AP Biology MCQ 2 — Questions and Answers
Question 1: Which organelle is responsible for producing ATP through cellular respiration?
- Nucleus
- Mitochondria (Correct answer)
- Ribosome
- Golgi apparatus
Correct answer: Mitochondria
Mitochondria are the powerhouse of the cell, producing ATP through oxidative phosphorylation.
Mitochondria perform cellular respiration, converting glucose and oxygen into ATP (adenosine triphosphate) through glycolysis, the Krebs cycle, and the electron transport chain.
Question 2: DNA replication is described as semi-conservative because:
- Only half the DNA is copied
- Each new molecule contains one original and one new strand (Correct answer)
- The process is 50% accurate
- It occurs in half the cell cycle
Correct answer: Each new molecule contains one original and one new strand
Semi-conservative means each daughter DNA molecule has one parent strand and one newly synthesized strand.
Watson and Crick proposed that DNA replication is semi-conservative: the double helix unwinds, each strand serves as a template, and each new double helix contains one original (parent) and one newly synthesized (daughter) strand.
Question 3: Which type of selection favors individuals at both extremes of a trait?
- Stabilizing selection
- Directional selection
- Disruptive selection (Correct answer)
- Artificial selection
Correct answer: Disruptive selection
Disruptive selection favors extreme phenotypes over intermediate ones.
Disruptive (diversifying) selection favors individuals at both extremes of the phenotypic range while selecting against intermediate phenotypes. This can lead to speciation if the two groups become reproductively isolated.
Question 4: The Calvin cycle occurs in which part of the chloroplast?
- Thylakoid membrane
- Stroma (Correct answer)
- Inner membrane
- Outer membrane
Correct answer: Stroma
The Calvin cycle (light-independent reactions) takes place in the stroma of the chloroplast.
The Calvin cycle occurs in the stroma, the fluid-filled space surrounding the thylakoids. It uses ATP and NADPH from the light reactions to fix carbon dioxide into G3P, which is used to build glucose.
Question 5: Which molecule carries amino acids to the ribosome during translation?
- mRNA
- tRNA (Correct answer)
- rRNA
- DNA
Correct answer: tRNA
Transfer RNA (tRNA) carries specific amino acids to the ribosome, matching codons on mRNA.
tRNA molecules have an anticodon that pairs with the corresponding mRNA codon and carry the appropriate amino acid. Each tRNA is charged with a specific amino acid by aminoacyl-tRNA synthetase enzymes.
Question 6: Hardy-Weinberg equilibrium requires all of the following EXCEPT:
- Large population
- No mutation
- Random mating
- Natural selection (Correct answer)
Correct answer: Natural selection
Natural selection disrupts Hardy-Weinberg equilibrium by favoring certain alleles.
Hardy-Weinberg equilibrium requires: large population (no genetic drift), no mutation, random mating, no gene flow, and no natural selection. If any condition is violated, allele frequencies will change (evolution occurs).
AP Biology MCQ 2
Which organelle is responsible for producing ATP through cellular respiration?