Passive, facilitaed and active transport Flashcards
(64 cards)
The hydroPHOBIC interior of a lipid bilayer prevents the passage of most polar/nonpolar molecules?
polar
What do cells have that allows for the transfer of specific water-soluble molecules and ions across their membrane?
specialized transmembrane proteins
What are 2 of the major classes of membrane transport proteins?
transporters (carriers or permeases)
channels
All channels and many transporters allow SOLUTES to cross the cell membrane only DOWN a concentration gradient. This process is called:
passive transport or facilitated transport
In which direction do solutes cross the membrane in passive or facilitated transport?
down the concentration gradient
What drives passive transport of a single UNCHARGED molecule and determines its direction?
concentration of each side of the membrane
down concentration gradient = high –> low
What drives the transport of a solute with a NET CHARGE across the membrane?
concentration gradient and the electrical potential difference (aka membrane potential)
The concentration gradient and the electrical gradient combine to form the _______.
electrochemical gradient (or net driving force)
Type of transport that does NOT require the cell to expend energy and involves a substance moving DOWN its concentration gradient
passive transport
Sometimes solutes can moves freely across the lipid portion of the cell membrane directly. Other need assistance of membrane proteins. This process is called:
facilitated diffusion
This type of transport involves solute movement AGAINST their electrochemical gradient.
active transport
What type of transport is coupled to a source of energy, usually ATP hydrolysis or an ion gradient?
active transport
What is active transport mediated by?
transporters
Which type molecules diffuse freely across the lipid bilayer?
hydrophobic molecules (small, nonpolar)
Which molecules diffuse the fastest through the lipid bilayer?
small, hydrophobic (nonpolar) molecules
O2, N2, CO2, benzene are ____ molecules that diffuse (slowly/rapidly) across bilayer
hydrophobic
rapdily
Which molecules diffuse across the bilayer but to a much lesser extent?
small, uncharged polar molecules
Urea, water, glycerol are ____ molecules that diffuse (slowly/rapidly) across bilayer
small, uncharged polar
slowly
Which molecules have very little diffusion across the bilayer?
large, uncharged polar molecules
glucose, sucrose
Which molecules do not diffuse across the bilayer and require active transport or facilitated transport?
ions
What occurs during simple diffusion of molecules in water?
they spread out until there is a uniform concentration of solutes in the solvent
What does diffusion across an artificial lipid bilayer depend on?
nature of molecule
concentration
What does SARS-Cov2 bind to?
ACE2 enzyme receptor on surface of target cell
What happens when SARS-Cov2 binds to receptor on target cell?
facilitates internalization of membrane and dumps intracellular contents into cell which causes an attack on the protein machinery and replicates
