Cell membrane transport, Cell Transport

cell membrane

thin, flexible barrier around a cell; regulates what enters and leaves the cell

phospholipid

A lipid made of a phosphate group and two fatty acids; consists of a hydrophilic polar head and two non-polar hydrophobic tails; forms cell membranes.

lipid bilayer

a thin membrane made of two layers of lipid molecules

hydrophobic

tails of the phospholipid that are repelled by water

hydrophilic

head of phospholipid that attracts water molecules

equillibrium

a condition in which molecules are spread evenly(equally)

Passive transport

the movement of substances across a cell membrane without the use of energy by the cell. Water and Oxygen get through easily. Does not need energy.

Diffusion

movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

how cells regulate their water content

Concentration gradient

the difference in the concentration of molecules across a distance.

osmosis

the process by which water molecules diffuse across a cell membrane from an area of higher concentration to a area of lower concentration.

hypotonic

describes a solution whose solute concentration is lower and water is a higher concentration than inside the cell.

hypertonic

describes a solution whose solute concentration is higher and water concentration is lower than inside the cell.

Isotonic

describes a solution whose solute concentration is equal to the solute concentration inside a cell.

Facilitated diffusion

The transport of substances through a cell membrane down a concentration gradient with the aid of carrier proteins.

Carrier protein

a protein that transports substances across a cell membrane. Then protein is not open at both ends simultaneously.

channel protein

a protein in a cell membrane that extends through the membrane and is open on both ends forming a pore or channel

active transport

the movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy.

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell.

endocytosis

the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell.

exocytosis

the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out.

cholesterol

molecule in the cell membrane that affects it's fluidity

Fluid Mosaic Membrane Model

Description of cell membrane structure in which phospholipids form a bilayer that has a fluid consistency and is embedded with protein molecules.

cell wall

different than a cell membrane; found in plants, bacteria, and fungi (never in animals)

Vesicle

A membrane bound "bubble" or sac that contains materials involved in transport of the cell.

protein channels

proteins in the membrane whose role it is to pass molecules that cannot go through the membrane

semipermeable membrane

A membrane that allows some molecules to pass through but does not allow other molecules to pass through.

ATP

energy

marker proteins

proteins in the cell membrane that identify the cell

with the concentration gradient

from high to low concentration (passive)

against the concentration gradient

from low to high concentration (active)

osmotic pressure

Water pressure

Semipermeable

some substances can pass directly through the cell membrane by passive or active transport

impermeable

not permitting passage

channel proteins

provide corridors that allow a specific molecule or ion to cross the membrane