In a hypertonic solution, water flows through aquaporins embedded in the plasma membrane of the cell.
This type of transport is best known as which of the following?
A.
Facilitated diffusion
B.
Active transport
C.
Osmosis
D.
Diffusion
The Correct answer and Explanation is:
Correct Answer: C. Osmosis
Explanation:
Osmosis is the movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. This process aims to equalize the concentrations of solute on both sides of the membrane. In the context of cells, osmosis occurs through aquaporins, which are specialized protein channels in the plasma membrane that facilitate the passage of water molecules.
When a cell is placed in a hypertonic solution, the external environment has a higher solute concentration compared to the cytoplasm inside the cell. Water molecules inside the cell will move out through the aquaporins towards the hypertonic environment in an attempt to balance the solute concentrations across the membrane. This outflow of water causes the cell to shrink or crenate, as it loses water.
Facilitated diffusion (Option A) refers to the passive transport of molecules across the cell membrane through carrier proteins or channels, without the use of energy, but this process typically applies to solutes like ions or glucose rather than water.
Active transport (Option B) involves the movement of molecules against their concentration gradient, requiring energy in the form of ATP. Active transport is not involved in the movement of water during osmosis because osmosis is a passive process that does not require energy.
Diffusion (Option D) is the movement of molecules from an area of high concentration to an area of low concentration, but it does not specifically refer to water moving through a membrane. Diffusion applies to gases, solutes, and other particles that move down their concentration gradient.
Osmosis is essential for maintaining cellular homeostasis, and the process is crucial in many biological functions, such as the regulation of fluid balance in tissues, the absorption of water in the intestines, and the control of water content in plant cells. Understanding osmosis helps explain phenomena such as dehydration in animals, where cells lose water when exposed to hypertonic environments, leading to cellular shrinkage and potential disruption of normal cellular functions.