Question

Which of the following transmembrane proteins consume ATP?

• A. Gated channel proteins
• B. Channel proteins
• C. Carrier proteins
• D. Pumps

Answer 1

The correct option is D Pumps

Special protein channels are transmembrane protein channels which could be any of the following 3 types- channel proteins, gated channel proteins or carrier proteins.

Channel proteins act as pores in the plasma membrane. They form pores called porins. Molecules pass through the pores in the membrane.

Porins are proteins that form large pores in the outer membrane of the plastids, mitochondria and some bacteria, allowing molecules upto the size of small proteins to pass through.
Aquaporins are special channel proteins made up of 8 different types of proteins which transport only water molecules.

Gated channel proteins (GCP) have a gated structure. They have binding sites specific to the molecules being transported across the membrane. Some GCP are also opened by the binding of certain inducers. Such GCP are known as Ligand gated channels. They are stimulated by temperature, chemical stimulus, electrical signals. These can be of various types such as mechanical gated channels, voltage gated channels, ligand gated channels, etc.

Carrier proteins are specific to the molecules that are being bound to and transported. They undergo a conformational change to allow the entry of the molecules into the cell.

Pumps are ATP consuming membrane transport proteins that transport molecules across the membrane against their concentration gradient. For e.g. ${\mathrm{Na}}^{+}-K^{+}$ pumps function by transporting 3${\mathrm{Na}}^{+}$ ions out of the membrane in exchange for bringing 2$K^{+}$ ions into the membrane.