
5. Denature at higher temperatures.
6. Catalyse reactions over wider range of pH.
7. Greater control over process.

Question 24

What are biosensors?

Answer 24

Can detect biologically important molecules rapidly, even at low concentrations.
e.g. Used to measure blood glucose in diabetics.

Question 25

How do biosensors work?

Answer 25

Use immobilised enzymes on a gel membrane to detect chemical changes and turns it into an electrical signal.