Ch. 5 Membrane Transport Flashcards
What is the function of the cell membrane?
To regulate the exchange of materials between the cytoplasm of the cell and its surroundings
selectively permeable
How do molecules naturally move?
move “down their concentration gradients”
- move until dynamic equilibrium is met
- movement continued because of “Brownian Motion*
2 types of transport
- passive
- active
Passive Transport
movement “down the concentration gradient”
- requires no ATP
- called facilitated diffusion when a transport protein is involved
Active Transport
movement “ against the concentration gradient:
- does require ATP*
- may involve proteins or pumps that pump in both directions at the same time (counter-transport)
processes that result in movement or types of passive transport
- filtration
- diffusion
- osmosis
filtration
movement due to hydrostatic pressure/osmotic pressure (force exerted on membrane by water)
no ATP required
capillary movement
blood pressure forces water, salts, nutrients, and solutes into tissue fluid , while large particles like blood cells and proteins are held back
diffusion
movement of solutes down concentration gradient
requires no ATP
examples:
-movement of O2 from a leaf out into atmosphere
-movement of CO2 out of body
factors that affect diffusion
- temperature
- concentration gradient
- amount of membrane surface area
- membrane permeability
- electrical charge
- pressure gradient
osmosis
diffusion of water across a selectively permeable membrane
- movement of H2O from area of high conc. to low conc.
- movement may be due to pressure gradients
- requires no ATP
Tonicity
in a semi-permeable membrane
defines the concentration of solution across a semi-permeable membrane
- affects ability of the concentration of a solution to affect fluid volume and pressure within a cell
- determines direction water will flow across membrane
3 conditions that refer to concentration of a solute
- hypertonic
- hypotonic
- isotonic
hypertonic
more solute
-may result in a cell shrinking (crenation)
hypotonic
less solute
-may result in a cell splitting (cytolysis)
isotonic
same solute
-still has movement due to Brownian Motion
Sodium potassium pump
regulates the cell volume by “counter-transport”
- produces heat because of energy exchange during phosphorylation
- maintains the proper ‘resting membrane potential’ for nerve and muscle contraction
Vesicular transport
movement of large droplets of fluid/substances into/out of a vesicle
2 types of substances in vesicular transport
- pinocytosis
- phagocytosis
pinocytosis
flow of liquids and materials in bulk
phagocytosis
movement of non-liquid substances
endocytosis
moving into the cell
exocytosis
moving out of the cell
transport of plant cells
-have a contractive vacuole that collects H2O and pumps it out of the cell as necessary
