Lecture 7 - Enzymes

Question 1

What is an enzyme

Answer 1

A powerful and highly specific biological catalyst

A catalyst increases the rate of a chemical transformation

*Enzymes function to lower the activation energy by facilitating the formation of the transition state

Question 2

What are proteases

Answer 2

Proteases are enzymes that cleave peptide bonds

Question 3

Why do enzymes have substrate specificity?

Answer 3

Enzyme specificity is due to the precise interaction of the substrate and enzyme

This precision is due to the intricate three-dimensional structure of the enzyme

Question 4

What are the major classes of enzymes

Answer 4

Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligase

(Slide 9)

Question 5

How do enzymes work

Answer 5

A chemical reaction of substrate S to form product P goes through a transition state S‡that has a higher free energy than either S or P

Enzymes have evolved to lower the activation energy of the transition state and therefore increase the rate of the reaction

Question 6

What is an exergonic reaction

Answer 6

Reaction is spontaneous
(google it)

Question 7

What is an endergonic reaction

Answer 7

Reaction isnt spontaneous
(google it)

Question 8

In equilibrium position, why is the concentration the same of reactants and products, if you start with varying amounts of R or P? eg. 100% R, 0% P ORA

Answer 8

equilibrium position is a function only of the free energy difference (ΔG)

Catalysts alter only the reaction rate and not the equilibrium position

Question 9

What is binding energy

Answer 9

Formation of each weak interaction in the ES complex is accompanied by release of a small amount of free energy that stabilizes the interaction

The energy derived from enzyme-substrate interaction

Question 10

What is a key bit of evidence against the lock and key model

Answer 10

Enzymes are complimentary to the transition state not the substrate

Question 11

Rearrangement of covalent bonds

Answer 11

Slide 20

Question 12

Principles of Biochemistry, Lehninger, 7th Edition, p216-217

Question 13

What is Entropy Reduction

Answer 13

an enzyme holds reactants (substrates) close together in the right orientation for the reaction, which reduces the reliance on random collisions

Question 14

How does Desolation of the substrate occur

Answer 14

Formation of weak bonds between substrate and enzyme

Question 15

What is substrate distortion

Answer 15

Binding energy in the transition state compensates for thermodynamically unfavourable free-energy changes

Question 16

What is induced fit

Answer 16

The enzyme undergoes a change in conformation upon substrate binding, which brings specific functional groups on the enzyme into the proper position to catalyse the reaction

Question 17

What are some types of enzyme specificity

Answer 17

Geometric and stereospecificity

Question 18

What are metlloproteases

Answer 18

family of enzymes that require metal ions, such as Zn2+, for activity