DDT was once considered a ʺsilver bulletʺ that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

#Question id: 2203

#Unit 2. Cellular Organization

Parietal cells acidify the stomach contents while maintaining a neutral cytosolic pH by: 

a. exporting “excess” cytosolic OH– as HCO3–.
b. exchanging HCO3– for Cl–.
c. preserving electroneutrality by accompanying the movement of each Cl– ion into the stomach lumen by a K+.
d. the excess K+ ions pumped inward by the H+/K+ ATPase are returned to the stomach lumen, thus maintaining the normal intracellular K+ concentration.
Which of the following combination is correct?

#Question id: 2204

#Unit 2. Cellular Organization

A mutant channel protein is expressed in an oocyte. Compared to patch clamping experiments in oocytes expressing the normal channel, the length of downward deviations is diminished by half. This indicates:

#Question id: 2205

#Unit 2. Cellular Organization

Amino acid entry into cells can occur via uniporters or symporters. If the rate of leucine entry into the cell increases when the pH decreases, this suggests:

#Question id: 2206

#Unit 2. Cellular Organization

The glucose uniporter GLUT1 has a Km of 1.5 mM for D-glucose and 30 mM for D-galactose.  At a concentration of 5 mM for each, what is the rate of glucose transport relative to galactose transport?  The Vmax may be assumed to be the same for both.

#Question id: 2207

#Unit 2. Cellular Organization

Why was it unexpected that transporter proteins are required for transmembrane fatty acid transport?

#Question id: 2208

#Unit 2. Cellular Organization

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?