Question

Which of the following are characteristics of

biological membranes?

(i) Membranes are fluid structures.

(ii) The sugar residues of membrane are always located on the external surface of plasma membranes.

(iii) The outer and inner surfaces of all known biological membranes have different components and different enzymatic activities, i.e., membranes are asymmetric.

(iv) Membrane fluidity is controlled by fatty acid composition and protein distribution.

(v) Membrane proteins and phospholipids can readily rotate within the membrane, from the inside to the outside surface.

(i), (ii), (iii), (iv)

(i), (ii), (iii), (iv), (v)

(i), (ii), (iv)

(i), (ii), (v)

(i), (ii), (iii)

Answer 1

Last option which have given statements i,ii,iii is the correct one becausethese given three statements are true for a biological membrane.

i) Membranes are of fluid mosaic structure as it is made up of lipid bilayer which functions both as solvent for Integral proteins and as a permeabiality barrier.

ii)the sugar residues are always located on external surface.

iii) membranes are asymmetric in their distribution on the two sides of the bilayer as some lipids typically are found primarily inouter surface of the bilayer and some in inner face which makes the two faces having different components and enzymatic activities.

iv) membrane fluidity is very much controlled by fatty acid composition because it directly depends upon the type of fatty acid chain present in bilayer but it is not affected at all by the protein distribution so this option is incorrect.

v) individual phospholipids can only move within. The membrane but not always so this option is also not correct.