Following statements are regarding to anterior-posterior polarity in planaria.

A. The anterior expression of Notum functions to antagonize the posteriorly produced Wnt, leading to head specification.

B. Regulation of the balance between Wnt and Notum signals may underlie not only head-tail specification but also regulation of organ size.

C. In addition, there appears to be an anterior-to-posterior gradient of Erk signaling that functions as a positive inducer of tail specification.

D. Wnt signaling achieves its repression of head regeneration by inhibiting Erk. Therefore, only in those more anterior regions lacking Wnt (due to Notum’s repression of Wnt) can Erk induce head regeneration.

Which of the following statements are incorrect?

#Question id: 2201

#Unit 2. Cellular Organization

Much of what we know about the nicotinic acetylcholine receptor has come from studies of:

#Question id: 2202

#Unit 2. Cellular Organization

The distribution of K⁺ across an artificial membrane was measured, and the concentrations were found to be equal on both sides. Which of the following statements is true about the distribution of K⁺?

#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.