Question

Which does NOT require a transport protein to go across endothelial cell's plasma membrane in the capillary wall? Explain why.

(A) cholesterol
(B) glucose
(C) Na+

Answer 1

*Glucose cannot be transported without the help of transport protein as it cannot undergo simple diffusion through the lipid membrane.

There are two types of glucose transpoters which helps in the movement of glucose are 1.Sodium- glucose linked transporters:- it is a symport( transport in the same direction) glucose in conjunction with sodium ions. 2. Facilitated diffusion glucose transporters:-glucose is transported across the plasma membrane by facilitated diffusion mechanism.

*Cholesterol doesn't need any transport protein during the vesicular transport as the 50-90% of plasma membrane is made up of lipids helps in the easy transfer of cholesterol . The transport proteins may be needed for non vesicular cholesterol transport.