GACE Biology 4 — Questions and Answers
Question 1: Which phase of the cell cycle involves DNA replication?
- G1 phase
- S phase (Correct answer)
- G2 phase
- M phase
Correct answer: S phase
DNA replication occurs during the synthesis (S) phase of interphase, duplicating each chromosome before cell division.
Question 2: According to the fluid mosaic model, what is the primary component that gives the cell membrane its fluidity?
- Peripheral proteins
- Carbohydrate chains
- Phospholipid bilayer (Correct answer)
- Cholesterol only
Correct answer: Phospholipid bilayer
The phospholipid bilayer forms the flexible, fluid matrix of the cell membrane, with proteins and other molecules embedded or attached within it.
Question 3: A teacher is explaining feedback inhibition in metabolic pathways. Which scenario best illustrates this concept?
- Glucose stimulates insulin release, which promotes glucose uptake
- The end product of a biosynthetic pathway inhibits the first enzyme of that pathway (Correct answer)
- A substrate increases the production of the enzyme that metabolizes it
- A hormone activates a second messenger cascade
Correct answer: The end product of a biosynthetic pathway inhibits the first enzyme of that pathway
Feedback inhibition (negative feedback) occurs when the final product of a pathway allosterically inhibits an early enzyme, preventing overproduction.
Question 4: Which kingdom includes organisms that are prokaryotic, lack a nucleus, and can survive in extreme environments such as hot springs and salt flats?
- Protista
- Bacteria
- Archaea (Correct answer)
- Fungi
Correct answer: Archaea
Archaea are prokaryotes that uniquely inhabit extreme environments and differ from Bacteria in membrane lipid composition and other molecular features.
Question 5: Which Hardy-Weinberg condition is violated when a small isolated population of deer loses rare alleles simply due to random chance?
- No mutation
- No gene flow
- No genetic drift (large population size) (Correct answer)
- Random mating
Correct answer: No genetic drift (large population size)
Genetic drift — random allele frequency changes — is most pronounced in small populations, violating the Hardy-Weinberg assumption of infinitely large population size.
Question 6: During aerobic cellular respiration, the Krebs cycle occurs in the:
- Cytoplasm
- Mitochondrial matrix (Correct answer)
- Inner mitochondrial membrane
- Nucleus
Correct answer: Mitochondrial matrix
The Krebs (citric acid) cycle takes place in the mitochondrial matrix, where acetyl-CoA is oxidized and electron carriers NADH and FADH₂ are produced.
Question 7: Which type of RNA is catalytic and can function as an enzyme to catalyze biochemical reactions?
- mRNA
- tRNA
- rRNA
- Ribozyme (Correct answer)
Correct answer: Ribozyme
Ribozymes are RNA molecules with catalytic activity, capable of cleaving RNA substrates or catalyzing peptide bond formation at the ribosome.
GACE Biology 4
Which phase of the cell cycle involves DNA replication?