AP Bio Cell Membrane

plasma membrane

seperates the living cell from its surroundings. Contros traffic in and out of the cell. Is selectively permeable.

selectively permeable

allows some substances to cross more easily than others.

phospholipids

most abundant lipids

lipids and proteins

main macromolecules in membranes

amphipatic molecules

have hydrophobic and hydrophilic regions

fluid mosaic model

The arrangement of phospholipids and proteins in biological membranes is described by the...

transmembrane proteins

the integral protein completely spans the membrane as...

integral proteins

proteins that penetrate the hydrophobic interior of the lipid bilayer

peripheral proteins

proteins that are not embedded in the lipid bilayer

cell-cell recognition

the ability of a cell to disitnguish one type of neighboring cell from another.

transport proteins

proteins that span the membrane.

channel proteins

transport proteins that have a hydrophilic channel that certain molecules or ions use as a tunnel though the membrane.

aquaporins

channel proteins that facilitate the passage of water

carrier proteins

transport proteins that bind to molecules and change shape to shuttle them across the membrane.

diffusion

movement of molecules of any substance to spread out in available space

concentration gradient

the region along which the density of a chemical substance increases or decreases.

passive transport

transport that requires no energy from the cell to make it happen

osmosis

the diffusion of water across a selectively permeable membrane

tonicity

the ability of a surrounding solution to cause a cell to gain or lose water.

isotonic (animal cell)

if a cell with no cell wall is immersed in an enviroment where there is no net movement of water across the plasma membrane. Stays the same.

hypertonic (animal cell)

when the cell is immersed in a solution where it loses water to its environment, shrivels and probably dies.

hypotonic (animal cell)

when a cell is immersed in a solution, water enters the cell faster than it leaves, it swells and lyses (explodes) like an overfilled water balloon.

osmoregulation

the control of water balance

Paramecium

is a protist that is hypertonic to the pond water in which it lives.

turgid

when the plant cell is very firm, which is a healthy state for most plant cells.

hypotonic (plant cell)

when a plant cell is immersed in a __________ solution the cell contents swell due to osmosis until the elastic cell wall exerts turgor pressure on the cell that opposes further water outake.

isotonic (plant cell)

when a plant cell is immersed in a _______ solution; there is no net movement. The cell becomes flaccid and the plant may wilt.

flaccid

limp, not firm or strong (If a plant is not watered enough, its leaves become droopy and flaccid.)

hypertonic (plant cells)

the plant cell loses water, its volume shrinks. The plasma membrane pulls away from the wall, this is plasmolysis. It is lethal to the cell.

plasmolysis

This happens when a cell shrinks inside its cell wall while the cell wall remains intact. The plasma membrane pulls away from the wall.

facilitated diffusion

the passive movement of molecules down their concentration gradient with the help of transport proteins.

ion channels (gated channels)

Channels that open or close depending on the presence or abscence of an electrical, chemical, or physical stimulus.

active transport

transport that requires the cell to expend metabolic energy and enables a cell to maintain internal concentrations of small molecules. Requires energy.

ATP

supplies energy for most active transport

sodium-potassium pump

transport protein that, translocating the bound solute across the membrane. Exchanges sodium ions (Na) for potassium ions (K) across the plasma membrane of animal cells.

membrane potential

voltage across a membrane. Ranges form -50 to -200 millivolts. The inside of the cell is negative to the outside.

electrochemical gradient

2 combined forces drive the diffusion of ions across the membrane.

electrogenic pumps

special transport proteins that generate the voltage gradient across a membrane.
Ex. sodium potassium pump and proton pumps.

sodium-potassium pump

major electrogenic pump in animals. Restores the electrochemical gradient by setting up a concentration gradient. It pumps 2 K ions for every 3 Na ions that it moves out, it generates a voltage.

proton pumps

the major electrogenic pump. Transports protons out of the cell and transfers positive charge form the cytoplasm to the extracellular solution.

cotransport

single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes in a mechanism.

exocytosis

transport vesicle budded from the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. When the 2 membranes come in contact, the bilayers fuse spill the contents.

endocytosis

a cell brings in biological molecules and particulate matter by forming new vesicles from the plasma membrane.
3 types: phagocytosis, pinocytosis and receptor-mediated endocytosis.

phagocytosis

a cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle.

pinocytosis

molecules are taken up when extracellular fluid is "gulped" into tiny vesicles.

receptor-mediated endocytosis

endocytosis that enables a cell to acquire bulk quantities of specific materials that may be in low concentrations in the environment.

lipoproteins

complexes of proteins and lipids. Cholesterol travels in low density _______

ligands

A molecule that binds specifically to a receptor site of another molecule.

dialysis

movement of particles in a solution through permeable membranes. The diffusion of small solutes through a selectively permeable membrane.