MCAT Psy Domain 3: Biology Welcome to your MCAT Psy Domain 3: Biology 1. MCAT Psy: Biology Which of the following statements accurately describes the role of microRNA 'miRNA' in gene expression? miRNA destroys mRNA molecules, preventing translation. miRNA adds a methyl group to DNA, enhancing gene expression. miRNA facilitates the ribosome's ability to translate mRNA. miRNA enhances gene expression by stabilizing mRNA molecules. None 2. MCAT Psy: Biology During embryonic development, which of the following processes correctly describes the formation of the neural tube? Gastrulation leads to the formation of the ectoderm, which then folds to form the neural tube. Neurulation involves the mesoderm folding to form the neural tube. The neural tube forms from the endoderm folding inward during neurulation. The neural tube is formed by the fusion of lateral ectodermal folds. None 3. MCAT Psy: Biology What is the primary function of the sodium-potassium pump (Na+/K+ ATPase) in neuronal cells? To depolarize the neuronal membrane by increasing sodium ion concentration inside the cell. To hyperpolarize the neuronal membrane by increasing potassium ion concentration inside the cell. To maintain the resting membrane potential by pumping sodium ions out and potassium ions in. To facilitate the diffusion of sodium and potassium ions across the membrane without ATP consumption. None 4. MCAT Psy: Biology In the context of enzyme kinetics, how does a noncompetitive inhibitor alter an enzyme's activity? It binds to the active site, preventing substrate binding. It increases the maximum velocity (Vmax) of the enzyme. It decreases the affinity of the enzyme for its substrate, lowering Km. It binds to an allosteric site, decreasing Vmax without affecting Km. None 5. MCAT Psy: Biology Which of the following cell types is primarily responsible for the synthesis and secretion of antibodies? T lymphocytes Plasma cells Mast cells Macrophages None 6. MCAT Psy: Biology During the citric acid cycle (Krebs cycle), which compound donates an acetyl group to oxaloacetate to form citrate? NADH Acetyl-CoA ATP Pyruvate None 7. MCAT Psy: Biology What is the primary role of leptin in the human body? To stimulate hunger and reduce metabolic rate. To promote glucose uptake into cells, reducing blood sugar levels. To signal satiety and regulate energy balance by inhibiting hunger. To enhance the absorption of fatty acids from the digestive tract. None 8. MCAT Psy: Biology Which of the following mechanisms best describes the action of steroid hormones on their target cells? Binding to cell surface receptors and activating secondary messenger systems. Entering the cell and directly activating specific genes in the DNA. Inhibiting gene transcription by binding to DNA promoters. Altering membrane permeability by binding to ion channels. None 9. MCAT Psy: Biology The passage of substances across the blood-brain barrier 'BBB' is highly selective. Which of the following substances is most likely to cross the BBB through passive diffusion? Glucose Sodium ions Oxygen Large proteins None 10. MCAT Psy: Biology What is the significance of the "wobble" position in tRNA anticodons during translation? It allows for the precise matching of tRNA anticodons with mRNA codons, enhancing translation fidelity. It prevents the initiation of translation by binding to the small ribosomal subunit. It facilitates the binding of tRNA to the ribosome, increasing the efficiency of protein synthesis. It permits flexibility in base pairing at the third position of the mRNA codon, allowing a single tRNA to recognize multiple codons. None 1 out of 10 Time is Up! Time's up
