Question

Does Figure 8.11a show passive or active transport? Explain. (See Concepts 7.3 and 7.4)

Short answer

It is an active transport because solutes are transported from a lower concentration region to a higher concentration region, which requires energy.

Step-by-step solution

Passive transport

Passive transport is a type of transport in which solutes move from a higher solute concentration region to a lower solute concentration across the plasma membrane. For example, the diffusion of oxygen across the air sacs of the lungs is passive transport.

As the solutes move down the concentration gradient in passive transport, it does not require any energy.

Active transport

Active transport is a type of transport in which solutes move from a lower solute concentration region to a higher solute concentration across the plasma membrane. For example, the movement of glucose across the cell is active transport.

In active transport, as the solutes move against the concentration gradient, it requires a carrier protein and energy. The energy needed for active transport is provided by ATP (adenosine triphosphate) molecule.

ATP hydrolysis provides energy for active transport

In the figure, the solute transport is accompanied by ATP hydrolysis. ATP hydrolysis releases a Pi (inorganic phosphate) that attaches to the transport protein in the membrane.

The phosphorylation of the transport protein changes the shape and affinity of proteins. This allows the solutes to move across the membrane protein. ATP is required for solute transport. Thus, it is active transport.