Question

multiple choice question
in general, ____ molecules move across the plasma membrane readily, whereas ____ molecules need special transport systems to move them across the membrane.

protein; carbohydrate
charged; uncharged
smaller; larger
water; non - water

Explanation:

To solve this, we analyze each option:

• Option "protein; carbohydrate": Both are large and often need transport, so incorrect.
• Option "charged; uncharged": Uncharged (like small non - polar) move easier, charged need transport, so this is reversed, incorrect.
• Option "smaller; larger": Smaller molecules (e.g., O₂, CO₂) can diffuse easily. Larger molecules (e.g., glucose) need special transport (like facilitated diffusion or active transport), this fits.
• Option "water; non - water": Water moves via osmosis, but many non - water small molecules also move easily, so this is incorrect.

Answer:

C. smaller; larger (assuming the options are labeled A, B, C, D with C being "smaller; larger")