Question 1

Which of the following best explains why humans can digest starch but not cellulose, even though both are polymers of glucose?

Accepted Answer

Starch contains α-glucose monomers with glycosidic linkages that human enzymes can hydrolyze, while cellulose contains β-glucose monomers with linkages that human enzymes cannot break.

Question 2

A biochemist isolates a lipid sample and finds that its fatty acid tails contain multiple double bonds. Which of the following statements is most accurate regarding this lipid?

Accepted Answer

It is an unsaturated fatty acid and will likely be liquid at room temperature due to kinks in the hydrocarbon chains preventing tight packing.

Question 3

Which of the following best describes the process of dehydration synthesis?

Accepted Answer

A water molecule is removed to form a covalent bond between monomers.

Question 4

Which of the following is a direct result of the amphipathic nature of phospholipids in an aqueous environment?

Accepted Answer

Phospholipids spontaneously arrange into bilayers with hydrophobic tails facing inward and hydrophilic heads facing outward.

Question 5

Which level(s) of protein structure are most likely to remain intact after thermal denaturation at 80°C?

Accepted Answer

Primary structure, because peptide bonds are covalent and more resistant to heat than non-covalent interactions.

Question 6

A mutation causes a polar amino acid in a protein to be replaced by a nonpolar one. Which of the following is the most likely consequence for a water-soluble globular protein?

Accepted Answer

The nonpolar amino acid will likely be buried in the protein's interior, potentially disrupting folding and function.

Question 7

Which of the following best describes the Central Dogma of molecular biology?

Accepted Answer

Genetic information flows from DNA to RNA to protein.

Question 8

A sample is found to have the empirical formula $$\mathrm{C}_n\mathrm{H}_{2n}\mathrm{O}_n. To $$which class of macromolecules does it most likely belong?

Accepted Answer

Carbohydrate

Question 9

Which of the following pairs contains only pyrimidine bases found in nucleic acids?

Accepted Answer

Cytosine and Uracil

Question 10

Which of the following bonds or interactions is primarily responsible for maintaining the secondary structure (α-helix and β-sheet) of proteins?

Accepted Answer

Hydrogen bonds between backbone atoms

Question 11

A patient is diagnosed with a genetic disorder where a single amino acid substitution (valine for glutamic acid) occurs in hemoglobin. What is the most immediate effect on the protein's structure?

Accepted Answer

The primary structure changes, which alters hydrophobic R-group interactions, leading to abnormal quaternary aggregation.

Question 12

Which of the following best explains why cellulose acts as 'insoluble fiber' in the human diet?

Accepted Answer

Cellulose contains β-1,4 glycosidic linkages that human digestive enzymes cannot hydrolyze, making it insoluble and unabsorbable.

Question 13

Which of the following is NOT a component of a nucleotide?

Accepted Answer

A carboxyl group

Question 14

Which of the following statements correctly compares DNA and RNA?

Accepted Answer

DNA contains deoxyribose and thymine, while RNA contains ribose and uracil.

Question 15

Which of the following best describes what happens to the primary structure of a protein when it is heated to 80°C?

Accepted Answer

The primary structure remains intact because peptide bonds are not broken by heat alone.

Question 16

Which of the following scenarios would most likely result in the breakdown of the primary structure of a protein?

Accepted Answer

Treatment with a digestive protease enzyme, which hydrolyzes peptide bonds.

Question 17

Which of the following best explains why unsaturated fats are typically liquid at room temperature?

Accepted Answer

The presence of double bonds introduces kinks in the fatty acid chains, preventing tight packing.

Question 18

Which of the following correctly matches the protein structural level with the type of bond or interaction that stabilizes it?

Accepted Answer

Primary structure — peptide bonds

Question 19

A scientist observes that a protein maintains its primary structure but loses its catalytic activity after being heated. Which of the following best explains this observation?

Accepted Answer

Heat disrupts secondary, tertiary, and quaternary structures, but peptide bonds (primary structure) remain intact.

AP Biology Unit 1: Macromolecules & Structure-Function Relationships – Guided Study

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