Chapter 8.

Semi-permeable

(of a material or membrane) allowing certain substances to pass through it but not others, especially allowing the passage of a solvent but not of certain solutes.

Diffusion

1. The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration. 2.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.

Vesicle

A bubble-like membranous structure that stores and transports cellular products, and digests metabolic wastes within the cell; an intracellular membranous sac that is separated from the cytosol by at least one lipid bilayer. 2. A small sac or cyst containing fluid or gas.

Carrier protein

A carrier protein is a protein that uses energy in the form of ATP (Adenosine Triphosphate) to move materials in and out of a cell, usually against te concentration gradient.

Passive transport

A kind of transport by which ions or molecules move along a concentration gradient, which means movement from an area of higher concentration to an area of lower concentration.

Active transport

A kind of transport wherein ions or molecules move against a concentration gradient, which means movement in the direction opposite that of diffusion - or - movement from an area of lower concentration to an area of higher concentration. Hence, this process will require expenditure of energy, and the assistance of a type of protein called a carrier protein.

Phospholipid

A lipid with one or more phosphate groups attached to it.

Liposomes

A liposome is a tiny bubble (vesicle), made out of the same material as a cell membrane. Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases.

Fluid-mosaic model

A model that describes the structure of cell membranes. In this model, a flexible layer made of lipid molecules is interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell.

Reverse osmosis

A process by which a solvent such as water is purified of solutes by being forced through a semipermeable membrane through which the solvent, but not the solutes, may pass.

Membrane transport protein

A type of protein that actively transports materials across a plasma membrane that would not otherwise allow this to occur.

Selective transport

All cells are enclosed with a cell membrane. A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport.

Kidney dialysis

Dialysis treatment replaces the function of the kidneys, which normally serve as the body's natural filtration system. Through the use of a blood filter and a chemical solution known as dialysate, the treatment removes waste products and excess fluids from the bloodstream, while maintaining the proper chemical balance of the blood. There are two types of dialysis treatment: hemodialysis and peritoneal dialysis.

Dialysis tubing

Dialysis tubing is a type of semi-permeable membrane tubing used in separation techniques that facilitates the removal or exchange of small molecules from macromolecules in solution based on differential diffusion.

Osmosis

Osmosis is the movement of water molecules through a selectively permeable membrane from higher water concentration to a lower water concentration - or - down a concentration gradient.

Concentration gradient

So a concentration gradient is a measurement of how the concentration of something changes from one place to another.

Surface-area-to-volume ratio

Surface area to volume ratio decreases whenever volume increases, which means the larger an object, the smaller its surface area to volume ratio. For 2 objects of the same volume, however, the more elongated the object, the larger the surface area to volume ratio. That means larger cells will have smaller surface to volume ratios than smaller cells, and elongated cells (such as some nerve cells) will have more surface area than spherical cells of the same volume.

Equilibrium

The condition in which all acting influences are balanced or canceled by equal opposing forces, resulting in a stable system

Phagocytosis

The process of engulfing and ingestion of particles by the cell or a phagocyte (e.g. macrophage) to form a phagosome (or food vacuole), which in turn fuse with lysosome and become phagolysosome where the engulfed material is eventually digested or degraded and either released extracellularly via exocytosis, or released intracellularly to undergo further processing.

Facilitated diffusion

Transport of substances across a biological membrane from an area of higher concentration to an area of lower concentration by means of a carrier molecule. Since the substances move along the direction of their concentration gradients, energy is not required.

Bilayer

a film two molecules thick (formed, e.g., by lipids), in which each molecule is arranged with its hydrophobic end directed inward toward the opposite side of the film and its hydrophilic end directed outward.

Vacuole

a space or vesicle within the cytoplasm of a cell, enclosed by a membrane and typically containing fluid.

Channel protein

channel protein is a protein that allows the transport of specific substances across a cell membrane.

Hydrophilic

having a tendency to mix with, dissolve in, or be wetted by water.

Hypertonic

higher concentration of solute than another

Hypotonic

lower solute concnetration than another

Pinocytosis

mode of endocytosis in which small particles are brought into the cell, forming an invagination, and then suspended within small vesicles.

Brownian motion

n. The random movement of microscopic particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium. Also called Brownian movement.

Receptor-mediated endocytosis

process by which cells absorb molecules (endocytosis) by the inward budding of plasma membrane vesicles containing proteins with receptor sites specific to the molecules being absorbed

Transport proteins

protein that serves the function of moving other materials within an organism.

Isotonic

solution has a solute concentration the same as another.

Hydrophobic

tending to repel or fail to mix with water.

Exocytosis

the transport of material out of a cell by means of a sac or vesicle that first engulfs the material and then is extruded through an opening in the cell membrane

Endocytosis

the transport of solid matter or liquid into a cell by means of a coated vacuole or vesicle