Enzymes

Question 1

What is a ribozyme?

Answer 1

A type of RNA that acts as a biological catalyst

Question 2

What is a glycogen storage disease?

Answer 2

An enzyme deficiency that results in failure to break down glycogen

Question 3

What are the 3 reactions (Enzymes) of glycogenolysis?

Answer 3

Glycogen —> Glucose-1-phosphate
(Glycogen phosphorylase)
G-1-P —> Glucose-6-phosphate (Phosphoglucomutase)
G-6-P —> Glucose
(Glucose-6-phosphatase)

Question 4

Which enzyme is affected by Von Gierke’s disease (Glycogen storage disease type I)

Answer 4

Glucose-6-phosphatase

Question 5

What are the symptoms of Von Gierke’s disease?

Answer 5

Hypoglycaemia
Hepatomegaly (Liver swelling)
Mouth ulcers
Skin ulcers
Infection
Bowel inflammation and irritability

Question 6

What is a cofactor?

Answer 6

A metal ion that associates with an enzyme to allow it to perform its function

Question 7

What is a coenzyme?

Answer 7

An organic molecule that associates with an enzyme that helps it to perform its function

Question 8

What name is given to an enzyme when incorporated with a metal cofactor?

Answer 8

A metalloprotein

Question 9

What name is given to an enzyme without a cofactor?

Answer 9

An apoenzyme

Question 10

What name is given to an enzyme with a cofactor?

Answer 10

A haloenzyme

Question 11

What name is given to a tightly bound coenzyme?

Answer 11

A prosthetic group

Question 12

What are isozymes?

Answer 12

Isoforms of an enzyme; they catalyse the same reaction but have different properties and structures

Question 13

What are the 2 subunits of lactate dehydrogenase?

Answer 13

H (heart) and M (muscle)

Question 14

What are the functions of H and M lactate dehydrogenase?

Answer 14

H promotes aerobic metabolism
M promotes anaerobic metabolism

Question 15

What reaction does HLDH promote?

Answer 15

Lactate —> Pyruvate

Question 16

What are the 5 isoforms of LDH?

Answer 16

LDH-1 - 4H subunits
LDH-2 - 3H1M subunits
LDH-3 - 2H2M subunits
LDH-4 - 1H3M subunits
LDH-5 - 4M subunits

Question 17

Which gene codes for the heart subunit?

Answer 17

LDHB

Question 18

What gene codes for the muscle subunit?

Answer 18

LDHA

Question 19

How is the LDHA gene turned on?

Answer 19

Disease causes hypoxia
Hypoxia stimulates the release of hypoxia sensitive transcription factors
These transcription factors bind to the hypoxia response element in the promoter region of LDHA

Question 20

What type of enzyme carries out phosphorylation reactions?

Answer 20

Protein kinases

Question 21

What is the function of phosphorylation?

Answer 21

It can convert an enzyme to either an active or inactive form to regulate the reaction

Question 22

What type of enzyme removes a phosphate group?

Answer 22

Phosphatases

Question 23

What is a zymogen?

Answer 23

An inactive precursor of an enzyme that is irreversibly transformed into an active enzyme

Question 24

What is the zymogen of trypsin?

Answer 24

Trypsinogen

Question 25

What is the zymogen of chymotrypsin?

Answer 25

Chymotryspinogen

Question 26

What converts trypsinogen to trypsin?

Answer 26

Enteropetidase

Question 27

What is Vmax?

Answer 27

The maximum rate at which an enzyme can convert a substrate

Question 28

What is 1/2 Vmax?

Answer 28

Half of the maximum rate at which an enzyme can convert a substrate

Question 29

What is Km

Answer 29

The Michaelis constant:
The substrate concentration at which 1/2 Vmax is reached

Question 30

What are the 3 reactions of an enzyme controlled reaction?

Answer 30

E + S —–> ES (K1)
ES —-> E + S (K-1)
ES —-> E + P (K2)

Question 31

What is the formula for Km using K1, K2 and K-1?

Answer 31

Km = (K-1 + K2) / K1

Question 32

What is the Michaelis-Menten equation of V (velocity of a reaction)?

Answer 32

V = Vmax [S] / Km + [S]