Question 1

Which of the following best distinguishes between an aldose and a ketose sugar?

Accepted Answer

Aldoses have a carbonyl group at the end of the carbon chain, while ketoses have it within the chain.

Question 2

Which of the following is a correct statement about the difference between D- and L-carbohydrates?

Accepted Answer

D- and L- forms refer to the configuration around the chiral carbon farthest from the carbonyl group.

Question 3

A patient is diagnosed with lactose intolerance. Which enzyme is most likely deficient, and what type of reaction does it catalyze?

Accepted Answer

Lactase; it catalyzes the hydrolysis of lactose into glucose and galactose: $$\mathrm{C$$_{12}$$H_{22}O$$_{11} + H_2O \rightarrow C_6H_{12}$$O_6 + C_6H$$_{12}$$O_6$$}$

Question 4

Which of the following is NOT a physical property of fatty acids?

Accepted Answer

Ability to form peptide bonds

Question 5

Which statement best explains why unsaturated fatty acids have lower melting points than saturated fatty acids?

Accepted Answer

The presence of double bonds introduces kinks, preventing tight packing of molecules.

Question 6

Which of the following is a function of lipids in biological systems?

Accepted Answer

Energy storage and membrane structure

Question 7

Which of the following amino acids is classified as nonpolar and aliphatic?

Accepted Answer

Leucine

Question 8

A protein is denatured by heating. Which level(s) of protein structure are most likely disrupted?

Accepted Answer

Secondary, tertiary, and quaternary structures

Question 9

Which of the following best describes the peptide bond?

Accepted Answer

It is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another, releasing water: $$\mathrm{R_1$-COOH + R_2$-NH_2$ \rightarrow R_1$-CO-NH-R_2$ + H_2O}$$

Question 10

Which of the following statements about enzyme catalysis is correct?

Accepted Answer

Enzymes lower the activation energy ($$E_a) of a $$reaction without altering the overall $$	riangle G.$$

Question 11

A competitive inhibitor of an enzyme will have which of the following effects on $$V_{max}$$ and $$K_m$$?

Accepted Answer

$$V_{max}$$ remains unchanged, $$K_m$$ increases

Question 12

Which of the following is a correct classification of the enzyme hexokinase?

Accepted Answer

Transferase

Question 13

Which statement best describes the difference between a cofactor and a coenzyme?

Accepted Answer

A cofactor can be inorganic (such as metal ions), while a coenzyme is an organic molecule.

Question 14

Which of the following reactions is catalyzed by a hydrolase enzyme?

Accepted Answer

Cleavage of a peptide bond by addition of water: $$\mathrm{R_1$-CO-NH-R_2$ + H_2O \rightarrow R_1$-COOH + R_2$-NH_2$}$$

Question 15

Which of the following best describes the tertiary structure of a protein?

Accepted Answer

The overall three-dimensional folding of a single polypeptide chain, stabilized by interactions such as hydrophobic interactions, hydrogen bonds, and disulfide bridges.

Question 16

Which of the following is a correct example of an isomerase-catalyzed reaction?

Accepted Answer

Conversion of glucose-6-phosphate to fructose-6-phosphate: $$\mathrm{C_6H_{13}O_9P \rightarrow C_6H_{13}O_9P}$$

Question 17

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is determined by the precise interaction between the enzyme's active site and the substrate.

Question 18

Which of the following best describes the role of chaperone proteins in cells?

Accepted Answer

They assist in the proper folding of other proteins and prevent aggregation.

Question 19

Which of the following is a correct classification of the reaction catalyzed by lactate dehydrogenase?

Accepted Answer

Oxidoreductase

Biochemistry Exam Study Guide: Carbohydrates, Lipids, and Proteins

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