1. A patient with a hereditary disease gets sick when he eats foods containing s
ID: 66537 • Letter: 1
Question
1. 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? (1 point)
B. Name 3 specific enzymes you think could be responsible. (1 point)
C. Blood tests show the patient has high levels of glyceraldehyde: which enzyme is most likely to be responsible for this disease? (1 point)
2. Describe four metabolic fates of pyruvate. For each fate:
list the compound pyruvate is made into
name the pathway and enzyme involved
tell whether oxygen is present or absent
and tell if any energy or CO2 is used or produced. (4 points)
Explanation / Answer
1.A. Lactose is a disaccharide composed of the monosaccharides D-glucose and D-galactose, joined in a ß-1,4-glycosidic linkage.Sucrose is a disaccharide combination of the monosaccharides glucose and fructose. As the person is getting sick when he eats food containing lactose then he is likely not able to metabolize the monosaccharide Galactose.
B. Enzymes responisble are : galactose 1-phosphate uridylyl transferase enzyme, galactokinase, UDP galactose epimerase.
C.aldehyde reductase is most likely responsible for that disease.
2.four metabolic fates of pyruvate are:
a)Ethanol is formed from pyruvate in yeast and other micro organisms.The first step is decarboxylation of pyruvate which is catalysed by enzyme pyruvate decarboxylase and co enzyme thiamine pyrophospahte.
Oxygen is absent in this process and 2CO2 and 2 ATP is produced.
b)Lactate is formed in a variety of micro organisms by process of lactic acid fermentation. Enzyme is lactate dehydrogenase in presence of limited oxygen. It produces 2ATP.
c) Pyruvate is converted into oxaloacetate under anaerobic conditions by enzyme mitochondrial pyruvate carboxylase which is an ATP required action.
d) Pyruvate is converted into AcetylCoA under aerobic conditions. In mitochondrial matrix it is oxidatively decarbolated by pyruvate dehydrogenase complex. Here, high transfer potential electrons in form of NADH are captured.
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