7.3 Cell Transport Flashcards
most important function of cell membrane is to:
keep the cell’s internal conditions relatively stable
how does the cell membrane keep the cell’s internal conditions relatively stable?
by regulating the movement of molecules from one side of the membrane to the other
diffusion:
the process by which particles move from an area of higher concentration to an area of lower concentration
diffusion is the driving force behind:
the movement of many substances across the cell membrane
If there are more solute on one side of the membrane than on the other, diffusion causes:
a net movement of solute particles from the side of the membrane with the higher solute concentraion to the side with the lower concentration
Once equilibrium is reached:
solute particles continue to diffuse across the membrane in both directions but at apporximatley equal rates so there is no net change in solute concentration
Facilitated diffusion:
the process in which molecules that cannot directly diffuse across the membrane pass through special protein channels
both types od diffusion do notL
require any additional use of the cells energy
aquaporins:
water channel proteins that allow water to pass through them into the cell
osmosis:
the diffusion of water through a selectively permeable membrane
isotonic:
when 2 solutions become the “same strength” (equal
hypertonic:
“above strength” or more solute
Hypotonic:
“below strength” or less solute
osmotic pressure is a force
a force produced by the net movement of water out of or into a cell (driven by differences in solute concentration)
osmotic pressure can cause an animal cell:
in hypertonic solution to shrink, and one in hypotonic solution to swell
Cells are almost always hypertonic to:
fresh water because of the many dissolved molecules in them, causing a cell in fresh water to swell and the cell may burst
In plant cells osomotic pressure cause:
the central vaculoe to shrink and swell
when cells do come in contact with fresh water:
some lack water channels or have cell walls to protect
what prevents our cells from bursting?
surrounded by isotonic fluids like blood
What is active transport?
the movement of materials against a concentration differnece (requires a lot of energy)
For molecular transport (small molecules and ions) against a concentration gradient:
Carried across membrane by proteins in the membrane that act like pumps, protein changes shape to move calcium, potassium, sodium
For bulk transport (large molecules and solid clumps) against a concentration gradient:
Endocytosis and exocytosis
Endocytosis:
the process of taking material into the cell by means of infoldings or pockets of the cell membrane (the pocket that results breaks loose from the outer portion of the cell membrane and forms a vesicle in the cytoplasm)
Phayocytosis:
a type of endocytosis, extentions of cytoplasm surrond a particle and packages it within a food vacuole
