miércoles, 20 de abril de 2011

A Closer Look at Cell Membranes

Fluid mosaic model: a mixed composition of phospholipids, glycolipids, sterols and proteins.


Transport proteins: let specific solutes diffuse through a membrane-spanning channel in their interior or actively pump them through.

Receptor proteins: bind extracellular substances, such as hormones, that can trigger change in cell activities.

Adhesion proteins: help cells of the same type locate each other and remain in the proper tissues.

Communication proteins: form channel that match up across the plasma membrane of two cells.

Concentration gradient: is a difference in the number per unit volume of molecules (or ions) of a substance between two adjoining regions.

Diffusion: is the name for the net movement of like molecules or ions down a concentration gradient.

Electric gradient: is simply a difference in lectric charge between adjoining regions.
Pressure gradient: is a difference in pressure exerted per unit volume (or area) between two adjoining regions.

Osmosis: is the diffusion of water across a selectively permeable membrane, to a region where the water concentration is lower.

Hypotonic solution: is the one with fewer solutes.

Hypertonic solution: the one that have more solutes.

Isotonic solution: shows no net osmotic movement.
Hydrostatic pressure: turgor pressure.

Osmotic pressure: is one messure of tendency of water to follow its water concentration gradient and move into that fluid.

Endocytosis: a small patch of plasma membrane balloons inward and pinches off inside the cytoplasm.

Exocytosis: a vesicle moves to the cell surface, and then the protein-studded lipid bilayer of its membrane fuses with the plasma membrane.

Phagocytosis: cell eating.

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