Enzymes

Question 1

What is significant about enzymes being globular proteins?

Answer 1

It means they are generally soluble

Question 2

What is a cofactor?

Answer 2

Non-protein component needed by the enzyme to work

Question 3

What is a coenzyme?

Answer 3

Complex organic molecule

Takes part in the reaction but is not the enzyme

Question 4

Coenzymes are usually produced from…

Answer 4

Vitamins

Question 5

Define a prosthetic group.

Answer 5

Non-protein group covalently bonded/tightly bound to an enzyme

Question 6

True/False

A prosthetic group is a type of cofactor?

Answer 6

True

PG’s are covalently bonded cofactors

Question 7

What is the Apoenzyme?

Answer 7

Protein component of enzyme that contains a cofactor

Question 8

What is the Holoenzyme?

Answer 8

Whole enzyme

Apoenzyme + any cofactors

Question 9

True or false

There is 6 classes of enzymes based on the location of the enzyme.

Answer 9

False

6 classes based on the type of reaction the enzyme carries out

Question 10

What is a Ligase Enzyme?

Answer 10

Formation of C-C, C-S, C-O, C-N bonds

Bond making/breaking enzyme

Question 11

What is the significance of whether G is positive or negative?

Answer 11

Shows spontaneity

Negative = Spontaneous

Question 12

What is the free energy equation?

Answer 12

/\G = /\H - T*/\S

Question 13

True or false

If E= ‘energy barrier’ is applied to molecule in its ground state, then it will undergo a reaction and change to product.

Answer 13

False :(

It will reach transition state

Can either react to form product, OR revert back

Question 14

How do enzymes reduce activation energy?

Answer 14

Entropy reduction
Desolvation
Induced fit

Question 15

Kachow or Kerchoo

M-M equation assumed that K2 is slower than K1/K-1 so the RDS is:

ES —> E + P

Answer 15

Kachow

Thus rate is proportional to [ES]

Question 16

Give the word definition of the Michaelis constant.

Answer 16

Substrate concentration when initial reaction velocity is half of Vmax

Question 17

Give the numerical definition of the Michaelis constant.

Answer 17

Km = K(-1) / K(1)

Question 18

What does a low Km value indicate?

Answer 18

Enzyme has high affinity for Substrate

Question 19

What does a high Vmax indicate?

Answer 19

Very fast enzyme

Question 20

Describe an enzyme with high Km and high Vmax.

Answer 20

Very fast enzyme that is very bad at grabbing the substrate

Question 21

How are the Lineweaver-Burk plot and Michaelis-Menten equation linked?

Answer 21

L-B is double reciprocal plot of M-M equation

Question 22

Vo = (Vmax*[S]) / (Km + [S])

L-B or M-M?

Answer 22

M-M

Question 23

What is an Isoenzyme?

Answer 23

Two different enzymes that catalyse the same reaction

Question 24

Blow your load or Hit the road

Hexokinase is actually Glucokinase IV.

Answer 24

Hit the road

Glucokinase is a type of hexokinase enzyme

Hexokinase IV

Question 25

Glucokinase is found where?

Answer 25

Liver

Question 26

Describe why Glucokinase having a high Km + Vmax and hexokinase having a low Km + Vmax allows the body to respond to fluctuating [Glc].

Answer 26

- After meal - [Glc] goes up - Hkase already working at Vmax - Gkase able to respond proportionally as extra Glc is left for it

Question 27

What reaction do Glucokinase and Hexokinase catalyse?

Answer 27

Glc + ATP ---> G-6-P + ADP

Question 28

What effect does phosphorylation of Glc have?

Answer 28

Traps Glc Transporters don't recognise G-6-P

Question 29

What experimental method can be used to study isoenzymes or separate complex mixtures of enzymes?

Answer 29

Electrophoresis

Question 30

What is a ternary complex?

Answer 30

When both substrates are in the same complex E + S' + S" <==> ES'S"

Question 31

What is an Allosteric enzyme?

Answer 31

Multiple active sites

Question 32

Gucci gang or itchy wang Cooperative binding: one substrate binding to one active site causes change in the other active sites, allowing more substrates to join

Answer 32

Gucci gang gucci gang gucci gang gucci gang

Question 33

What is the difference between an Un-competitive and a non-competitive inhibitor?

Answer 33

NC - binds onto allosteric site causing change in AS UC - binds on after substrate and prevents interaction from taking place (as efficiently)

Question 34

What is the advantage of transition state analogues?

Answer 34

Easier for enzyme to bind to molecule in transition state shape than normal shape

Question 35

What 2 forms of inhibition can enzymes use to regulate their pathways?

Answer 35

Feedback inhibition | Allosteric inhibition

Question 36

How does feedback inhibition work?

Answer 36

Product of a pathway, or key stage, can inhibit enzyme at start Stops more of the product being made

Question 37

True or false | Allosteric control of enzymes always involves inhibition of the enzyme.

Answer 37

False Effectors can either be activators or inhibitors

Question 38

Why are many enzymes phosphorylated?

Answer 38

Fine tunes enzyme function Adaptation to cellular conditions

Question 39

What is proteolytic cleavage?

Answer 39

Cleavage of inactive proenzyme to form active enzyme

Question 40

Why is proteolytic cleavage useful?

Answer 40

Prevents enzymes damaging cells or generally fucking stuff up Eg: Digestive enzymes

Question 41

What 3 ways are enzyme molecules modulated/controlled?

Answer 41

Proteolytic cleavage Covalent modification (phosphorylation) Allosterically