DAT Question of the Day

Correct Answer: A. moves 3 Na⁺ out and 2 K⁺ in the cell

Maintenance of the cell membrane potential is conducted by keeping a low concentration of Na ions and high concentration of K ions inside the cell. The pump uses ATP energy to expel three Na ions out of the cell. Also, the pump enables entrance of two K ions into cell. However, the resting potential of the membrane IS NOT as a result of pumping out 3 positive ions and only pumping in 2 positive ions. The resting potential is achieved due to the impermeability of the membrane to the ions.

Subscribe below to get the DAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: C. depolarization of the beta cell membrane leads to an increased level of intracellular Ca2+

To begin, glucose is transported into the beta cell. As a result of glucose metabolism, ATP molecules are generated. An increased level of ATP inhibits the KATP channel, preventing entrance of K⁺ ions into the cell. The consequence of this action is depolarization of the cell membrane and subsequent activation of the VDCC. Ca²⁺ ions enter into the cell stimulating exocytosis of insulin. This is a great example of an application question in the biology section of the DAT.

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

Correct Answer: D. The plant went through photosynthesis but at a lower rate than normal.

The plant cell in shade has some access to sunlight, but it is limited since the cell is in the shade. Since methylene blue is in the test tube, the color in the test tube should become darker, more and more blue as the plant produces oxygen and goes through photosynthesis. Plant cell 1 is the control group and as you can see the percent transmittance of light decreases over the 3 days because of the high rate of photosynthesis and production of oxygen. The plant cell in the closet had no access to sunlight and was able to go through some photosynthesis on the first day but virtually none the other 2 days, which is why the percent transmittance remained high, signaling low levels of oxygen produced and low levels of blue pigment present.

Subscribe below to get the DAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: A. mutation in codon 288

The genetic code is degenerate. It means that a particular amino acid is determined by multiple codons. These codons usually have a different third “letter”. This is known as genetic “wobble”. For example, the amino acid serine is determined by the following codons: TCT, TCC, TCA, TCG. Based on this, a mutation in codon 288 does not change the polypeptide structure because GAA and GAG code for the same amino acid. This mutation will not affect cancer development.

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

Correct Answer: A. increased production of HCl by parietal cells acts stimulatory on gastrin secretion

Gastrin stimulates parietal cells to release HCl. If A were true, then there would be a positive feedback loop where gastrin is stimulating more HCl production, and HCl is stimulating more gastrin production, causing us to burn a hole through our stomach! Increased production of HCl by parietal cells leads to somatostatin secretion, which inhibits the secretion of gastrin. Lastly, an elevated gastric pH (i.e. low amount of acid) would stimulate the G cells to release more gastrin in an attempt to stimulate the parietal cells to release more HCl to bring the acidity back to normal.

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

Correct Answer: C. (1) Sodium (2) Potassium (3) Calcium

Neurons are at rest with a negative membrane potential relative to the outside of the cell. During an action potential, positively charged sodium ions rush into the cell making the membrane potential less negative (depolarization). Soon after, potassium (another positively charged ion) exits the cell and restores polarization. The presynaptic terminal reacts to the action potential by opening calcium channels. This calcium is required for the cellular machinery responsible for neurotransmitter release into the synapse.

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

Correct Answer: E. A and C

During the evolution of living systems, there were two ways the velocity of nerve impulse propagation could be increased. The first way was increasing nerve diameter, while the second way was the formation of the myelin sheath. The latter mechanism is less energetically expensive than the former.

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