Bioenergetics simple questions

See attached

Exercise 2

The activity of isocitrate dehydrogenase from kidney was assayed and the data obtained are presented in figure 1.

Figure 1. Isocitrate dehydrogenase; variation of rate of reaction with isocitrate concentration.

Questions (exercise 2):
a) Compare the shapes of the curves for the rate of reaction against L-isocitrate concentration in the presence and absence of ADP. Explain the effect of ADP and the underlying mechanism.
(4 marks)

b) Explain the metabolic significance of the effect of ADP on the activity of isocitrate dehydrogenase.
(2 marks)

c) Name any other intracellular molecules that normally regulate the activity of this enzyme and state whether they are activators or inhibitors and through which mechanism.
(2 marks)

Exercise 3

The data in the table below represents part of the laboratory analysis for a five day old female child rushed into hospital unconscious.

Table 2.Laboratory analysis.

Analyte

Patient Value

Reference Values

Blood

Leucine

2470 mol/L

40-158

Isoleucine

850 mol/L

13-81

Allo-Isoleucine

127 mol/L

<5 Valine 970 mol/L 85-334 Glutamate 72 mol/L 11-79 Glutamine 806 mol/L 475-746 Phenylalanine 60 mol/L 34-101 alpha-ketoisocaproate 876 mol/L 24-44 Urine Leucine 1559 mol/g creatinine 78-195 Isoleucine 463 mol/g creatinine 125-390 Valine 415 mol/g creatinine 113-369 alpha-ketoisocaproate 287 mol/g creatinine <15 Questions (exercise 3): d) What condition is the child suffering from? Explain your ‘diagnosis’ in terms of each of the data in the table. (5 marks) i) What is the underlying [biochemical] cause of the condition the patient is suffering from? Include details of any relevant enzymatic reactions/pathways. (3 marks) j) What ‘unusual’ metabolite, not listed above, would you also expect to be found in the urine of the child? Explain how this metabolite might be related to the diagnosed disorder. (3 marks) k) Once stabilised the child was maintained on dietary therapy. Outline what form the dietary therapy would take, including any ‘supplements’ that may be added to the basic diet as required. [please note the patients age] (4 marks) Exercise 4 Acetyl-CoA carboxylase is a key regulatory enzyme in fatty acid synthesis. Early studies on the molecular properties of this enzyme purified from avian liver produced the data given in table 3. Table 3. Molecular properties of avian acetyl-CoA carboxylase Treatments Sedimentation coefficient (S) Molecular mass (kDa) Catalytic activity (arbitrary units) 10 mM citrate 55-59 4000-8000 35 0.5M NaCl, pH8-9 13.1 410 2.5 l) Explain the results shown in table 3 in terms of the molecular structure of acetyl-CoA carboxylase and comment on their apparent physiological significance. (4 marks) m) Which cellular compartment would you expect the acetyl-CoA carboxylase activity to have been observed in and why? (2 marks) 1