Cell membrane structure and transport

Steps:

• Statement 1 correct: Channel proteins form pores enabling water-soluble (polar) molecules to bypass the hydrophobic core of the lipid bilayer.
• Statement 2 correct: Carrier proteins facilitate glucose transport via conformational changes in facilitated diffusion or active transport.
• Statement 3 incorrect: Oxygen diffuses via simple diffusion due to its small size and non-polarity, but the statement wrongly specifies solubility in lipids as the key factor instead of direct bilayer integration.
• Statement 4 correct: Cell surface proteins function as antigens for immune recognition and cell identification.

Why A is correct:

• A includes statements 1, 2, and 4, which accurately reflect facilitated transport mechanisms and protein roles in the fluid mosaic model of membranes.

Why the others are wrong:

• B: Includes incorrect statement 3 about oxygen transport.
• C: Excludes correct statement 4 on protein antigens.
• D: Includes incorrect statement 3 and excludes correct statement 1.

Final answer: A