Enzymes, 2.4

Question 1

What are enzymes and what is their role?

Answer 1

Biological catalysts. Speed up metabolic reactions

Question 2

What is the turnover number?

Answer 2

The number of reactions an enzyme can catalyse per second

Question 3

What type of proteins are enzymes?

Answer 3

Globular

Question 4

Why is the structure of an enzyme important?

Answer 4

Determines its function

Question 5

What is substrate?

Answer 5

A molecule on which an enzyme acts

Question 6

What is the active site?

Answer 6

Area on an enzyme which is complementary to the substrate molecule.

Question 7

How can the shape of an active site be altered?

Answer 7

Increase in temperature. Change in pH.

Question 8

What are enzymes inside the cell called?

Answer 8

Intracellular

Question 9

What are enzymes outside the cell called?

Answer 9

Extracellular

Question 10

Describe the function of lactase

Answer 10

Breakdown of milk, sugar and lactose intolerance glucose and galactose. Lactose intolerant = don’t produce lactase.

Question 11

What is the function of catalase?

Answer 11

Breakdown of hydrogen peroxide to water and oxygen. Hydrogen peroxide is toxic but is a by product of some reactions

Question 12

What is a cofactor for?

Answer 12

Addition of a non-protein to an enzyme before they can catalyse

Question 13

What is a prosthetic group?

Answer 13

A cofactor for which is permanently bound - covalent bonds. Part of its 3D shape

Question 14

What is an example of a prosthetic group?

Answer 14

Enzyme carbonic anhydrase - catalysed CO2 and H2O to carbonic acid

Question 15

What are coenzymes?

Answer 15

Organic molecules that bind temporarily transferring a chemical group when required. They are chemically changed after and need to be recycled.

Question 16

Give an example of a coenzyme

Answer 16

B3 - needed for respiration and energy to grow

Question 17

Describe the Lock and Key Hypothesis.

Answer 17

1. Substrate identifies active site of enzyme
2. Substrate fits into the enzymes active site
3. Temporary hydrogen bonds hold them together
4. Substrate is broken into smaller product molecules that leave the active site

Question 18

Describe the Induced Fit Hypothesis..

Answer 18

1. Shape of the active site is complementary to the shape of the substrate
2. Enzyme modules itself around the substrate
3. Intermolecular forces bind
4. Product will be a different shape and will detach

Question 19

What is an advantage of enzymes?

Answer 19

Lower activation energy. When molecules collide they need to collide with sufficient energy to cause a reaction

Question 20

What is the effect of increasing the temperature on enzymes?

Answer 20

Molecules gain energy and move faster, increases the chance of collisions and the energy with which molecules collide. Rate of reaction increases.

Question 21

What is the optimum temperature?

Answer 21

When the rate of reaction is at its maximum. After this the enzyme denatures.

Question 22

Why does an increase in temperature denature an enzyme?

Answer 22

Breaks the weak bonds in the enzyme which hold the tertiary structure together. Active site changes shape. Change is irreversible.

Question 23

What is meant by the temperature coefficient Q10?

Answer 23

Increase in the rate of a process when the temperature rises by 10degrees

Question 24

What is Q10?

Answer 24

Rate of reaction at (T+10) / rate of reaction (T)

Question 25

What does the pH show?

Answer 25

Whether a substance is acid, alkali or neutral.

Question 26

What is a buffer?

Answer 26

Resists changes in pH

Question 27

Why will a change in the pH affect n enzyme?

Answer 27

1. Hydrogen ions causes changes in pH 2. Excess hydrogen ions will interfere with hydrogen bonds and change the shape 3. Less substrate will be able to bind - rate of reaction slowed.

Question 28

What is the optimum pH?

Answer 28

pH at which the rate is at its maximum - after this the enzyme is disrupted

Question 29

Describe the effect of substrate concentration?

Answer 29

1. As substrate concentration increases so does the rate of reaction 2. Can binds to active sites, more complexes formed, more product formed

Question 30

What has happened when the rate of reaction has reached its maximum rate concerning substrate concentration?

Answer 30

All the active sites will be occupied so more substrate will not be able to successfully collide.

Question 31

What is the effect of enzyme concentration?

Answer 31

1. As enzyme concentration increases so does the rate 2. More active sites available, more successful collisions, more product formed 3. At a point there will be no further increase as there will be no more substrate.

Question 32

Why is the initial rate of reaction the fastest?

Answer 32

At the start there is the most substrate - higher chance of collisions

Question 33

Define inhibitor

Answer 33

Substance that slows down the rate of a reaction by affecting the enzyme

Question 34

What are the two types of inhibitor?

Answer 34

Competitive and non-competitive.

Question 35

Describe how competitive inhibitors work?

Answer 35

1. Have a similar shape to enzyme substrate | 2. They compete directly with substrate to form an enzyme-inhibitor complex

Question 36

What does the amount of inhibition depends on in competitive inhibitors?

Answer 36

The concentrations of inhibitor and substrate.

Question 37

How do non-competitive inhibitors work?

Answer 37

1. Binds to the allosteric site and disrupts the tertiary structure 2. Active site is no longer complementary to the substrate 3. Substrate can no longer bind

Question 38

How does the amount on inhibitor effect the rate of reaction in non-competitive inhibition?

Answer 38

More inhibitor the greater the degree of inhibition

Question 39

Why does enzyme activity need to be controlled?

Answer 39

Can be dangerous eg multiple sclerosis.

Question 40

How do we regulate metabolic pathways?

Answer 40

With enzyme inhibition

Question 41

How does enzyme inhibition regulate metabolic pathways?

Answer 41

1. End product acts as a regulator - end product inhibition 2. High amount of product 3. Will bind non-competitively to an enzyme in the pathway 4. When amount of product decreases inhibition ends

Question 42

What is an example of an inhibitor?

Answer 42

Toxins/Venoms - block enzymes. Cyanide - inhibits aerobic respiration. Snake venom - inhibits AChE, causes paralysis.

Question 43

What can we use to stop anti freeze? And why?

Answer 43

Alcohol. Reduces the rate of reaction which breaks down anti freeze. Competitive inhibitor.