HRR: membrane transport Flashcards
Differentiate between passive and active transport
passive transport does not require the input of energy while active transport does
Explain how changes in the concentration gradient, surface area, time,
and distance influence diffusional movement of a compound (Fick’s Law
of Diffusion)
concentration gradient: the larger the difference in concentration, the quicker the rate of movement across the membrane
surface area: the larger the surface area, the quicker the rate of diffusion
distance: as it gets larger, there is less flux. a lot of times distance means the thickness of the membrane. the thinner the membrane, the quicker the rate of diffusion.
Define and describe vesicular transport
the movement of substances through the cell membrane via packaging of the substances into lipid membrane vesicles. involves a change in cell shape.
name and describe the types of vesicular transport
endocytosis: bringing things into the cell; pinocytosis, phagocytosis, receptor-mediated endocytosis
exocytosis: removing things from the cell; secretions of molecules or replacing portions of the membrane
transcytosis: moving substances from one side of the cell to another; can be seen in epithelial cells of capillaries
Describe characteristics of carrier‐mediated solute transport across cell
membranes, and name major examples
they utilize structures to help them cross the membrane; examples are seen in passive and active transport
passive: pores, channels, facilitated diffusion
active: symporters, antiporters, pumps
how does water cross the cell membrane?
aquaporins; integrated membrane protein channels that are always open but have high specificity for water. this keeps other molecules from entering via these channels.
define and describe gap junctions
protein channels connecting two cells via large unselective pores. comprised of connexons which are tunnels between cells.
Define gating, activation, and inactivation of ion channels
channel gating: ion channels are controlled by gates that can be open or closed. when open, the ions that the channel is selective for can flow through. the process is passive.
activation and inactivation gates: activation and inactivation gates open and close due to different trigger events or as a function of time. an event can trigger the channel to open the activation gate while the inactivation gate is also open, allowing ions to move down their gradient through the channel. the inactivation gate will eventually close, inactivating the pore. over time, the channel will return to its resting position with the activation gate closed and inactivation gate open.
what are some ways gates of channels are controlled/regulated?
voltage-gated: controlled by changes in membrane potential
second-messenger gated: controlled by concentration of intracellular signaling molecules
ligand-gated: controlled by the binding of hormones or neurotransmitters to receptors
Differentiate between co‐transport and counter transport forms of
secondary active transport systems
both do not not use ATP, but instead use the energy from a solute flowing down its concentration gradient. the other solute being transported is moving against its concentration gradient.
co-transport: also called symporters. all solutes move in the same direction.
counter transport: also called antiporters. solutes move in opposite directions.
Describe how energy from ATP hydrolysis is used to transport ions in primary active transport systems
a phosphate group from ATP binds to the pump, causing a conformational change that helps the movement of solutes.
the interior of a cell is… (negative, positive, or neutral)
negative
___ is primarily found inside the cell, while ___ is primarily found outside the cell (NA vs K)
potassium, inside
describe facilitated diffusion
a carrier-mediated transport; transport of solutes using a carrier that is not always open, as it has various gates that open and close. solute binds to the inside of the carrier, the binding causes the outer gate to close and inner gate to open, and the solute enters the cell. this process can also happen in the reverse.
describe the rates of facilitates vs simple diffusion at various solute concentrations
at lower concentrations facilitated is faster, while at higher concentrations simple will be faster.
