Membrane Transport PPT Flashcards
all materials must pass through the ___ to enter or exit the cell
plasma membrane
plasma membrane is ___
semi-permeable
List 3 ways to transport molecules.
- diffusion through the membrane
- protein transport
- vesicular transport
Transport mechanisms are categorized as either ___ or ___ processes.
passive,
active
Molecules are in ___ random motion.
constant
Molecules are more likely to interact when there is a ___ concentration.
high
difference in the number of molecules between two regions
concentration gradient
Which way will molecules move with a gradient?
from higher to lower concentration
What is molecule movement driven by?
energy in each molecule
the net movement of molecules down a concentration gradient; not affected by the concentration gradient of other molecules
diffusion
List 4 factors that affect the rate of diffusion.
- steepness of concentration gradient
- temperature
- molecule siz
- nature (wind speed/ water currents)
a result of diffusion; the energy of the molecules becomes equal; the molecules continue to move randomly but there is an equal amount of movement in both direction
equilibrium
What can diffuse through the plasma membrane?
small, non-polar molecules;
lipids
What is the most common substance to pass through the plasma membrane?
water
Water can pass through specific water channels in the plasma membrane called ___.
aquaporins
name for water diffusion
osmosis
occurs when water concentration is different on the two sides of a membrane
osmosis
Osmosis is dependent on the concentration of other molecules dissolved in the solution called ___.
solutes
more solutes = less ___
water
the concentration of all molecules dissolved in a solution
osmolarity
ability of a solution to alter the cell’s water volume
tonicity
solution with a higher solute concentration (less water)
hypertonic
solution with a lower solute concentration (more water)
hypotonic
when two solutions have the same solute concentration
isotonic
Water moves from a ___ solution to a ___ solution.
hypotonic,
hypertonic;
(high to low concentration)
If the cell’s fluids are isotonic to the external environment, then ___.
there is no change in cell volume
If the environment is hypertonic, cells with ___. Why?
shrivel,
too much water diffusing out of the cell
If the environment is hypotonic, cells will ___. Why?
burst,
too much water diffusing into the cell
How do large molecules get through the plasma membrane?
transport proteins
transmembrane proteins that act as channels or pores to pass molecules into or out of the cell; each protein will only transport a certain type of molecule
transport proteins
List the 2 types of protein transport.
- facilitated diffusion (carrier/channel)
2. active transport
type of protein transport in which the transmembrane protein will only transport a particular molecule; molecule binds to the protein and is released on the other side of the membrane
facilitated diffusion: carrier
What does the direction of molecule movement depend on in facilitated diffusion?
the concentration gradient;
molecules move from high to low concentration
type of protein transport in which the protein is an “open door”; allows molecules to move in both directions depending on the concentration gradient; usually equalized the concentration
facilitated diffusion: channel
type of protein transport which requires energy from ATP; goes against the concentration gradient (low to high concentration)
active transport
example of active transport
sodium-potassium pump
pumps sodium (Na) out of the cell and potassium (K) into the cell; creates a source of potential energy to do work; expels 3 Na⁺ for 2 K⁺ taken in
sodium-potassium pump
used for bulk transport; move many molecules or single macromolecules into or out of the cell at one time; occurs through vesicles; requires cellular energy (e.g. ATP)
vesicular transport
transport into, across, and then out of cell
transcytosis
transport from one area or organelle in cell to another
vesicular trafficking
vesicle pinches off of the plasma membrane and transports materials into the cell
endocytosis
vesicle forms inside the cell and fuses with the plasma membrane releasing the contents outside
exocytosis
“cell eating”; the material taken up is made up of particles
phagocytosis
“cell drinking”; the material taken up is a liquid
pinocytosis
allows transport of select molecules; molecules bind to specific sites on the plasma membrane; once molecules are in sites the plasma membrane forms a vesicle around them
receptor-mediated endocytosis
