Plasma Membrane Proteins and Cytoskeletal Attachment

Question

Regarding membrane protein functions, which of the following statements is CORRECT?

a. Membrane proteins are responsible for both cell to cell recognition and cell anchoring and are stabilised by linking through to the microtubulele cytoskeletal fibres.

b. A protein that is enzymatically active and membrane-bound will function significantly differently to a protein that is enzymatically active and cytosolic.

c. Membrane proteins are manufactured in the internal cavity (lumen) of the rough ER.

d. Damage to the smooth ER could alter the makeup of the molecules that are displayed at the cell surface.

Regarding membrane proteins, what is incorrect in the statement “Membrane proteins are responsible for both cell to cell recognition and cell anchoring, and are stabilized by linking through to microtubules cytoskeletal fibres"?

I believe this to be wrong due to it normally being Actin Filaments and Intermediate Filaments that attach to Integrin proteins in the cell surface membrane.

Answer 1

a. Membrane proteins are responsible for both cell to cell recognition and cell anchoring and are stabilised by linking through to the microtubulele cytoskeletal fibres.

Not entirely correct as you yourself pointed out that integrins attach to actin filaments.

b. A protein that is enzymatically active and membrane-bound will function significantly differently to a protein that is enzymatically active and cytosolic.

Possible but not necessary.

c. Membrane proteins are manufactured in the internal cavity (lumen) of the rough ER.

They are secreted in the ER and modified there too but not manufactured there.

d. Damage to the smooth ER could alter the makeup of the molecules that are displayed at the cell surface.

Seems correct because the statement itself does not claim certainty. It says that the makeup of cell surface molecules (which could be lipids or proteins) could change in response to SER damage.