cell transport mechanisms Flashcards
what is a fluid mosaic model ?
the fluidity of a membrane and the mosaic arrangement of the proteins give the structure of the membrane
what is a glycoprotein ?
proteins with carbohydrate chains attached
how can a glycoprotein act as a receptor ?
its carbohydrate chain binds to a molecule on the outside of the cell which causes a change in the shape of the tertiary structure and that triggers a a signal that passes through the cell
what is a glycolipid ?
lipid with carbohydrate attached
what does a glycolipids do ?
function in cell communication, stability, cell adhesion, and determining blood type
what are the two functions to a glycoprotein ?
cell signaling and receptors
how does cell signaling work ?
one cell releases a messenger molecule and this molecule travels to another cell the messenger molecule is detected by the cell as it binds to the receptor of the cell membrane
what does cholesterol do ?
it fits between the phospholipid causing them to become more rigid and are packed closer together making the membrane less fluid
what are the components of the phospholipid bi layer ?
hydrophobic tails and hydrophilic heads in a double layered arrangement with the hydrophobic tails facing inwards and and the hydrophilic tails facing outwards
what components can diffuse through a cell membrane ?
small non polar molecules
what four factors does the rat of diffusion depend on ?
concentration gradient - higher difference the faster it is
thickness of exchange surface - thinner it is ( less distance to travel the shorter it is
surface area -the larger the surface area the faster the rate of diffusion
temperature - warmer the temperature the faster the rate of diffusion because there more kinetic energy so more collisions
how does temperature affect the structure of membranes
with increased temperature , there’s more kinetic energy which disrupts the phospholipids and that creates gaps and makes it more permeable
factors affecting rate of diffusion
-the difference in concentrations
-the temperature
-surface area of membrane
what is diffusion ?
the free passage of molecules from a region of their high conc to a region of low conc
passive - no energy
small, non polar, lipid soluble
what are channel proteins ?
a protein that allow the transport of specific substances across a cell membrane
what do carrier proteins do when ions bind to them to transport through the cell membrane ?
changes shape and requires energy
what are two changes to the structure of a membrane that can increase the rate of diffusion through the cell ?
reduced thickness and larger surface area
where do the cells get the energy to diffuse through a cell ?
does not rely on external energy instead relies on the energy created by the random movement of colliding particles
what 2 things does active transport require ?
carrier proteins and energy
how does a carrier protein work ?
changes shape once an ion binds to it in order for it to pass through
endocytosis
movement of materials into cells - phagocytosis
exocytosis
movement of materials out of cells - neurotransmitters
what is the process of phagocytosis ?
surround pathogens
ingest them
take them to food vacuoles
digest them using enzymes in vacuoles
why is facilitated diffusion not a form of active transport ?
it is a passive process and relies on the channel protein to transport the molecules through to the other side of the membrane
what is co transport ?
when the transport of one substance is coupled with the transport of another substance across a membrane
what is active transport ?
the movements of substances across a cell surface membrane against a conc gradient, using energy in the form of ATP
what is osmosis ?
the net movement of water down a water potential gradient through a partially permeable membrane
what is water potential measured in ?
PASCALS
what does it mean if a solution is more concentrated ?
water molecules are less free to move
when there are no dissolved solutes then does the water potential have a greater or lower potential to move ?
highest possible water potential
what is the water potential of pure water ?
zero
the more concentrated solution …
more negative water potential
how is the greater negative water potential of a solution caused by ?
the solutes dissolved in it - osmotic potential
what does the cell do as the turgor pressure is exerted by the plant cell wall ?
the cell takes in water tends to push water out of the cell and therefore would be labelled positive
equation for water potential
turgor pressure + osmotic potential
what happens to an animal cell when put in hypotonic solution ?
there will be a net movement of free water into the cell
- it will swell and burst (lysis) - no cell wall
what happens to a plant cell when put in hypotonic solution ?
- it receives water by osmosis and swells
it does not burst because it is surrounded by a rigid cell wall that can withstand the turgor pressure of the turgid cell contents
what is hypotonic solution ?
where there is higher water potential outside of the cell
what happens to an animal cell when put in isotonic solution ?
no net movement of water
what happens to a plant cell when put in isotonic solution ?
cell will not shrink or swell, as there will not be any change in cells
what is isotonic solution ?
equilibrium
what happens to an animal cell when put in hypertonic solution ?
water flows out of the cell faster than it comes in - crenation (shriveling)
what happens to a plant cell when put in hypertonic solution ?
water from inside the cells cytoplasm diffuses out
what is hypertonic solution ?
higher water potential inside the cell
Describe the structure of a cell membrane
- phospholipid bilayer which it consists of hydrophilic head facing outwards + hydrophobic tail facing inwards
- channel protein to transport molecules
- cholesterol to maintain fluidity
- glycoprotein acts a receptors to allow substances in and out
suggest two properties of molecules that enable them to enter a cell by diffusion
small and non polar
describe one similarity and one difference between facilitated diffusion and active transport
- both use channel and carrier proteins to transport molecules
- active transport uses energy
