Chapter 3-Enzymes

Question 1

what is an enzyme?

Answer 1

a biological catalyst which speeds up the rate of reaction

Question 2

what is the energy that is lowered by an enzyme to make the reaction rate faster?

Answer 2

activation energy

Question 3

what are the factors that effect enzyme activity and how do they effect the activity?

Answer 3

1. enzyme concentration - if increased, rate if reaction increases
2. substrate concentration - if increased rate if reaction increases
3. temperature - if increased until optimum temperature, the rate increases. when reached optimum temperature, activity is as high as it can be. after optimum temperature, enzyme gets denatured and rate of reaction starts to decrease.
4. pH - if increased until optimum pH, the rate increases. when reached optimum pH, activity is as high as it can be. after optimum pH, enzyme gets denatured and rate of reaction starts to decrease.

Question 4

describe the lock and key mechanism

Answer 4

lock and key mechanism states that the enzyme is a rigid structure and does not move its shape around or adjust to the substrate.

Question 5

describe the induced fit mechanism

Answer 5

the mechanism of the enzyme that relies on the active site being partially flexible in order to fit the substrate perfectly

Question 6

word for enzymes that function outside cells

Answer 6

extracellular

Question 6

what are competitive inhibitors?

Answer 6

1. compete with the substrate to attach to the active site
2. alter the rate of reaction.
   (reversible)

Question 8

what are non-competitive inhibitors?

Answer 8

1. non-competitive inhibitors attach to the allosteric site
2. changes the shape of the active site so that the substrate can no longer fit into it.
   (irreversible)

Question 9

constant for maximum rate of reaction of enzyme

Answer 9

V max

Question 10

substrate concentration for which the enzyme works at half the maximum rate

Answer 10

Km (Michaelis–Menten constant)

Question 11

advantage of immobilizing enzymes

Answer 11

1. reduces cost
2. enzyme does not denature easily
3. products are not contaminated with the enzyme

Question 12

what is a catalyst?

Answer 12

a substance that increases the rate of reaction without being changed itself

Question 13

how do enzymes lower the activation energy? (2marks)

Answer 13

1. they provide an alternative pathway

2. by bringing the reactants close together

Question 14

name the vesicles in the cell that contain hydrolytic enzymes (1mark)

Answer 14

lysosomes

Question 15

suggest the molecular structure of the enzyme changes during cold denaturation (3marks)

Answer 15

1. loss of tertiary structure because hydrogen/ionic bonds break
2. the shape of enzyme and active site changes therefore substrate cannot fit any longer
3. loss of globular structure