FREE AP Biology MCQ Question and Answers

Question 1

The small intestine contains villi and microvilli, which aid in reabsorption by

Accepted Answer

increasing the surface area of the small intestine

Answer

Villi are finger-like projections, and microvilli are even smaller projections on the surface of the villi, creating a brush border. This extensive folding dramatically increases the internal surface area of the small intestine. A larger surface area allows for more efficient and rapid absorption of digested nutrients into the bloodstream, maximizing the uptake of essential molecules.

Question 2

In the small intestine, which of the following DOES NOT occur?

Accepted Answer

Pepsin breaks down proteins to amino acids

Answer

Pepsin is a protease enzyme that functions optimally in the highly acidic environment of the stomach, where it begins the digestion of proteins. Once food moves into the small intestine, the pH becomes more alkaline, inactivating pepsin. Protein digestion continues in the small intestine, but it is carried out by other enzymes like trypsin and chymotrypsin, which break proteins into smaller peptides, not directly into amino acids.

Question 3

Which of the following best describes the route a secretory protein will likely take during its synthesis in an animal cell?

Accepted Answer

Ribosome–rough ER–Golgi apparatus–secretory vesicle–plasma membrane

Answer

Secretory proteins are synthesized on ribosomes attached to the rough endoplasmic reticulum (RER). They then enter the RER lumen for folding and modification. From the RER, they travel to the Golgi apparatus for further processing, sorting, and packaging into secretory vesicles. These vesicles then fuse with the plasma membrane, releasing the proteins outside the cell.

Question 4

The following statements about alleles are all true, EXCEPT for

Accepted Answer

an individual with two identical alleles is said to be heterozygous with respect to that gene

Answer

An individual with two identical alleles for a particular gene is described as homozygous, not heterozygous. Heterozygous means having two different alleles for a gene. Alleles are indeed alternative forms of a gene, found at corresponding loci on homologous chromosomes, and a gene can have multiple alleles within a population.

Question 5

Which of the following statements is the LEAST plausible explanation for the seeming low frequency of mutations, despite the fact that mutations happen at a regular and predictable rate?

Accepted Answer

The predictable rate of mutation results in ongoing variability in a gene pool.

Answer

While mutations do occur at a predictable rate and contribute to genetic variability, this statement doesn't explain why the *frequency* of *expressed* mutations might seem low. The other options describe mechanisms that actively reduce the observable impact or prevalence of mutations: undesirable traits are selected against, drastic changes are removed, and recessive mutations may not be expressed. The predictable rate itself doesn't explain *low frequency* in the population, but rather the *source* of new variation.

AP Practice Test

AP Practice Test

FREE AP Biology MCQ Question and Answers