enzymes part1

Question 1

What is an enzyme?

Answer 1

A protein molecule that catalyzes chemical reactions without itself being destroyed or altered

Question 2

How do biological catalysts differ from chemical?

Answer 2

Catalyses very high reaction rates
Shows great reaction specificity
Work in mild temperature/pH conditions
Can be regulated

Question 3

What do oxidoreductases do?

Answer 3

transfer electrons

Question 4

What do transferases do?

Answer 4

group transfers

Question 5

What do hydrolases do?

Answer 5

hydrolysis

Question 6

what do lyases do?

Answer 6

form or add groups to double bonds

Question 7

what do isomerases do?

Answer 7

transfer groups within molecules

Question 8

what do ligases do?

Answer 8

formation of C-C, C-S, C-O and C-N bonds (coupled to ATP cleavage)

Question 9

What is a co factor?

Answer 9

non protein component needed for the reaction

Question 10

What is a co enzyme?

Answer 10

heat-stable substance that can aid enzyme reactions

Question 11

What is an isoenzyme?

Answer 11

enzymes that catalyse the same reaction but vary in structure and other chemical properties

Question 12

What happens in basic reaction (shown as equation)

Answer 12

E + S –ES—-EP—-E + P

Question 13

What do enzymes do to speed up rate of reaction?

Answer 13

lower activation energy

Question 14

How do enzymes lower the activation energy?

Answer 14

Entropy reduction
Enzymes “force” the substrate(s) to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed

Desolvation
Weak bonds between the substrate and enzyme essentially replace most or all of the H-bonds between substrate and aqueous solution

Induced fit
Conformational changes occur in the protein structure when the substrate binds

Question 15

What does V , Vo, V max , [S] , Km stand for ?

Answer 15

V= velocity (rate)
Vo= initial reaction velocity
V max=maximum reaction velocity
[s]= substrate conc
Km=the substrate conc when the reaction is at half the maximum velocity

Question 16

What do Km and Vmax tell us ?

Answer 16

Km – how specific the enzyme is for the substrate

Low value = good fit
High value = poor fit i.e. takes a lot of substrate to get to ½ Vmax

Vmax – how fast a reaction is proceeding when the enzyme is saturated with substrate

Question 17

What is the x intercept of the lineweaver- burk plot?

Answer 17

1/ V max

Question 18

What is y intercept of lineweaver- burk plot?

Answer 18

-1/Km

Question 19

What can affect enzyme reactions?

Answer 19

Enzyme conc – increasing the enzyme concentration will speed up the reaction so long as there is substrate available
Substrate conc – the more substrate that’s available the quicker the enzymes collide and bind with them
Temperature – as the temperature rises the number of collisions between the enzymes and substrates speeds up.
pH – as with temperature it’s important to remember that enzymes are proteins so there are limits to the conditions that they can function at.
Inhibitors – two main forms of inhibition are competitive and non-competitive.

Question 20

Describe competitive inhibition?

Answer 20

Vmax unchanged
Km increases because it takes more substrate to overcome the inhibition

Question 21

Describe non competitive inhibition?