4.1 Flashcards
cell transport mechanisms
which component of the fluid mosaic model is the main transport system in the membrane
integral proteins
what are the 3 passive transport mechanisms
diffusion
facilitated diffusion
osmosis
what are the 3 active transport mechanisms
endocytosis
exocytosis
active transport
define diffusion
movement of particles down the concentration gradient from an area of high concentration to an area of low concentration
define facilitated diffusion
diffusion that takes place through carrier proteins or channel proteins
define osmosis
movement of solvent molecules from an area of high water potential to an area of low water potential down the concentration gradient through a partially permeable membrane
define endocytosis
movement of large molecules into calls through vesicle formation
define exocytosis
movement of large molecules out of the cell through vesicle formation containing molecules within the surface cell membrane
define active transport
movement of substances directly across the membrane requiring energy
what factors effect how a substance is transported
size of molecule
solubility in lipids & water
polarity of the molecule
what are gated channels
protein channels that only open when a specific molecule or electrical charge is present
how do carrier proteins work
picks up a specific molecule
carrier then changes shape so it can move through the membrane
releases molecule on the other side
what is osmotic concentration
measure of the concentration of the solutes in a solution that have an osmotic effect
what is an isotonic solution
when osmotic concentration of the solutes in the solution is the same as that in the cell
what is a hypotonic solution
when osmotic concentration of solutes in solution is lower than that in the cell therefor water moves into the cell
what is a hypertonic solution
when osmotic concentration of solutes in the solution is higher than that in the cell therefore water moves out of the cell
what happens to animal cells when too much water moves out of the cell
cell becomes shriveled and the cytoplasm loses its internal structure
chemical reactions in the cell stop working
what is generated as water enters a plant cell and the cytoplasm swells and presses in the cell walls
hydrostatic pressure
what is pressure potential
the inward pressure exerted by the plant cell wall on the protoplasm of a cell stopping the entry of water by osmosis
what is turgor
when the osmotic force moving water into the plant call is balanced by the pressure potential
what is incipient plasmolysis
when water moves out of the cell so turgor is lost and the cell membrane pulls away from the cell wall as the protoplasm shrinks
How is incipient plasmolysis measured
using serial dilutions looking for the point at which 50% cells plasmolysed 50% not
What is plasmolysis
so much water leaves the cell that the vacuole is reduced and the protoplasm shrinks away from the cell wall
why is most work (experiments) on osmosis osmosis done on plant cells
bigger & easier to see and measure
what is water potential
the potential for water to move out of a solution by osmosis
why is the water potential of pure water zero
the highest water potential water molecules always move from pure water into any solution
what is turgor pressure (P)
the inward pressure exerted by the plant cell wall, force which opposes the entry of water by osmosis
what is osmotic potential
the potential of a solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes
what is the equation for water potential
water potential = turgor pressure + osmotic potential
why is the water potential of an animal cell the same as its osmotic potential
there is no cell wall to exert a hydrostatic pressure
what does active transport allow a cell to do
move substances across membranes against a concertation or electrochemical gradient using ATP
what’s a carrier protein
proteins that move a substance through the membrane in active transport
what does the sodium pump do
moves potassium ions into the cell and sodium ions out
what does the cell surface membrane do
provides control over what moves in or out of the cell
evidence for active transport
-only takes place in living cells
-depends on temperature & O2 concentration
-large number of mitochondria
-poisons that stop respiration or prevent ATPase also stop active transport
define cyanide
metabolic poison that stops mitochondria working
what is phagocytosis
the active process when a cell engulfs something relatively large such as bacterium and encloses it in a vesicle
what is pinocytosis
the active process by which cells take tiny amounts of extracellular fluid into vesicles
why do cells take in extracellular fluid
sources of minerals and nutrients
