Movement of Solutes and Water Across Cell Membranes

This set of flashcards summarizes key concepts regarding the movement of solutes and water across cell membranes, including diffusion mechanisms, osmotic principles, and transport processes.

What is osmosis in the context of cell membranes?

Diffusion of water across a membrane from an area of higher water concentration to an area of lower water concentration.

What is simple diffusion?

The movement of molecules from one location to another by random thermal motion, usually from areas of higher concentration to lower concentration.

What factors influence the rate of diffusion?

Influenced by temperature, mass of the molecule, surface area of the membrane, and the medium through which diffusion occurs.

What does the term 'net flux' refer to in the context of diffusion?

Difference between the one-way fluxes of molecules in opposite directions across a membrane.

What are the characteristics of facilitated diffusion?

Involves transporters, moves molecules from higher to lower concentrations, does not require energy, and can become saturable.

How is primary active transport different from secondary active transport?

Uses ATP directly to move substances against their concentration gradient, while secondary active transport uses the energy from the movement of another ion (often Na+) down its gradient.

What is the role of aquaporins in osmosis?

Aquaporins are membrane proteins that facilitate the rapid diffusion of water across cell membranes.

What is diffusion equilibrium?

Reached when the concentrations of a substance become equal across a membrane, leading to equal rates of two-way flux.

Define the term 'osmolarity.'

Measure of the total concentration of solute particles in a solution, influencing the water concentration.

What are the three types of endocytosis?

Pinocytosis (cell drinking), phagocytosis (cell eating), and receptor-mediated endocytosis.

How do hypertonic, isotonic, and hypotonic solutions affect cell volume?

Hypertonic solutions cause cells to shrink, isotonic solutions do not change cell volume, and hypotonic solutions cause cells to swell.

What is the Na+/K+-ATPase pump?

Primary active transport protein that moves sodium out of and potassium into cells against their concentration gradients.

What is the relationship between osmolarity and water concentration?

The higher the osmolarity of a solution, the lower the water concentration.