Question

A cell membrane regulates which substance can enter and leave the cell-based upon their size and polarity. Which mode of cell transport is the movement of water down its concentration gradient?
A. Facilitated diffusion
B. Osmosis
C. Simple diffusion
D. Passive transport
E. Active transport

Answer 1

Hint: In facilitated diffusion, proteins channels present in the cell membrane aids in the transport of molecules into the cell or vice versa. ATP is not required for such diffusion, which is an example of passive transport. Movement of water across the membrane is called osmosis.

Complete answer:
> Osmosis is the movement or diffusion of water molecules across the selectively or semi-permeable membrane, along the concentration gradient. Here, substances move from a region of higher concentration to a region of lower concentration. It is a process that does not require energy in the form of ATP. It occurs in supercritical liquids and even gases.
a) In facilitated diffusion, special proteins are involved in the movement of substances across the membrane of a cell. It occurs without the expenditure of ATP. The transport rate is at the greatest when the entirety of the protein carriers are being utilized. It is an example of passive transport, where substances move from a higher concentration region to a lower concentration region.
b) The movement of molecules from higher concentration to lower concentration is called simple diffusion. It is carried out by the force of hydrogen bonds present between molecules. It also does not require ATP, therefore, it is passive transport. Oxygen, carbon dioxide, etc. are molecules that follow a simple diffusion method to penetrate the cell membrane during the gaseous exchange in the lungs.
 c) Active transport uses energy in the form of ATP to pump molecules against the concentration gradient. Here, substances use energy to move from a lower region concentration to a higher region concentration. Examples include sodium-potassium pumps, endocytosis, exocytosis, etc.

So, the correct answer is option B.

Note: In Plant cells, the cell layer and the membrane of the vacuole, the tonoplast together are significant determinants of the transfer of atoms in or out of the cell.