Question

Which of the following differentiates mammalian cell membrane and plant cell membrane?
A) Plant cell membrane contains chlorophyll, while mammalian membranes do not.
B) Mammalian membranes contain cholesterol, while plant membranes do not.
C) Plant membranes have ion channels while mammalian membranes do not.
D) Mammalian membranes are attached to cytoskeleton while plant membranes do not.
E) Plant membranes contain cellulose while mammalian membranes do not.

Answer 1

Cell membranes are also known as plasma membranes. They enclose the cytoplasm and the nucleus of a cell. It is present in both plant cells and animal cells. However, the cell membranes of plants and animals differ slightly in their constituents.

Complete answer:
Option (A): Chlorophyll is a pigment present in a cell organelle called plastid. It is not present in the cell membrane of plants. Mammals do not have chlorophyll in the cell. Chlorophyll helps in the process of photosynthesis of plants. The main function of chlorophyll is to trap light energy during photosynthesis.
Option (B): Cholesterol is a fat-like substance present in animal cell membranes. It is integrated in the phospholipid bilayer and influences membrane fluidity. It helps to retain membrane fluidity and prevent the freezing of the membrane by inhibiting interactions between fatty acid chains in the cell membrane. Plant membranes lack cholesterol. However, sterols in plants carry out similar functions as the cholesterol in animals.
Option (C): Ion channels are formed by specialized membrane proteins that allow ions to pass through them. They are present in the membranes of all cells, and allow ions of a specific shape and size to pass through. This property is called the selectivity of the channel. Ion channels can be voltage gated, ligand gated or lipid gated. Ion channels are present in both plant and animal cells.
Option (D): Cytoskeleton is a network of similar proteins that extends from the nucleus to membranes of all cells. The proteins of the cytoskeleton are interlinked and help to give shape and mechanical resistance to the cell. Cytoskeleton is present in both plant and animal cells.
Option (E): Cellulose is a polysaccharide present in the cell wall of plants. Since, animal cells lack a cell wall, cellulose is absent in animal cell membranes. Cellulose helps to provide rigidity to the plant cells. Animals obtain the cellulose they need from plant matter. However, humans cannot digest cellulose. They take it in through diet and as roughage. Ruminants like cows, goats can digest cellulose.

Option B is the correct answer.

Note: Cell membranes are present in both plants and animals. The cell membrane is associated with the cytoskeleton and helps to give shape and rigidity to the cells. It also helps to form tissues by attaching to the cell membranes of neighbouring cells. The cell membrane of animals contain cholesterol, while plant cell membrane is lacking in it.