Question

Identify and explain two ways in which plasma membranes can remain fluid when the temperature drops.

a. Decreasing the amount of saturated fatty acids and glycerol allows the plasma membranes to remain fluid.

b. Decreasing the amount of unsaturated fatty acids and cholesterol helps in maintaining fluidity.

c. Increasing the amount of unsaturated fatty acids and cholesterol allows the plasma membranes to remain fluid.

d. Increasing the amount of saturated fatty acids and carbohydrates.

Answer 1

The two mechanisms are:

1. Decreasing the amount of saturated fatty acids and glycerol allows the plasma membranes to remain fluid (a).

2. increasing the amount of unsaturated fatty acids and cholesterol allows the plasma membranes to remain fluid (C).

Note: There are two factors which affects membrane fluidity:

i. Temperature

ii composition

Under altered temperature condition, the fatty acid composition of membrane lipids is altered to maintain membrane fluidity. For example, under low temperature synthesis of unsaturated fatty acids is increased. The reason being, that unsaturated fatty acids contain one or more double bonds which help them in bending or forming kink. Because of this bending or kink the phospholipids with unsaturated fatty acid tails are unable to pack themselves tightly resulting in fluid nature of membrane even at low temperature. On the contrary, the saturated fatty acids are able to pack themselves tightly by their straight tails there by decreasing the fluidity of membrane.