Enzymes

Question 1

What is a cofactor?

Answer 1

A non protein component needed for activity

Question 2

What is a Coenzyme?

Answer 2

A complex organic molecule such as NADH

Question 3

What is a prosthetic group?

Answer 3

A cofactor bound to the enzyme or tightly associated with it

Question 4

What sort or protein is an enzyme?

Answer 4

Globular

Question 5

How does an enzyme catalyse a reaction?

Answer 5

Lowers activation energy

Accelerates movement towards reaction equilibria

Question 6

How does an enzyme lower activation energy?

Answer 6

Force substrates into correct orientation

Desolvination - forms weak bonds with substrates replacing the substrate-aqueous bonds

Changes shape once substrate is bound creating an induced fit - tigher fit

Question 7

What is the active site complementary to?

Answer 7

The transition state of the substrate - not the actual substrate!

Question 8

What happens if you increase substrate levels?

Answer 8

Faster reaction rate till all enzyme sites are being used - known as Vmax

Question 9

What does the M-M equation state?

Answer 9

Everything after the enzyme-substrate complex is bound is the rate determining step

Question 10

What does a high Km show?

Answer 10

Shows a less stable ES complex so a low affinity

Question 11

What does a low Km show?

Answer 11

Shows a stable ES complex - high affinity

Question 12

What can electrophoresis be used as?

Answer 12

A diagnostic tool to separate complex mixtures of enzymes

Question 13

What is an ordered sequential mechanism?

Answer 13

When the enzyme has two or more substrates and they can only bind and leave in a specific order.

Question 14

What is a random seqeuntial mechanism?

Answer 14

Enzyme has 2 ore more substrates and they can bind and leave in any random order

Question 15

What does pH effect?

Answer 15

Charge of amino acids

Question 16

What is a Competitive inhibitor?

Answer 16

Inhibitor that is similar in shape to substrate and binds non-covalantly to the active site.

This increases Km as affinity for substrate decreases until there is a high conc of substrate to kick out inhibitor.

Question 17

What is a non competitive inhibitor?

Answer 17

Bind non- covalntly allosterically decreasing Vmax but leaving Km unchanged

Question 18

What is an irreversible inhibitor?

Answer 18

Binds to the enzyme covalently and cannot be removed

Question 19

What is feedback inhibition?

Answer 19

If the end product/ key mid-product in a pathway gets too large the product will bind to the enzyme inhibiting it till there is a lower concentration again letting pathway proceed normally. Example of homeostatic control.

Question 20

What is the concerted model of allosteric enzyme kinetics?

Answer 20

Each subunit of an enzyme can have a high or low Km,

All units need to be in the same conformation so flip together.

When one substrate binds, it looks all other to low Km affinity.

Question 21

What is the sequential model?

Answer 21

No flipping between states, one subunit binds which causes only ONE other subunit to change conformation and make binding easier in only that subunit - occurs until all subunits binded.

Question 22

Example of covalent modification?

Answer 22

Phosphorylation of enzyme - makes it more fined tuned

Question 23

What is proteolytic cleavage?

Answer 23

Enzyme is in an inactive state as a proenzyme.

Proenzyme cleaved by proteases giving active enzyme.