MCAT Question of the Day

Correct Answer: C. cellular respiration

In the cell, metabolism is defined as the chemical reactions that occur within the cell to sustain life. Metabolism can further be divided into anabolism (the synthesis of new compounds) and catabolism (breaking down of substances). Answer options A, B, D, and E are all anabolic processes, that require the use of energy to make new compounds. In cellular respiration, glucose is broken down to produce ATP, therefore this is a catabolic process.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: D. The amount of salt reabsorbed in the kidneys will increase.

Aldosterone is a hormone released from the adrenal gland. Its presence in the blood helps the kidney’s retain more sodium chloride (NaCl) in the nephrons, thereby desalinating the urine. Glucose regulation is controlled by the pancreas’ release of insulin. Calcium ion levels are controlled by calcitonin and parathyroid hormone. The amount of water retained by the kidneys is controlled by the release of the antidiuretic hormone (ADH) or vasopressin. Aldosterone helps to retain water too, so the amount of water excreted by the body will decrease. Therefore, the correct answer is [D].

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: A. Blood is pumped from the ventricles to the arteries.

Systole is the state of contraction of the heart muscles. The heart contracts to pump blood out of the ventricles and into the arteries to move the blood to the body. During diastole or when the heart is resting, blood collects in the chambers of the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. During systole, the blood is being pumped away from the heart, thereby the use of arteries is essential. The only answer option that aligns with the correct function of the heart during systole is [A].

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. An inhibitor binds directly to the active site and prevents the reactant from binding

The correct answer is B. Metal cofactors and ATP are often used to help boost enzyme activity, and are not competitive inhibitors. Non-competitive inhibition(D) occurs when an inhibitor is able to prevent the enzyme from binding with the reactant by binding to the enzyme at a site away from the active site, and change the enzyme’s conformation so it cannot bind to the reactant. Competitive inhibition occurs when the inhibitor competes directly with the reactant at the active site, and this substrate takes the place of the reactant and prevents the reaction from occurring.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. Reflex Arc

A reflex arc is a nervous system process whereby the stimulus causes a motor movement that is coordinated by the spinal cord and not the brain. Sensory neurons are able to capture the environmental stimuli and send the afferent signal to the spinal cord, which is able to send an efferent (motor) signal directly to the effector, a muscle, which then moves. Plasticity refers to the brain’s ability to repair itself following damage. Metabolism is the general term defining the cell’s use and production of energy. Redirection is not an accurate term and is not used in biology. Depolarization is the process of changing the cell membrane’s to become more positive, commonly observed when in the nervous system with the propagation of an action potential. Therefore the correct answer is [B].

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: D. Klinefelter Syndrome

Klinefelter syndrome is a result of an extra X chromosome in men. The syndrome is normally not diagnosed until after puberty, and its outward symptoms are mild. Generally, men are diagnosed when they seek treatment for symptoms of other diseases or infertility.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: C. Vacuole

The correct answer is C. Cells within the Kingdom Plantae have chlorophyll containing cells called CHLOROPLASTS, a rigid cell WALL outside of the plasma membrane, and vacuoles that serve to store carbohydrates. Plant cells do not contain lysosomes, as other eukaryotic cells, instead they have peroxisomes for digestion of foreign material.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: D. Blending of the pronucleus from the ovum and sperm into one.

The blending or fusing of the pronuclei from the oocyte and the sperm cell does not occur, in that the two do not become one. What does occur is that the protective membranes on both dissolve, allowing for the genetic material to co-mingle. A mitotic spindle is formed and attaches itself to the chromosomes from each pronucleus before the chromosomes are fully dispersed throughout the cytoplasm of the oocyte. Mitosis then takes place creating daughter cells that are genetically identical. You may remember that all of a female’s eggs are arrested at meiosis II. The eggs remain in this stage until sperm fertilizes them.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. 25%

The resulting progeny will have 4 violets with blue-pointed petals out of a total of 16 possible combinations. If we generate a Punnet Square, we can lay out the alleles in the genetic cross. As we can see, there are 16 combinations possible, 12 of which result in red-pointed petals and 4 of which result in blue-pointed petals.

There are no combinations featuring rounded petals, because the first flower did not contain any recessive alleles for X, and therefore all the resulting progeny in the cross have pointed petals.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. Polyphyletic and heterotrophic.

Fungi are a classified as a group based upon common biological traits acquired through convergent evolution, without a common ancestor, and are therefore considered polyphyletic. Unlike plants, fungi cannot make their own food supply. Instead, they obtain nutrition by parasitism, saprobism or symbiosis.

Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.