A patient with a hereditary disease gets sick when he eats foods containing sucr

Question

A patient with a hereditary disease gets sick when he eats foods containing sucrose, but not when he eats foods containing lactose. You suspect he is unable to metabolize a specific monosaccharide.

A. Which monosaccharide do you think he is unable to metabolize?

B. Name 3 specific enzymes you think could be responsible.

C. Blood tests show the patient has high levels of glyceraldehyde: which enzyme is most likely to be responsible for this disease?

2. Describe four metabolic fates of pyruvate. For each fate: A. list the compound pyruvate is made into B. name the pathway and enzyme involved C. tell whether oxygen is present or absent D. and tell if any energy or CO2 is used or produced.

3. Draw two strands of cellulose lying side by side. Show correct linkages and all hydrogen bonds that are present. You only need to show two residues in each strand.

4. High levels of citrate stimulate the activity of Fructose 1,6 bisphosphate phosphatase but inhibit the activity of phosphofructokinase. Propose an explanation.

Explanation / Answer

I am answering first four questions according to the answering guidelines.

A. He is unable to metabolize fructose.

B. The main enzyme responsible is Aldolase B. However fructokinase also plays a role in pathogenesis of this hereditary disease.

C. Most probably triokinase is responsible for high levels of Glyceraldehyde as it is a transferase which is responsible for conversion of glyceraldehyde to glyceraldehyde-3-phopsphate.

Q2. Following are the metabolic fates of pyruvate:

a) Decarboxylation to acetyl CoA - Pyruvate dehydrigenase - No oxygen present - carbon dioxide produced

b) Carboxylation to oxaloacetate - Pyruvate carboxylase - No oxygen used - Carbon dioxide used

c) Transamination to alanine - Alanine transaminase - No oxygen present - No carbon dioxide used

d) Reduction to lactate - Lactate dehydrogenase - No oxygen present - No carbon dioxide produced

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