Practice Test for AP Biology - 4 Grade 10 MCQs & solutions - Free

A researcher adds a molecule structurally similar to an enzyme's substrate and observes that increasing the substrate concentration eventually restores the original reaction rate. Which type of inhibition does this describe?

A protein's catalytic activity depends on the precise shape of its active site. When the surrounding pH drops significantly, the protein loses activity. Which level of protein structure is most directly disrupted by this pH change?

A researcher places equal volumes of water and ethanol in sunlight for 30 minutes and records temperature change. Water shows a significantly smaller temperature increase than ethanol. Which property of water best explains this observation?

During digestion, a polysaccharide is broken down into individual monosaccharide units by the addition of water molecules across glycosidic bonds. Which type of chemical reaction is responsible for this breakdown?

A graph plots the rate of glucose transport into a cell against extracellular glucose concentration. The curve rises steeply at low concentrations and then plateaus at high concentrations. When ATP is fully depleted, all transport ceases. Which conclusion is best supported by this data?

Which of the following best distinguishes prokaryotic cells from eukaryotic cells?

A researcher places red blood cells into three solutions and observes the following: cells in Solution 1 lyse, cells in Solution 2 remain unchanged, and cells in Solution 3 shrink. Which of the following correctly identifies the tonicity of each solution relative to the cytoplasm?

Which of the following provides the strongest evidence that mitochondria originated from an ancient endosymbiotic event involving a free-living prokaryote?

A researcher exposes plants to light of different wavelengths and measures the rate of oxygen production. Oxygen production is highest under red and blue light, and minimal under green light. Which conclusion is best supported by this data?

A cell is treated with a drug that specifically blocks electron transfer along the mitochondrial electron transport chain. Which of the following would be the most immediate biochemical consequence?

A graph shows the net rate of CO₂ exchange in a plant over a 24-hour period. During daylight hours, net CO₂ is consumed; during the night, net CO₂ is released. At two points (dawn and dusk), the curve crosses zero. What do these zero-crossing points represent?

During oxidative phosphorylation in cellular respiration, ATP is synthesized as H⁺ ions flow through ATP synthase down their electrochemical gradient. Which process is directly responsible for establishing this H⁺ gradient?

A researcher adds epinephrine to liver cells and observes increased glycogen breakdown. When a phosphodiesterase inhibitor is added, the stimulatory effect is prolonged. Which of the following best explains why phosphodiesterase inhibition prolongs the cellular response?

A somatic cell acquires two mutations: one converts a proto-oncogene into a constitutively active oncogene, and a second inactivates a tumor suppressor gene. Which of the following best predicts the cellular outcome?

Which of the following best describes a key difference between mitosis and meiosis II?

A graph tracks the relative amount of DNA per cell over time. DNA content doubles during one phase, then is halved twice in succession. Which sequence of phases correctly accounts for the doubling and the two halvings?

In pea plants, tall (T) is dominant over short (t) and round seed (R) is dominant over wrinkled (r). A plant with genotype TtRr is crossed with a plant of genotype ttRr. What fraction of offspring is expected to be tall with wrinkled seeds?

In cats, coat color shows incomplete dominance: BB = black, WW = white, BW = gray. Two gray cats are crossed, and offspring are: 25 black, 42 gray, 23 white. A chi-square test yields χ² = 1.84. The critical value at p = 0.05 with 2 degrees of freedom is 5.99. Which conclusion is most appropriate?

A color-blind male (X-linked recessive, genotype X^bY) has children with a female who is a carrier for color blindness (genotype X^BX^b). What is the probability that their daughter will be color-blind?

In a Meselson-Stahl-style experiment, bacteria grown in ¹⁵N medium are transferred to ¹⁴N medium. After one round of replication, all DNA appears at an intermediate density. After two rounds, half is at intermediate density and half is at light density. Which model of replication is supported?

A scientist discovers a drug that specifically blocks the binding of aminoacyl-tRNA to the ribosomal A site. Which cellular process is directly inhibited by this drug?

The table below shows β-galactosidase activity in E. coli under four conditions:

Which of the following best explains the low activity observed in Condition 3?

A point mutation in a gene changes a single nucleotide, producing a synonymous (silent) codon that encodes the same amino acid as the original. In a large, randomly mating population, which of the following best predicts the evolutionary fate of this mutation?

A forensic scientist uses PCR to amplify a specific DNA region from a crime scene sample, then runs the products on a gel alongside a DNA size ladder. Which of the following correctly describes the distinct contribution of PCR and gel electrophoresis to this analysis?

In a population of mice in a snowy environment, mice with intermediate coat colors survive at lower rates than mice with either very white or very dark coats, which are both more difficult for predators to detect in different microhabitats. This pattern is best described as which type of natural selection?

In a population of 1,000 butterflies, 360 are homozygous dominant (AA), 480 are heterozygous (Aa), and 160 are homozygous recessive (aa). Using Hardy-Weinberg calculations, what are the allele frequencies p (dominant allele) and q (recessive allele)?

A fish population in a large lake is divided into two isolated ponds by a prolonged drought. After 10,000 years, the water reconnects, but the two populations can no longer produce viable offspring with each other. The populations remain morphologically similar. Which type of speciation occurred, and which broad category of reproductive isolation is described?

A cladogram places species X, Y, and Z in a clade united by the shared derived character of a hinged jaw. Species W is the outgroup and lacks a hinged jaw. A student concludes that X and Y are more closely related to each other than either is to Z, citing only their physical similarity. Which of the following best evaluates this conclusion?

Following a volcanic eruption, 15 beetles colonize a new island. The founding group carries an unusually high frequency of a rare allele with no known fitness advantage. Over subsequent generations, this allele becomes fixed in the island population. Which evolutionary mechanism best explains this outcome?

A researcher tracks a deer population over 20 years. The population grows exponentially for the first 10 years, then growth slows and the population stabilizes. Which of the following best explains the shift from exponential to logistic growth?