Carbohydrates

Question 1

Give the major monosaccharides in the diet

Answer 1

• glucose
• galactose
• fructose

Question 2

Give the major disaccharides in the diet

Answer 2

• maltose
• sucrose
• lactose

Question 3

Glucokinase and hexokinase are

Answer 3

isoenzymes

Question 4

Isoenzymes

Answer 4

catalyse the same reaction, however their Km’s and Vmax’s differ

Question 5

Glucokinase is found in the

Answer 5

liver

Question 6

Glucokinase has a _

Answer 6

high Vmax and high Km

Question 7

Glucokinase will only pick up glucose when

Answer 7

the concentration is high e.g. after a meal

Question 8

The high Vmax of glucokinase allows it to

Answer 8

pick up glucose quickly so as much glucose as possible is trapped in the liver

Question 9

Hexokinase has a _

Answer 9

low Vmax and low Km

Question 10

Hexokinase can bind to glucose even at low concentrations

True or false?

Answer 10

True

Question 11

Low Vmax means that the tissues that hexokinase is found in

Answer 11

are quickly satisfied

Question 12

Glycogen is a polymer of

Answer 12

glucose (alpha-1 –> 4) linked subunits with (alpha 1 –> 6) branches every 8 to 12 residues

Question 13

Glycogen does not form directly from

Answer 13

glucose subunits

Question 14

Glycogen starts by

Answer 14

covalently binding glucose from UDP-glucose to form chains of approx 8 subunits

Question 15

Glycogen synthase takes over and

Answer 15

extends the chains until they are broken by glycogen branching enzyme to for 1-6 branching points

Question 16

During degradation, glucose subunits are

Answer 16

removed one at a time from the non-reducing end of the branches as G-1-P by phosphorylase

Question 17

Glycolysis is

Answer 17

a metabolic pathway that serves to save some of the potential energy from glucose as ATP via substrate level phosphorylation

Question 18

For every molecule of glucose broken apart, there is a net gain of

Answer 18

2 ATP molecules
2 NADH molecules
2 pyruvate molecules

Question 19

Describe the functions of the lactate dehydrogenase

Answer 19

Used in converting lactate into pyruvate using NAD+ during gluconeogenesis

Question 20

Describe the functions of pyruvate dehydrogenase

Answer 20

Converts pyruvate to acetyl coenzyme A

Question 21

Describe the fate of blood lactate

Answer 21

Lactate is produced via substrate level phosphorylation during exercise when there is not enough O2
Lactate is then made back into glucose in the liver

Question 22

What is the name given to the process of converting lactate back into glucose in the liver?

Answer 22

Gluconeogenesis

Question 23

What is the name given to the cycle between glycolysis in the tissues and gluconeogenesis in the liver?

Answer 23

The Cori cycle

Question 24

How many of the glycolytic reactions are reversible?

Answer 24

7 out of 10

Question 25

Galactose joins the glycolysis cycle through conversion to

Answer 25

glucose-1-phosphate by UDP

Question 26

Fructose joins the glycolysis cycle using ATP to form ___ and then ___ and finally ___

Answer 26

fructose-1-phosphate

glyceraldehyde

glyceraldehyde-3-phosphate (using another molecule of ATP)

Question 27

The glycolysis cycle produces ___ and also metabolises ___

Answer 27

NADPH and pentose sugars needed for nucleic acid synthesis

the small amount of pentose sugars in the diet

Question 28

What are the two phases of the glycolysis cycle?

Answer 28

• oxidative, irreversible part

- reversible, non-oxidative part

Question 29

What happens in the oxidative phase of the glycolysis cycle?

Answer 29

• NADPH generated

- G-6-P converted into a pentose phosphate

Question 30

What happens in the non-oxidative phase of the glycolysis cycle?

Answer 30

• G-6-P and pentose phosphate are interconverted to form lots of 3, 4, 5, 6 and 7 carbon sugars