Question

Identify the incorrect statement about membrane protein.

• A. They all extend from one side of the membrane to the other.
• B. Some serve as channels for ions to cross the membrane.
• C. Many are free to migrate laterally within the membrane.
• D. Their position in the membrane is determined by their tertiary structure.

Answer 1

The correct option is A They all extend from one side of the membrane to the other.

Plasma membrane is the outer covering of all cells but in plant cells, it is present below the cell wall. It is mainly composed of phospholipid bilayer structure with the embedded proteins. There are two types of membrane protein such as external proteins are called extrinsic or peripheral (30 percent of total) while internal proteins are named intrinsic or integral (70 percent of total). Membrane proteins may function as enzymes, permeases, carrier receptors, etc. Few large integral proteins extending from outside to inside are called tunnel proteins or transmembrane protein. They traverse the entire width of the membrane. Singly or in groups, they function as channels for passage of water, ions and other solutes. Ions are charged atoms and are in general hydrophilic. Hydrophilic and water soluble solutes cannot easily pass through a membrane which is essentially bilayer of lipid. Thus, the correct answer is option A.