Free MCAT-TEST sample questions

Correct answer: Aspartic Acid, then Valine, then Lysine

At pH 6.0, aspartic acid (pI=2.8) is well above its pI and will have a net negative charge. Valine (pI=6.0) will have a net charge of zero. Lysine (pI=9.7) is well below its pI and will have a net positive charge. A cation-exchange column contains a negatively charged stationary phase. Therefore, the negatively charged aspartic acid will be repelled and elute first. The neutral valine will have minimal interaction and elute next. The positively charged lysine will bind tightly to the column and elute last, likely requiring a change in buffer pH or salt concentration to be released.

Correct answer: An increased end-systolic pressure and a decreased stroke volume.

Chronic hypertension increases the afterload, which is the pressure the left ventricle must overcome to eject blood into the aorta. This requires the ventricle to generate a higher pressure during systole, leading to an increased end-systolic pressure. The increased afterload makes it harder for the ventricle to eject blood, resulting in a larger end-systolic volume and consequently a smaller stroke volume (the width of the PV loop). The loop shifts to the right and becomes taller and narrower.

Correct answer: True

This statement is true. Negative reinforcement strengthens a behavior by removing an unpleasant stimulus (e.g., taking an aspirin removes a headache, making you more likely to take aspirin for future headaches). Punishment (specifically, positive punishment) weakens a behavior by adding an unpleasant stimulus (e.g., getting a speeding ticket makes you less likely to speed). The key distinction is that reinforcement (both positive and negative) always increases a behavior, while punishment always decreases a behavior.

Correct answer: Velocity increases and pressure decreases.

The continuity equation states that for an incompressible fluid, the product of the cross-sectional area (A) and velocity (v) is constant. As the artery constricts, A decreases, so the velocity (v) must increase. Bernoulli's principle states that for a horizontal pipe, an increase in fluid speed is associated with a decrease in pressure. Therefore, as the blood velocity increases through the stenosis, the lateral pressure it exerts on the artery walls decreases.

Correct answer: Hypokalemia, hypernatremia, and metabolic alkalosis.

Aldosterone's primary functions in the distal convoluted tubule and collecting duct are to increase the reabsorption of sodium (Na+) and water, and to increase the secretion of potassium (K+) and hydrogen ions (H+). Excessive aldosterone would lead to increased Na+ reabsorption (hypernatremia), increased K+ secretion (hypokalemia), and increased H+ secretion (metabolic alkalosis).

Correct answer: Social exclusion

Social exclusion refers to the process by which individuals or groups are pushed to the fringe of society and prevented from participating fully due to factors like poverty, lack of skills, or discrimination. In this context of gentrification, the original residents are being socially and culturally excluded from their own changing neighborhood, even if they haven't been physically displaced yet. Anomie is normlessness, cultural lag is the gap between material and non-material culture, and residential segregation is the physical separation of groups, which is related but less specific than the feeling of exclusion described.

Correct answer: It shifts the curve to the right, decreasing oxygen affinity.

2,3-BPG is a negative allosteric regulator of hemoglobin. It binds preferentially to the deoxygenated (T-state) form of hemoglobin, stabilizing this low-affinity conformation. By stabilizing the T-state, it makes it more difficult for oxygen to bind, thereby decreasing hemoglobin's overall affinity for oxygen. This results in a rightward shift of the oxygen-hemoglobin dissociation curve, which facilitates oxygen release to the tissues.

Correct answer: Two peptides: Ala-Gly-Cys-Met and Lys

Cyanogen bromide (CNBr) specifically cleaves the peptide bond on the carboxyl (C-terminal) side of methionine (Met) residues. In the sequence Ala-Gly-Cys-Met-Lys, the cleavage will occur after the Met residue. This will break the bond between Met and Lys, resulting in two fragments: the tetrapeptide Ala-Gly-Cys-Met and the single amino acid Lys.

Correct answer: Formal Operational Stage

The formal operational stage, which typically begins around age 12, is characterized by the development of abstract reasoning. Individuals in this stage can think about hypothetical scenarios, deduce consequences (hypothetical-deductive reasoning), and understand abstract principles like justice and algebra. The concrete operational stage is limited to logical thought about concrete events, while the earlier stages are pre-logical.

Correct answer: The genes will be expressed constitutively in both conditions.

The operator is the binding site for the repressor protein. Normally, the repressor binds to the operator in the absence of lactose, blocking transcription. If a mutation prevents the repressor from binding, this negative control is lost. In the absence of glucose, cAMP levels are high, and CAP is active, promoting transcription. Since the repressor cannot bind to the mutated operator, RNA polymerase will be free to transcribe the genes regardless of whether lactose is present or not. This results in constitutive (continuous) expression.