Question 1

Which of the following statements best explains why aldoses can act as reducing agents, but ketoses generally cannot?

Accepted Answer

Aldoses contain a terminal aldehyde group that can be oxidized, while ketoses contain a ketone group that cannot be further oxidized under mild conditions.

Question 2

A patient’s urine sample gives a positive Benedict’s test. Which of the following best explains the chemical basis for this result?

Accepted Answer

The urine contains a monosaccharide with a free aldehyde group that reduces Cu$$^{2+} to Cu$_2O.$$

Question 3

How many stereoisomers are possible for a hexose sugar with four chiral centers?

Accepted Answer

$$2^4 = 16$

Question 4

Which of the following pairs are epimers of each other?

Accepted Answer

D-glucose and D-galactose

Question 5

Which of the following best describes the difference between D- and L-glucose?

Accepted Answer

They are enantiomers, differing in the configuration at the chiral center farthest from the carbonyl group.

Question 6

Which enzyme catalyzes the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP) in glycolysis?

Accepted Answer

Triose phosphate isomerase

Question 7

Which of the following best describes the glycosidic linkage in maltose?

Accepted Answer

$$\alpha-1$$,4 linkage between two D-glucose units

Question 8

Which polysaccharide is the primary structural component of plant cell walls and consists of $$\beta-D-$$glucopyranose units linked by $$\beta-1$$,4 glycosidic bonds?

Accepted Answer

Cellulose

Question 9

Which of the following statements about glycogen is FALSE?

Accepted Answer

It is primarily found in plant cell walls.

Question 10

A deficiency in UDP-glucuronosyl transferase (UGT) can lead to which clinical condition due to accumulation of unconjugated bilirubin?

Accepted Answer

Crigler-Najjar syndrome

Question 11

Which of the following is a major function of N-linked glycosylation in glycoproteins?

Accepted Answer

Regulation of protein folding and stability

Question 12

Which of the following best describes the role of the pentose phosphate pathway (PPP)?

Accepted Answer

It generates NADPH and ribose-5-phosphate for biosynthetic reactions.

Question 13

Which enzyme is considered the major rate-limiting step of glycolysis?

Accepted Answer

Phosphofructokinase-1 (PFK-1)

Question 14

Which of the following best explains why glucose is rapidly phosphorylated to glucose-6-phosphate upon entering a cell?

Accepted Answer

To trap glucose inside the cell and prevent its diffusion back out

Question 15

Which of the following is TRUE regarding the regulation of glycogen metabolism in the liver?

Accepted Answer

Glucagon stimulates glycogenolysis and inhibits glycogenesis.

Question 16

Which of the following is a direct result of insulin signaling in skeletal muscle cells?

Accepted Answer

Increased glucose uptake via GLUT transporters

Question 17

Which of the following best describes the effect of epinephrine on glycogen metabolism in skeletal muscle?

Accepted Answer

It activates glycogen phosphorylase, increasing glycogenolysis.

Question 18

Which of the following is a distinguishing feature of proteoglycans compared to glycoproteins?

Accepted Answer

Proteoglycans have a higher carbohydrate content and are mainly found in connective tissue.

Question 19

Which of the following best describes the function of sialic acids in glycoproteins?

Accepted Answer

They impart a negative charge to glycoproteins and are involved in cell recognition.

Carbohydrates: Structure, Functions, and Metabolism (Part 1) – Biochemistry Study Notes

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