lecture 9 - intro to enzymes

Question 1

How do enzymes catalyse thermodynamically favourable reactions?

Answer 1

By lowering the activation energy required

Question 2

What is required for a reaction to reach a high-energy transition state?

Answer 2

Activation energy supplied

Question 3

What is the activation energy, as read off a reaction progress graph?

Answer 3

The difference in energy between the reactants and the activated complex/transition state

Question 4

How do enzymes influence forward and reverse reactions?

Answer 4

By decreasing activation energy, the forward and reverse reactions are accelerated equally

Question 5

What is the symbol for change in free energy?

Answer 5

ΔG

Question 6

What is the symbol for activation energy?

Answer 6

Ea OR ΔG‡

Question 7

How does ΔG change when an enzyme is introduced to a reaction?

Answer 7

There is no change, only ΔG‡ decreases

Question 8

What type of molecule makes up the majority of enzymes?

Answer 8

Proteins

Question 9

What is the function of glycogen phosphorylase

Answer 9

An enzyme that aids in glycogenolysis - breaking highly branched glycogen into glucose monomers

Question 10

What are the 6 main classes of enzymes?

Answer 10

Oxidoreductants, transferases, hydrolases, lyases, isomerases, ligases

Question 11

What is the role of an oxidoreductant enzyme?

Answer 11

Facilitate redox reactions, with electron transfer

Question 12

What is the role of a transferase enzyme?

Answer 12

Facilitate the transfer of functional groups

Question 13

What is the role of a hydrolase enzyme?

Answer 13

Facilitate the hydrolysis/cleavage of molecules using H2O

Question 14

What is the role of lyase enzymes?

Answer 14

Facilitate the Non-hydrolytic breaking or making of a bond

Question 15

What is the role of isomerase enzymes?

Answer 15

facilitate the transfer of atoms/groups within a molecule to yield an isomeric form

Question 16

What is the function of ligase enzymes?

Answer 16

Join 2 molecules together via the formation of a new bond. this is usually couple to ATP cleavage

Question 17

Ligase enzyme reactions are usually coupled to what reaction?

Answer 17

ATP cleavage, which provides energy

Question 18

What is a cofactor?

Answer 18

A non-protein compound or metal ion that is required for an enzyme’s catalysis

Question 19

What are the 2 classes of cofactor?

Answer 19

Metal ions and coenzymes

Question 20

What are metal ion cofactors?

Answer 20

Lewis acids (electron pair acceptors) that can participate in acid-base catalysis

Question 21

Are metal ions Lewis Acids or Bases?

Answer 21

Lewis Acids (electron pair acceptors)

Question 22

How do metal ions act as cofactors?

Answer 22

They form coordination compounds with precise geometries for positioning reactants exactly where they need to be.

Question 23

What are some common examples of metal ion cofactors?

Answer 23

Mg2+, Zn2+, Fe2+/Fe3+

Question 24

What are coenzymes?

Answer 24

Small organic molecules that act as cofactors/cosubstrates

Question 25

How do coenzymes act as cofactors?

Answer 25

They are carriers of electrons, atoms or functional groups

Question 26

What are coenzymes often derived from?

Answer 26

Vitamins

Question 27

How do enzymes make reactions favourable via reaction coupling?

Answer 27

The coupling of a non-spontaneous and spontaneous reaction can result in an overall spontaneous reaction

Question 28

where do cofactors bind?

Answer 28

the active site

Question 29

What coenzyme facilitates glycogen phosphorylase activity by binding to the active site?

Answer 29

PLP - pyridoxal phosphate