Question

b) Consider the following scenario: You start an experiment with equal concentrations of sodium chloride in a small tank. You are interested in studying the nature of a transmembrane protein embedded in a lipid bilayer. You insert the membrane, with embedded protein, into the tank, creating two sides, with initially the same concentrations of a solute on both sides (side A and side B). You leave the experiment for several hours and when you return you find that the solutes are at a higher concentration on side B than side A. Sketch a drawing of this experiment and then list your hypothesis about the nature of the transmembrane protein, using the classifications discussed in Chapter 6, especially figure 6.27.

Answer 1

The diagram or the Sketch of the experiment is enclosed here-

Hypothesis of the experiment:-

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There must be a type of carrier protein or integral transmembrane protein in the membrane that is responsible for the transportation of Na+ ion across the membrane from side A to B against the electrochemical gradient.

Here, the transmembrane proteins are the carrier protein that is responsible for the active transport of molecules from one side to other across the membrane. Here, the transmembrane protein must be a Na+/ K+- ATPase pump which is actively transporting Na+ ions across the membrane utilising the energy derived from hydrolysis of ATP. For every ATP molecule consumed this Na+ / K+ pump will transfer 3 Na+ ion on side B and 2 K+ ion on side A of the experiment. This pump is made  three subunits α, β, and FXYD(gamma). The α-subunit is the largest subunit and it contains the binding sites for Na⁺, K⁺, and ATP. The β-subunit is a single spanning membrane protein with a transmembrane α-helix and a glycosylated extracellular domain. and the γ-subunit, is an accessory regulatory protein comprising a transmembrane α-helix and an extracellular domain.