Diffusion is the movement of a molecule from an area of higher concentration to an area of lower concentration.

True or False?

Choice A rationale: Movement of water into the blood from the dialysis solution is incorrect because it is not the main goal of dialysis. Dialysis aims to remove excess water and solutes from the blood, not to add more water to it. The dialysis solution is usually isotonic to the blood, which means it has the same osmotic pressure and does not cause water movement.

Choice B rationale: Simple diffusion across a semi-permeable membrane is correct because it is the process of dialysis. Dialysis is the separation of small molecules from large molecules by using a membrane that allows only the small molecules to pass through. The dialysis membrane is semi-permeable, which means it is selective in what it allows to cross. The dialysis solution contains a lower concentration of wastes than the blood, which creates a concentration gradient that drives the diffusion of wastes from the blood to the solution.

Choice C rationale: Active transport across a semi-permeable membrane is incorrect because it is not involved in dialysis. Active transport is the movement of molecules across a membrane against their concentration gradient, which requires energy and transport proteins. Active transport is not necessary for dialysis, since the concentration gradient is favorable for diffusion.

Choice D rationale: Active transport of glucose from the blood to the dialysis solution is incorrect because it is not beneficial for dialysis. Glucose is a vital nutrient for the body, and it should not be removed from the blood. The dialysis solution usually contains glucose to prevent its loss from the blood by diffusion.

Choice E rationale: Facilitated diffusion across a semi-permeable membrane is incorrect because it is not relevant for dialysis. Facilitated diffusion is the passive movement of molecules across a membrane with the help of transport proteins. Facilitated diffusion is not needed for dialysis, since the wastes are small enough to cross the membrane by simple diffusion.

Choice A rationale: The variant is a term used to describe a viral genome that may contain one or more mutations. It is not related to the difference in concentration between two areas. ³

Choice B rationale: The concentration gradient is the correct term for the difference in concentration between two areas. It is a measure of how steep the change in concentration is. ¹

Choice C rationale: Level gradient is not a term used in biology or chemistry. It may refer to the slope of a surface or a line, but not to the concentration of solutes in a solution.

Choice D rationale: The osmotic pressure is the minimum pressure required to prevent the flow of solvent molecules through a semipermeable membrane. It depends on the concentration of solute particles in the solution and is calculated with the formula π = iCRT. It is not the same as the concentration gradient, although it is related to it. ⁴

Choice E rationale: Turgid pressure is the force exerted by stored water against a cell wall. It is caused by the osmotic flow of water and occurs in plants, fungi, and bacteria. It is also called hydrostatic pressure and affects cell growth, movement, and dispersal. It is not the same as the concentration gradient, although it is influenced by it. ⁵