Ch 3, 3 Membrane transport Flashcards
general functions of plasma membrane
- selectively permeable-only allows certain molecules through
- controls movement of materials in and out- how much and when?
- maintains homeostasis- maintaining sable internal conditions in the body
passive processes
no cellular energy (ATP) is required
substance moves down concentration gradient
passive characteristics
a. its solubility
- lipid soluble(hydrophobic) substances can diffuse through the phospholipid bilayer
- water soluble (hydrophilic) can not, must use channels or carriers
b. its size
- are there channels in the membrane the appropriate size?
- large lipid molecules cannot get through eg. large proteins
c. Presence of suitable carrier proteins in the membrane
- membrane carrier proteins are specific, can only bind to certain molecules
filtration
passive process
-movement against a fluid pressure gradient
materials are carried along with the fluid from a area of high fluid pressure to low fluid pressure
simple diffusion
passive process
- non polar(hydrophobic) substances diffuse directly through the phospholipid bilayer following a concentration gradient
- kinetic energy of the molecules cause them to move, random movement
1. higher conc. higher the rate
2. bigger the molecule, slower the rate
3. higher the temp, higher the rate
facilitated diffusion
passive process, with carriers or channel proteins
certain hydrophilic molecules use specific carrier or channel proteins to pass through the membrane, eg. glucose, amino acids, ions
-this type of diffusion is..
a. specific
b. rate Is determined by number of carriers or channels
c. rate can be regulated
d. substances can only move with a concentration grad. from high to low
using carrier proteins
transmembrane integral proteins transport specific polar molecules (sugars and amino acids)
binding of substrate causes shape change in carrier
using channel proteins
aqueous channels formed by transmembrane proteins selectively transport ions or water
two types-
a. leakage channel-always open
b. gated channels- controlled by chemical or electrical signals
osmosis
passive process
diffusion of water across a selectively permeable membrane
two ways water diffuses through plasma membrane
through the lipid bilayer–wiggles between the phospholipids
through protein channels called aquaporins (AQPs)
water diffusion
from high concentration to low
aqueous diffusion
water concentration depends on solute concentration- the higher the solute conc. the lower the water (solvent) conc.
importance of osmosis
when it occurs, water enters or leaves a cell
change in cell volume disrupts cell function
eg, water enters the cell swells
Tonicity
comparative terms used to describe relative concentration of solutes in two different aqueous solutions
isotonic solutions
2 solutions with the same solute concentration
hypertonic
a solution having a greater solute concentration than another solution
hypotonic
a solutions with a lower solute concentration than some other solution
effects of isotonic on RBC
no change, water moves equally
effects of hypertonic on RBC
cell shrinks
water moves out
loses volume
“crenated”
effects of hypotonic on RBC
water moves in
cell bursts
“lysed”
osmolarity
the measure of the total concentration of all solute particles in a solution
active process
requires carrier proteins (solute pumps)
moves solute against a concentration gradient
requires energy output by cell (ATP)
primary active
energy comes directly from hydrolysis of ATP
causes shape change in transport protein so that bound solutes (ions) are pumped across
eg. sodium/potassium pump
in all plasma membranes..essential for muscle and nerve function
secondary active
depends on ion gradient crated by primary active transport
energy stored in ionic gradients is used indirectly to drive transport of other substances
