OAT General Biology 3 — Questions and Answers
Question 1: A cell with a water potential of -0.4 MPa is placed in a solution with a water potential of -0.2 MPa. Water will:
- Move into the cell
- Move out of the cell (Correct answer)
- Not move
- Move in both directions equally
Correct answer: Move out of the cell
Water moves by osmosis from higher (less negative) to lower (more negative) water potential, so water exits the cell toward the -0.2 MPa solution.
Question 2: Which stage of cellular respiration produces the most ATP per glucose molecule?
- Glycolysis
- Pyruvate oxidation
- Krebs cycle
- Oxidative phosphorylation (Correct answer)
Correct answer: Oxidative phosphorylation
Oxidative phosphorylation (electron transport chain + chemiosmosis) generates approximately 32-34 ATP per glucose, far more than the other stages.
Question 3: What is the function of the sinoatrial (SA) node in the heart?
- Prevents backflow of blood
- Initiates the electrical impulse for each heartbeat (Correct answer)
- Controls blood pressure
- Regulates oxygen levels
Correct answer: Initiates the electrical impulse for each heartbeat
The SA node is the heart's natural pacemaker, spontaneously generating electrical impulses that trigger each cardiac contraction.
Question 4: Which of the following is a characteristic feature of prokaryotic cells?
- Membrane-bound nucleus
- Mitochondria
- 70S ribosomes (Correct answer)
- Endoplasmic reticulum
Correct answer: 70S ribosomes
Prokaryotes have 70S ribosomes (composed of 50S and 30S subunits), while eukaryotes have 80S ribosomes in the cytoplasm.
Question 5: Hardy-Weinberg equilibrium requires which of the following conditions?
- Small population size
- Natural selection acting on the trait
- Random mating among individuals (Correct answer)
- High mutation rates
Correct answer: Random mating among individuals
One of the five Hardy-Weinberg assumptions is random mating; violations of this or other assumptions cause allele frequencies to change over time.
Question 6: Which hormone is primarily responsible for stimulating the fight-or-flight response?
- Insulin
- Cortisol
- Epinephrine (Correct answer)
- Thyroxine
Correct answer: Epinephrine
Epinephrine (adrenaline), released by the adrenal medulla, rapidly triggers the fight-or-flight response by increasing heart rate, dilating airways, and mobilizing energy.
Question 7: What type of bond holds the two strands of a DNA double helix together?
- Ionic bonds
- Covalent bonds
- Hydrogen bonds (Correct answer)
- Peptide bonds
Correct answer: Hydrogen bonds
Complementary base pairs (A-T and G-C) between the two DNA strands are held together by hydrogen bonds, which are weak but collectively stable.
OAT General Biology 3
A cell with a water potential of -0.4 MPa is placed in a solution with a water potential of -0.2 MPa.
Water will: