14. Carbohydrates

Question 1

What are the 4 possible fates of glucose?

Answer 1

1. Metabolised to produce energy (ATP)
2. Converted to glycogen for storage
3. Synthesis of cellular components
4. Converted to fat for storage

Question 2

What happens if blood glucose is below 3mM?

Answer 2

confusion
coma

should be constant 5mM

Question 3

What happens if blood glucose is above 8mM?

Answer 3

long term vascular damage due to protein glycation.

Question 4

Can glycolysis take place in anaerobic conditions?

Answer 4

Yes

Question 5

What is the preparative phase of glycolysis?

Answer 5

Glucose > Fructose 1,6 bisphosphate.

Uses ATP.

Question 6

What is the generative phase of glycolysis?

Answer 6

Fructose 1,6 bisphosphate > 2 Pyruvates.

Generates ATP + NADH.

Question 7

Identify the 3 monosaccharides that are metabolised.

Answer 7

Glucose - (starch + glycogen)
Fructose - (sucrose)
Galactose - (lactose)

Question 8

How does the energy yield of aerobic glycolysis differ from anaerobic glycolysis?

Answer 8

Aerobic = 5-7 ATP (NADH can undergo oxidative phosphorylation)

Anaerobic = 2 ATP

Question 9

How many molecules of ATP is yielded from complete oxidation of glucose via the Krebs cycle?

Answer 9

30-32 ATP

Question 10

Glucose is not able to leave the cell once it is phosphorylated.
True or False?

Answer 10

TRUE

Question 11

What are the key control points (reactions) of glycolysis and their enzymes?

Answer 11

1. Hexokinase/glucokinase
   glucose > glucose-6-phosphate
2. Phosphofructokinase
   fructose-6-phosphate > fructose 1,6 bisphosphate
3. pyruvate kinase
   phosphoenolpyruvate > pyruvate

Question 12

Why might a high lactate level be indicative of cancer?

How would a PET scan confirm this?

Answer 12

Tumour cells absorb glucose more rapidly than normal cells, but they use anaerobic glycolysis despite having oxygen present.
This leads to high lactate production.

A tumour in a PET scan would show increased glucose uptake and glycolysis.

Question 13

Where is glycogen mainly found?

Answer 13

liver + skeletal muscle

Question 14

During what period of the day is liver glycogen level at its lowest?

Answer 14

Falls significantly at night, at the lowest in the early morning.

Question 15

What is the name of the primer needed in glycogen synthesis?

Answer 15

Glycogenin

Question 16

What is the key control enzyme for glycogen synthesis and what does it do?

Answer 16

Glycogen synthase

elongates glycogen and adds branching.

Question 17

What is the key control enzyme for glycogen breakdown (glycogenolysis)?

Answer 17

Glycogen phosphorylase

Question 18

Glucose-6-phosphate cannot be converted to glucose in the liver and kidney.
True or False?

Answer 18

FALSE

only glucose-6-phosphate is converted to glucose in kidney and liver.

Question 19

What effect does athletic training have on muscle?

Answer 19

↑ mitochondria

↑ muscle glycogen content

Question 20

What effect does ↑ insulin have on glycolysis?

Answer 20

Stimulates glycolysis

Question 21

What effect does ↑ glucagon have on glycolysis?

Answer 21

Inhibits glycolysis

Question 22

What are fatty acids used for?

Answer 22

1. Storage as triglycerides

2. Synthesis other lipids e.g. membranes

Question 23

Where does fatty acid synthesis occur?

Answer 23

In the cytosol of:

Liver
Adipose tissue
Breast tissue (during lactation)

Question 24

What is the key control enzyme for fatty acid synthesis?

Answer 24

Acetyle CoA carboxylase

acetyle CoA > malonyl CoA