Closer Look at Cell Membranes

Fluid Mosaic Model:
mixed composition of phospholipids, glycolipids, sterols and proteins.

Transport Proteins:

passively let specific solutes diffuse through a membrane spanning channel or actively pump through them.

Receptor Proteins:

bind extracellular substances that can trigger change in cell activities.

Recognition Proteins:

unique identity tags for each species.

Adhesion Proteins:

helps cells of each type locate each other and remain in the proper tissues.

Communication Proteins:

form channels that match up across the plasma membranes of two cells.

Concentration Gradient:

difference in the number per volume of molecules or ions of a substance between two regions.

Diffusion:

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

Electric Gradient:

simply a difference in electric charge between adjoining regions.

Pressure Gradient:

difference in pressure exerted per unit volume.



Osmosis:

diffusion of water across a permeable membrane, to a region where the water concentration is low.

Hypotonic Solution:

fluid with fewer solutes where soluble substances in a membrane differ.



Hypertonic Solution:
the one with more solutes.

Isotonic Solution:

show no net osmotic movement.



Hydrostatic Pressure:

pressure against the wall of a membrane that contains it.



Osmotic Pressure:

measure of the 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 the cytoplasm.

Exocytosis:

vesicles move to the cell surface and the lipid bilayer of its membrane fuses with the plasma membrane.

Phagocytosis:

cell eating common endocytic pathways.



Cell Structure and Function

Nucleoid:

region of the cytoplasm that is not enclosed in a membraneous sac.

Lipid bilayer:

continous, oily boundary that keeps water-soluble substances from getting across it.

Wavelenght:

the distance from the peak of one wave to the wave behind it.

Electron Microscopes:

use magnetic lenses to bend and difract beams of electrons.

Transmission Electron Microscopes:

electrons pass through a specimen to make an internal image of their details.

Scanning Electron Microscopes:
 the passing of beams of electrons back and forth on the surface of a specimen.

Organelles:
bounded sacs.

Secretory Pathway:

moves new polypeptide chains from some ribosomes through ER and Golgi bodies.

Endocytic Pathway:

moves ions and molecules into the cytoplasm.

Vesicles:

tiny sacs that move substances.

Nuclear Envelope:

double membrane system in which two lipid layers are pressed against each other.

Chromatin:

cell's collection of DNA and proteins.

Chromosomes:

double stranded DNA molecules.

Peroxisones:

hold enzymes that digest fatty acids, amino acids and hydrogen peroxide.

Cell Junctions:

structures where cells send or receive materials.

Basal Body:

finished array.

Pseudopods:

false feet.