Q: Which of the following equations correctly represents the reaction catalyzed by galactokinase?

$$\mathrm{Galactose} + \mathrm{ATP} \rightarrow \mathrm{Galactose\ 1\text{-}phosphate} + \mathrm{ADP}$$

Question 1

Which enzyme is responsible for the phosphorylation of fructose in the liver, kidneys, and small intestine, allowing it to enter metabolic pathways?

Accepted Answer

Fructokinase

Question 2

A patient presents with hypoglycemia, vomiting, and jaundice shortly after ingesting fruit juice. Laboratory tests reveal accumulation of fructose 1-phosphate in the liver. Which enzyme deficiency is most likely responsible for these symptoms?

Accepted Answer

Aldolase B

Question 3

Which of the following statements about fructose metabolism is CORRECT?

Accepted Answer

Fructose transport into cells is insulin-independent.

Question 4

What are the products of the aldolase B-catalyzed cleavage of fructose 1-phosphate?

Accepted Answer

Dihydroxyacetone phosphate (DHAP) and glyceraldehyde

Question 5

Which metabolic disorder is characterized by the accumulation of galactose 1-phosphate and galactitol, leading to liver damage and cataracts in infants?

Accepted Answer

Classic galactosemia

Question 6

Which enzyme catalyzes the conversion of glucose to sorbitol, a process that can contribute to diabetic complications?

Accepted Answer

Aldose reductase

Question 7

In the polyol pathway, which tissue is most likely to suffer damage due to sorbitol accumulation in uncontrolled diabetes?

Accepted Answer

Peripheral nerves

Question 8

Which of the following equations correctly represents the reaction catalyzed by galactokinase?

Accepted Answer

$$\mathrm{Galactose} + \mathrm{ATP} ightarrow \mathrm{Galactose\ 1	ext{-}phosphate} + \mathrm{ADP}$$

Question 9

Which enzyme deficiency leads to essential fructosuria, a benign condition characterized by the presence of fructose in urine?

Accepted Answer

Fructokinase

Question 10

Which of the following is TRUE regarding the synthesis of lactose in the mammary gland?

Accepted Answer

Lactose synthase consists of two subunits, protein A and protein B.

Question 11

Which of the following reactions is catalyzed by aldose reductase in the context of diabetic complications?

Accepted Answer

$$\mathrm{Glucose} + \mathrm{NADPH} \rightarrow \mathrm{Sorbitol} + \mathrm{NADP}^+$$

Question 12

Which of the following best explains why hyperglycemia can lead to cataracts in diabetic patients?

Accepted Answer

Excess glucose is converted to sorbitol, which accumulates and causes osmotic damage.

Question 13

Which of the following is a direct product of the reaction catalyzed by galactose 1-phosphate uridylyltransferase (GALT)?

Accepted Answer

UDP-galactose

Question 14

Which of the following equations represents the reaction catalyzed by sorbitol dehydrogenase?

Accepted Answer

$$\mathrm{Sorbitol} + \mathrm{NAD}^+ \rightarrow \mathrm{Fructose} + \mathrm{NADH}$$

Question 15

Which of the following statements about mannose metabolism is CORRECT?

Accepted Answer

Mannose is converted to mannose 6-phosphate by hexokinase.

Question 16

A newborn is found to have elevated galactose in the blood and urine, and develops cataracts. Which enzyme is most likely deficient?

Accepted Answer

Galactokinase

Question 17

Which of the following is a consequence of aldolase B deficiency?

Accepted Answer

Hereditary fructose intolerance with hypoglycemia and liver failure

Question 18

Which of the following best describes the role of UDP-galactose in biosynthetic reactions?

Accepted Answer

It serves as a donor of galactose units for the synthesis of lactose, glycoproteins, and glycolipids.

Monosaccharide and Disaccharide Metabolism: Biochemistry Study Notes

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