Molecular Biology Ch. 5

plasma membrane

-made of a phospholipid bilayer
-selective permeability: allows some substances to cross the membrane more easily than others.
-a fluid mosaic model: phospholipid (fluid) + protein (mosaic)
-selective permeability allows constant regulation of ions.
-hydrophobic molecules can pass b/c the core of the bilayer is hydrophobic. hydrophilic require the use of proteins in order to pass (h20+ glucose, polar molecules)

fluid membranes

1. unsaturated fatty acid chain
2. cholesterol- prevents stacking of membrane at low temperature

peripheral protein (membrane protein)

not embedded in bilayer, loosely bound to the surface of the membrane.

integral protein (membrane protein)

-embedded in bilayer.
-6 types: transport, enzyme activity, signal transduction, cell-cell recognition, intracellular joining, attachment proteins

transport proteins (integral protein)

-transport material across the membrane
-2 types: channel and carrier
-carrier undergoes conformational change once it accepts material

conformational change

the change in shape once a protein accepts material, a process which requires energy (ATP)

enzyme activity protein (intergral protein)

carry out enzymatic reactions

signal transduction protein (integral protein)

the binding site is exposed on the cell surface, the material binds, the protein undergoes conformational change, then sends a signal to the cell to turn on/off some action.

cell-cell recognition protein (integral protein)

helps cell to recognize "friendly" material

intracellular joining protein (integral protein)

tight junctions, desmosomes, gap junctions

attachment proteins (integral protein)

integrins

passive transport

-diffusion across the membrane w/o energy expenditure
-proteins invol.: 1. channel protein (aquaporin, H20 transport. ion channel, open upon electrical/chemical stimulus, gated ion channel) 2. carrier protein (allow transport down the gradient, conformational change)

diffusion

-the tendency of molecules to spread out evenly.
-the rule of diffusion: substances will diffuse from concentrated to unconcentrated area.
-concentration gradient: high to low concentration
-osmosis: the diffusion of water

tonicity

the ability of a solution to cause a cell to gain/lose water

hypertonic

cell is placed in a solution of high solute concentration, causing the cell to shrink.

isotonic

-same concentration of solute in and out of the cell.
-equilibrium: an isotonic environment

hypotonic

cell is placed in a solution that has less solute concentration than itself, causing the cell to swell w/ water

osmoregulation

the cell's ability to regulate solute concentration. Contractile vacuoles carry out this task in protists

water concentration in cells

HYPOTONIC: animal cells, lysed. Plant cells, turgid

ISOTONIC: animal cells, happy. plant cells, shrunken.

HYPERTONIC: animal cells, shriveled. plant cells, plasmolysis

facilitated diffusion

passive transport by way of proteins, no energy !

ATP

-adenosine triphosphate
-energy coupling: the use of an exergonic RXN to drive a endergonic RXN

exergonic

gives off energy

endergonic

absorbs energy

phosphorylated

a molecule bound to a phosphate in motor proteins is taken by ATP to become ADP.

active transport

-transport across the membrane using energy (ATP)
-electrogenic pump (main pump in animal cells): Na+ - K+ pump (major electrogenic pump variety)