Carbohydrates Flashcards Preview

Science for Medicine > Carbohydrates > Flashcards

Flashcards in Carbohydrates Deck (30):
1

Give the major monosaccharides in the diet

- glucose
- galactose
- fructose

2

Give the major disaccharides in the diet

- maltose
- sucrose
- lactose

3

Glucokinase and hexokinase are

isoenzymes

4

Isoenzymes

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

5

Glucokinase is found in the

liver

6

Glucokinase has a _

high Vmax and high Km

7

Glucokinase will only pick up glucose when

the concentration is high e.g. after a meal

8

The high Vmax of glucokinase allows it to

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

9

Hexokinase has a _

low Vmax and low Km

10

Hexokinase can bind to glucose even at low concentrations
True or false?

True

11

Low Vmax means that the tissues that hexokinase is found in

are quickly satisfied

12

Glycogen is a polymer of

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

13

Glycogen does not form directly from

glucose subunits

14

Glycogen starts by

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

15

Glycogen synthase takes over and

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

16

During degradation, glucose subunits are

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

17

Glycolysis is

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

18

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

2 ATP molecules
2 NADH molecules
2 pyruvate molecules

19

Describe the functions of the lactate dehydrogenase

Used in converting lactate into pyruvate using NAD+ during gluconeogenesis

20

Describe the functions of pyruvate dehydrogenase

Converts pyruvate to acetyl coenzyme A

21

Describe the fate of blood lactate

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

22

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

Gluconeogenesis

23

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

The Cori cycle

24

How many of the glycolytic reactions are reversible?

7 out of 10

25

Galactose joins the glycolysis cycle through conversion to

glucose-1-phosphate by UDP

26

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

fructose-1-phosphate

glyceraldehyde

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

27

The glycolysis cycle produces ___ and also metabolises ___

NADPH and pentose sugars needed for nucleic acid synthesis

the small amount of pentose sugars in the diet

28

What are the two phases of the glycolysis cycle?

- oxidative, irreversible part
- reversible, non-oxidative part

29

What happens in the oxidative phase of the glycolysis cycle?

- NADPH generated
- G-6-P converted into a pentose phosphate

30

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

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