Question

If polar amino acids are found in a membrane spanning α-helical region, they are most likely _____.

hydrogen-bonded with hydroxyl groups of the membrane fatty acids

none of the above

modified with nonpolar groups by prenylation, methylation and/or acylation

hydrogen-bonded to other polar amino acids to prevent interaction with the membrane lipids

mutations

Q2: Which of the following will cause the opening or closing of a gated ion channel?

voltage change

ligand binding

phosphorylation

pH change

All of the above

Answer 1

Q1 hydrogen-bonded to other polar amino acids to prevent interaction with the membrane lipids

(Membrane proteins can be either alpha - helices or beta - strands. Membrane - spanning alpha - helices are the most common structural motif. most of the amino acids in the membrane protein are non-polar however few are charged. The polar amino-acids bond to the other polar amino acids so as to prevent their interaction with the lipids of the membrane)

Q2 all of the above

(Most ion channels are gated which means they either open or close spontaneously or in response to a specific stimulus, for example, the binding of a small molecule to the channel protein (ligand-gated ion channels) or a change in voltage across the membrane (voltage-gated ion channels). Ion channels are also controlled by phosphorylation/dephosphorylation)