In heart muscle, activation series of the muscarinic acetylcholine receptor its effector K+ channel via the Gβγ subunit of a Gi protein.

a. Binding of acetylcholine triggers activation of the Gαi subunit and its dissociation from the Gβγ subunit in the usual way. 

b. The released Gβγ subunit (rather than Gαi∙GTP) binds to and opens the associated effector protein, a K+ channel. 

b. The increase in K+ permeability hyperpolarizes the membrane, which reduces the frequency of heart muscle contraction. 

d. Activation is terminated when the GTP bound to Gαi is hydrolyzed (by a GAP enzyme that is an intrinsic part of the Gαi subunit) to GDP and Gαi∙GDP recombines with Gβγ.

#Question id: 10495

#Unit 6. System Physiology – Plant

Guard cells have different mechanisms mediating responses to blue light. The npq1 mutant has a lesion in the enzyme that covert violaxanthin to zeaxanthin. What will causes if the npq1 mutant?

#Question id: 10494

#Unit 6. System Physiology – Plant

Sucrose is an osmotically active solute in guard cells, One implication of these osmoregulatory features is that stomatal opening & closing is associated with which of the following given statements?

#Question id: 10493

#Unit 6. System Physiology – Plant

Which wavelength modulates guard cell osmoregulation by means of its activation of proton pumping, solute uptake, and stimulation of the synthesis of organic solutes;

#Question id: 10491

#Unit 6. System Physiology – Plant

Acidification of the lumen stimulates zeaxanthin formation, and alkalinization favors violaxanthin formation. Lumen pH depends on photosynthetic photon flux density, most effective at

#Question id: 10490

#Unit 6. System Physiology – Plant

Which of the following is a correct Match of the stomatal opening and closing mechanism;

#Question id: 10489

#Unit 6. System Physiology – Plant

Malate anions, by contrast, are synthesized in the guard cell cytosol, in a metabolic pathway that uses carbon skeletons generated by