Passive, Facilitated and Active Transport Flashcards
what is passive transport
movement of biochemicals and molecules across membranes that does not require energy
what does the initial rate of passive transport depend on
the concentration differential across the membrane and the permeability of the cell membrane
what is facilitated diffusion
a type of transport where molecules or ions cross a membrane via transmembrane integral proteins
what is active transport
movement of molecules across membranes that use energy
what is osmosis
spontaneous movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration to equalize solute concentrations
what is osmotic pressure
the pressure required to maintain equilibrium with no net movement of solvent
what molecules can most easily cross a membrane to most difficult
hydrophobic molecules, small uncharged polar molecules, large uncharged polar molecules
what is a channel
a family of biological membrane proteins which allow the passive movement of ions, water, or other solutes to passively pass through the membrane down their electrochemical gradient
what is a transporter
membrane protein involved in the movement of ions, small molecules, or macromolecules
what type of proteins are transporters
integral membrane proteisn
what type of transport do transporters use
either facilitated diffusion or active transport
what is another term for transporting across a membrane done by a transporter protein
carrier mediated transport
Explain the function of Na-K ATPase and how it works
helps maintain the resting potential and regulate cellular volume. it transports 2K+ ions in for every 3 Na+ ions pumped out using ATP
how much energy is the Na+ K+ ATPase responsible for in cell’s energy? neurons?
cells: 1/5
neurons: 2/3
describe the relationship between rate of transport and concentration of transported molecules in simple diffusion
it is linear. rate of transport is proportional to concentration of molecules
describe the relationship between rate of transport and concentration of transported molecules in transporter mediated
exponential. the rate of transport reaches a maximum when transport protein is saturated
what are the 3 ways to drive active transport
coupled, ATP-driven, and light driven pumps
how does coupled transport work
transport of one molecule against a concentration gradient is coupled to another molecule being transported down its concentration gradient
how does ATP-driven active transport work
invovles energy derived from ATP hydrolysis to move a molecule against its concentration gradient
what are light-driven pumps in active transport
uses energy from light in bacteria
what is uniport
simple diffusion where one molecule crosses a membrane through a transport protein
what is symport
2 molecules cross the membrane using a transporter
what is antiport
one molecule goes from the inside of the membrane to the outside and another molecule travels the opposite direction through a transporter
explain how the glucose carrier works
the binding of Na+ and glucose are cooperative. when one binds, the other binds. when both are bound it induces a conformational change in the protein that results in the release of glucose and Na+ into the cytosol
why is the sodium potassium pumps always active
because cells are leaky
what are cell junctions
cell to cell and cell to matrix interactions mediated by extracellular proteins that hold cells together to form tissues
what are the 4 major classes of cell junctions
anchoring junctions, occluding junctions, channel forming junctions (communicating) and signal relaying junctions
what are the types of junctions in occluding junctions and where are they found
- tight junctions (vertebrates)
2. septate junctions (invertebrates)
what are the 2 types of anchoring junctions and what 2 locations are they found in
cell to cell junctions and cell to matrix junctions found in actin filament attachment sites and intermediate filament attachment sites
what are the cell to cell junctions in actin filament attachment sites and intermediate filament attachment sites known as
actin: adherens junctions
intermediate filament: desmosomes
what are the cell to matrix junctions in actin filament attachment sites and intermediate filament attachment sites known as
actin: focal adhesions
intermediate filaments: hemidesmosomes
what are the types of junctions in communicating junctions
gap junctions and plasmodesmata (plants only)
what is the type of junction in signal relaying junctions called
chemical synapses
what are adherens junctions
new cells remain in tissue and are anchored to basal lamina and each other by adherens junctions
what is the role of cadherins in adherins junctions
adherins junctions require ca2+ for cadherin binding. it needs cadherin to bind the cells together
explain how connexins and gap junctions work together
gap junctions are protein “tubes” made of connexin monomers which connect two cells by penetrating the cell membranes of two adjacent cells. it provides a fluid space through which materials can pass from one cytoplasm to the next
