Question

Life has been found on a newly discovered planet not too far from our solar system! The planet is named Nairb. A mission was sent to Nairb to learn more about these new life forms and the following data was obtained. The life forms on Nairb have a similar appearance to those of earth. These new life forms are also composed of many very similar molecular building blocks to life forms on earth, for example: amino acids and lipids are the same. However, there is one huge difference: on Nairb cells have the nonpolar solvent hexane substituted in the place of water. How would Nairb would differ from that of earth.

a) What would the structure of membranes would be like in the cells of life forms on Nairb?

b) What would the structure of transmembrane proteins be like in cells on Nairb?

c) What would the structure, folding, and primary sequence of a ‘soluble’ (free in solution) protein be like in cells on Nairb?

Answer 1

a)  The structure of membranes in the cells of life forms on Nairb will vary drastically from that of the biomembranes on earth. As, we know that biomembranes consist of the lipid bilayer which is arranged in such a way that hydrophobic tails are intact inside the bilayer and hydrophobic heads are towrds outside where water is present. But, when the solvent outside is non polar this lipid will dissolve in the hexane and bilayer will be broken down leading to the more fluidity of the memrane. Even, the permeability of the memrane will be enhanced leading to no control over the permeability of any substances.

b) In cells on Nairb, the structure of transmembrane proteins will be denatured and they will be free. These transmembrane proteins are amphipathic like lipids, their  hydrophobic regions pass through the membrane and interact with the hydrophobic tails of the lipid molecules in the interior of the bilayer, where they are sequestered away from water but their hydrophobic regions are exposed to water on either side of the membrane. But, when hexane is present the lipid bilayer would be broken down and so this transmembrane proteins would not be intact in the lipid bilayer with its hydrophobic regions protected they will also undergo structural denaturation and will be free floating with no Alpha helix and beta Barrel transmembrane structure.

C)The structure folding, and primary sequence of a ‘soluble protein in cells on Nairb would not be like that on the earth where they undergo several modifications primary secondary and tertiary foldings to form distinct protein and hide the hydrophobic end into the interior of the structure.. The proteins will be highly stable and would not dissolve at all in hexane. Generally in water soluble proteins the hydrophobic groups is kept away from water, while polar groups is exposed.Thus the interior of the protein is almost entirely hydrophobic while the exterior is more polar. This, will be reversed and there will be no such structural organisation as the solvent outside is non polar, and no fear of instability will be there.