Question

Consider the transport of a potassium ion from the blood (where its concentration is about 4.5 mM) into a Red Blood Cell that contains 140 mM K⁺ at a temperature of 298 K. The transmembrane potential is about 58 mV, inside negative relative to outside.

a) What type of transport must be used to move potassium ions across the Red Blood Cell outer membrane? (Simple diffusion, Facilitated diffusion, or active transport)

b)In terms of the functioning of the beta-adrenergic pathway, give the rationale for the fact that the alpha subunit of the G-protein is secluded in a trimeric protein and bound to a GPCR when no epinephrine is available.

c) In terms of the functioning of the beta-adrenergic pathway, give the rationale for the fact that adenalyl cyclase converts ATP to cAMP.

Answer 1

a) Active transport must be used to move K+ ion across the red blood cell outer membrane because transport K+ is a against the membrane potential.

b) In beta adrenergic Pathway , Alpha subunit of the G-protein is secluded in the trimeric protein and bound to GPCR when no epinephine is available is due to the desensitization of receptor by prolong and repeated exposure of agonist.

c)Activated adenyl cyclase convert the ATP to cAMP for the activation of cAMP-dependent Protein Kinase. Inactive protein kinase contain two inhibitory regulatory subunits(R) and two catalytic subunits(C). Regulatory subunits binds to the substrate binding sites of catalytic subunit. cAMP dissociates the regulatory subunits from catalytic subunits and activate  protein kinase. Active protein Kinase phosphorylate the no. of enzymes in metabolic pathway.