Bio Quiz Diffusion

Solvent

1. A liquid in which substances (or solutes) are dissolved forming a solution. 2. In a solution, the solvent is the one that is usually present in greater amount than the solute.

Osmosis

1. Diffusion of a solvent (usually water molecules) through a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. 2. Net movement of water molecules through a semipermeable membrane from an area of higher water potential to an area of lower water potential. 3. Tendency of water to flow from a hypotonic solution (low concentration of dissolved substances) to hypertonic solution (higher concentration of dissolved substances) across a semipermeable membrane Supplement In biological systems, osmosis is essential since many biological membranes are semipermeable, and it leads to different physiological effects. For example, when an animal cell is exposed to a hypertonic surrounding (or lower water concentration) the water will leave the cell causing the cell to shrink.

Diffusion

1. The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration. 2. The spontaneous net movement of particles down their concentration gradient (i.e. difference in the concentrations of substances or molecules between two areas). 3. (Cell biology): a type of passive transport, therefore, it is a net movement of molecules in and out of the cell across the cell membrane along a concentration gradient.

Solute

1. a component of a solution: in a solution, the dissolving substance is called a solvent whereas the dissolved substance is called a solute 2. a substance (usually in lesser] amount) dissolved in another substance. A typical example of a solution is sugar dissolved in water: sugar is the solute and water is the solvent.

Concentration Gradient

1. a gradual change in the concentration of solutes in a solution as a function of distance through a solution. 2. the gradual difference in the concentration of solutes in a solution between two regions. In biology, a gradient results from an unequal distribution of ions across the cell membrane. When this happens, solutes move along a concentration gradient. This kind of movement is called diffusion.

Semi-Permeable Membrane

A membrane that is selectively permeable, i.e. being permeable to only certain molecules and not to all molecules. Supplement An example of such membrane is the cell membrane wherein it allows passage of only certain types of molecules by diffusion and occasionally by facilitated diffusion.

Hypertonic Solution

A solution that has higher osmotic pressure (or has more solutes) than another solution to which it is compared. Supplement When a cell's cytoplasm is bathed in a hypertonic solution the water will be drawn out of the cell and into the solution by osmosis. If water molecules continue to diffuse out of the cell, it will cause the cell to shrink.

Isotonic Solution

One that has the same salt concentration as cells and blood.

Hypotonic Solution

refers to any solution which has a lower osmotic pressure than another solution (that is, has a lower concentration of solutes than another solution) In biology, a hypotonic solution refers to a solution that contains less solute (more water) compared to the cytoplasm of the cell. If the solution surrounding the cell is hypotonic osmosis causes water to have a net flow into the cell, thus, resulting in the swelling and expansion of the cell. When an animal cell is set to a hypotonic environment the cell will eventually lyse (rupture) due to the osmotic pressure. In a plant, the cell will not lyse but become turgid because of its cell wall that prevents it from bursting. In fact, it is the osmotic pressure (or turgor pressure) that helps keep the plant from wilting and losing its shape. see hypertonic solution, the opposite of hypotonic solution