Question

5) Consider an individual who had been undergoing starvation for 4 days. Blood samples and a biopsy of their liver were taken at the start of the starvation period and at the end of starvation. Indicate the likely concentration of metabolites or activity of enzymes, respectively, that molecular analysis would reveal for this person. Indicate if the levels have increased, decreased or remain unchanged over the 4 day period. Provide a reason to justify your conclusion and any potential effect that the molecule/ enzyme would have on a metabolic pathway. (2 marks, 10 x 0.2 marks for each completely correct row).

Note: For the marks to be awarded, the reason has to match the level and use the language described in the unit.

Metabolite, enzyme,        hormonal pathway	Increased, decreased            or stable	Reason         (be concise, do not write more than       1 – 2 sentences each otherwise you will not     receive marks!)
Blood
Glucose (blood)
Glucagon (blood)
Liver cell
Gluconeogenesis
Glyceraldehyde 3                                         phosphate dehydrogenase (GAPDH)
Phospofructokinase-2
Glycogen
Fructose 2,6 bis phosphate
UDP-glucose
Fructose-1,6-bisphosphatase
Oxaloacetate (mitochondrial)

Answer 1

BLOOD Parameters:

Glucose: Decrease

Reason: Available Glucose will be used up for cell survival.

Glucagon: initially Increases

Reason: Since blood glucose is low, glucagon, catabolic hormone, secreted by pancreatic cells to increase the blood glucose level. Glucagon acts on stored glycogen which eventually converts into glucose. It activates gluconeogensis pathway if stored glycogen is used up.

LIVER:

1. Gluconeogenesis: Increase

Reason: Since glycogen will be used up, glucose will be produced from amino acids derived from muscle breakdown.

2. GAPDH: decreases

Reason: Since the enzyme is used for glucose breakdown it wont be used in starvation.

3. Phosphofructokinase 2: decreases

Reason: Since the enzyme is used for glucose breakdown it wont be used in starvation.

4. Glycogen: decrease

Reason: It might have broken down to cope up with increase blood glucose demand.

5. Fructose 2,6 Bis phosphate: Decrease

Reason. It activates glycolysis hence will not be used. In normal condition it stimulates phosphofructosekinase activating glycolysis.

6. UDP-glucose Decrease

Reason: It is precursor for glycogen and adds glucose to pre-exsisting glycogen chain

7. Fructose 1, 6 bis phosphatae- increase

Reaason: It is used in gluconeogenesis pathway to convert Fructose 1, 6, bis phosphate to Fructose 6 phosphate .

8. Oxaloacetate: Decrease

Reason. Since glycolysis is shut down, oxaloacetate is drawn from TCA cycle and used for glucose production.