Enzymes

Question 1

What is an enzyme?

Answer 1

a globular protein that catalyses metabolic reactions

Question 2

What are two types of enzymes?

Answer 2

intracellular and extracellular

Question 3

What is an active site?

Answer 3

an active site is the place on the enzyme where the substrate fits

Question 4

What is an enzyme-substrate complex?

Answer 4

the bonded enzyme and substrate by temporary hydrogen bonds between the R groups of their amino acids

Question 5

What effect does an enzyme have on activation energy?

Answer 5

lowers the energy needed to start a reaction

Question 6

What is enzyme specificity?

Answer 6

each enzyme is specific for its complementary substrate

Question 7

What is the lock-and-key hypothesis?

Answer 7

the shape of the substrate is complementary to the active site of the enzyme, and it fits into the enzyme like a lock in a key

Question 8

What is the induced fit hypothesis?

Answer 8

the enzyme and substrate are not exactly complementary so the enzyme changes shape slightly to allow the substrate to fit better

Question 9

How can the progress of a reaction be measured?

Answer 9

the amount of product produced or substrate disappeared, plotted on a graph showing rate of reaction

Question 10

What factors affect the rate of enzyme-catalysed reactions?

Answer 10

• temperature
• PH
• enzyme concentration
• substrate concentration
• inhibitor concentration

Question 11

How does temperature affect the rate of reaction?

Answer 11

increasing temperature increases rate of reaction, too high temperature causes bonds to break and the enzyme to denature, slowing rate of reaction

Question 12

How do PH changes affect the rate of reaction?

Answer 12

a more acidic or basic PH interferes with ionic bonds and causes and enzymes to denature, slowing rate of reaction

Question 13

How does enzyme concentration affect the rate of reaction?

Answer 13

higher enzyme concentration increases initial rate of reaction

Question 14

How does substrate concentration affect the rate of reaction?

Answer 14

higher substrate concentration increases initial rate of reaction

Question 15

How does inhibitor concentration affect the rate of reaction?

Answer 15

higher inhibitor concentration slows rate of reaction

Question 16

What are competitive reversible inhibitors?

Answer 16

inhibit enzyme activity by fitting into active site

Question 17

What are non-competitive reversible inhibitors?

Answer 17

inhibit enzyme activity by attaching somewhere else on the enzyme molecule, help with end-product inhibition

Question 18

What is the affect of immobilising an enzyme in alginate?

Answer 18

enzymes can be reused and do not mix with the product, they are also more tolerant to PH and temperature changes

Question 19

What is Vmax?

Answer 19

velocity max, the maximum rate of reaction, where all enzymes are saturated with substrate

Question 20

What is the Michaelis-Menten (Km) constant?

Answer 20

half of Vmax, when half the active sites of enzymes are occupied with substrate, the lower the Km constant, the higher the enzyme affinity

Question 21

What is initial rate of reaction?

Answer 21

the rate of reaction is always fastest at the beginning, calculated by curve gradient or by reading off the graph

Question 22

What is denaturation?

Answer 22

when an enzymes loses shape and activity

Question 23

How do you calculate Vmax from a double-reciprocal plot?

Answer 23

1/Vmax is the point where the line meets the y-axis (where 1/S), from there Vmax is calculated

Question 24

How do you calculate Km from a double-reciprocal plot?

Answer 24

-1/Km is where the line of the graph intersects the x-axis, from there Km is calculated

Question 25

What is a double-reciprocal plot?

Answer 25

the inverse of velocity plotted against the inverse of substrate concentration