Question

Throughout this course, we explored transport across membranes and how concentration gradients are important in a number of different systems. Compare two types of protein-mediated transport across a plasma membrane. One should require an input of energy the other should not. Describe the two transport processes, explain where energy comes from (if it is needed), and discuss the biological relevance of each of these two processes.

Answer 1

Two types of protein mediated transport are:

(a) Facilitated transport:

Certain hydrophillic molecules find it difficult to pass through the membrane. In that case, their movement through the membrane needs to be facilitated by special integral membrane proteins.

The transport of these molecules occur along the concentration gradient and does not require the input of energy.

Examples: Aquaporins and ion channels

Biological significance: Glucose transport inside RBC

(b) Active transport:

It involves the transport of molecules across the membrane with the help of mobile carrier protein and ATP.

The movement of the materials occur against the concentration gradient and its rate is faster than passive transport.

Examples: Na⁺/K⁺-ATPase

Biological significance: cellular signaling, excretion of toxins/toxic compounds and nutrient uptake