Carrier-mediated transport is also called A. facilitated diffusion B. active transport C. exocytosis D. endocytosis E. phagocytosis. 14. Osmosis can only occur if water travels through the A. cell wall B. semi-permeable membrane C. vacuole D. ER E. cytoskeleton. 15. The type of movement of molecules that is specific and passive, and which becomes saturated if all of the protein carriers are in use is A. exocytosis B. facilitated diffusion C. active transport D. endocytosis E. osmosis. 16. The type of movement that is specific and requires carrier molecules and energy is A. exocytosis B. facilitated diffusion C. active transport D. endocytosis E. osmosis. 17. Cholesterol functions in the plasma membrane to A. transport ions B. serve as an energy molecule C. maintain fluidity D. mediate steroid action E. maintain hypertension
The Correct Answer and Explanation is:
Here are the correct answers:
13. A. Facilitated diffusion
14. B. Semi-permeable membrane
15. B. Facilitated diffusion
16. C. Active transport
17. C. Maintain fluidity
Explanation:
Question 13: Carrier-mediated transport refers to movement of substances across the cell membrane with the help of specific protein carriers. This happens without the use of energy, so the correct term is facilitated diffusion. It allows certain molecules to cross the membrane according to their concentration gradient with the help of carrier proteins.
Question 14: Osmosis is the diffusion of water molecules through a semi-permeable membrane. This type of membrane allows water to pass through but blocks many solutes. It is essential for regulating water balance in cells. The cell wall is rigid and not involved in osmosis, while organelles like the vacuole, ER, and cytoskeleton do not regulate water movement in this way.
Question 15: Facilitated diffusion is a passive process where specific carrier proteins help move substances across the membrane. It does not use energy. However, it can become saturated when all carrier proteins are in use, meaning it has a maximum rate. This is different from simple diffusion, which has no such saturation point.
Question 16: Active transport is a specific process that uses both carrier proteins and energy, usually in the form of ATP. It moves substances against their concentration gradient. This is essential in many physiological functions, such as maintaining ion balances across membranes.
Question 17: Cholesterol is embedded in the plasma membrane and plays a key role in maintaining membrane fluidity. It ensures the membrane is neither too rigid nor too fluid by fitting between phospholipids. This helps cells remain stable and flexible, especially across temperature changes. It is not involved in energy production, steroid action, or blood pressure regulation.
