A Closer Look at Cell Membranes

Fluid Moisaic Model

Mixed compositions of phospholipids, glycolipids, sterols and protein

Adhesion Proteins

Help one cell to adhere to another or to a protein.

Communication Proteins

Match up with identical proteins in the plasma membrane of an adjoinning cell.

Receptor Proteins
Cause target cells to change their activity.

Recognition Proteins

They project above the plasma membrane and identify a cell as nonself or self.

Passive Transport

Carries molecules and susbtances from a place of high concentration to a place of low concentration.

Active Transport

Carries molecules and substances from a place of low concentration to a place of high concentration.

Concentration Gradient

Difference in the number per unit volume of molecules of a substance between two adjoining regions.

Diffusion

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

Electric Gradient

Difference in electric charge between adjoining regions.

Pressure Gradient

Difference in pressure exerted per unit volume between two adjoining cells.

Osmosis

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

Hypotonic Solution*

Concentrations with lower solute.

Hypertonic solutions**

Ones having more solutes.

Isotonic Solute

Show no net osmotic movement.

***

Hydrostatic Pressure

Turgor Pressure that is released by any volume of fluid.

Osmotic Pressure

Measure of the tendency of water to follow its water concentration gradient and move into that flow.

Endocytosis

Small patch of plasma membrane balloons inwardsand pinches off the cytoplasm.

Exocytosis

Vesicles move to the cell surface, and then to the protein-studded lipid bilayer.

Phagocytosis

"Cell eating" Common endocytic pathway.

Cell Structure and Function

Nucleoid

Region of the cytoplasm that is not enclosed in a membrane sac.

Lipid Bilayer

Oily, boundary that prevents the free passage of water soluble substances across it.

Wavelenght

Distance from the peak of one wave to the peak behind. Electron Microscopes Magnetic lenses to lend and diffract beams of electrons.

Transmission Electron Microscopes Used to make images of internal details of electrons.

Scanning Electron Microscopes Direct a beam of electrons back and forth across the surface of an element.

Organelles Membrane bonded sacs were eukaryotic cells once started.

Secretory Pathway Series that move polypeptide cells from ribosomes through ER and golgi bodies and release from the cell.

Endocytic Pathway Moves ions and molecules into the cytoplasm.

Vesicles Tiny molecules that move organelles' substances to another organelle in line.

Nuclear Envelope Double membrane system in which 2 lipid bilayers are pressed against each other.

Chromosome Double stranded DNA associated to proteins in a condensed form.

Chromatin Cell's connection of DNA and all proteins.

Peroxisomes Hold enzymes that digest different acids.

Cells junctions Molecular structures where a cell sends or receives signals and materials.

Basal Body Microtubules fixed into a 9+12 array.