transport across cell membrane Flashcards
what are the 4 functions of the cell surface membrane
separating the contents of the cell from the outside environment
allows different conditions to be established in and out of the cell
regulates transport of materials
cell signalling and recognition
name the different parts of a phospholipid
1 glycerol joined to 2 fatty acid by a ester bond
1 phosphate group
hydrophobic tail
hydrophilic head
how wide is a cell surface membrane
7nm
what are the functions of the phospholipids in a cell surface membrane
to allow lipid soluble substances to come and go
to prevent water soluble substances from coming and going
make the membrane flexible and self sealing
what is an intrinsic protein and what are their functions
proteins which run all the way through the cell surface membrane
carrier proteins are used for active transport
channel proteins are used for facilitated diffusion
what is the function of a glycoprotein and where are they found
they are extrinsic proteins on the outer side of a cell surface membrane and have a receptor site linked to cell signalling
what are glycolipids function and where are they found
found on the outside and are used for cell recognition and informing other cells
what is the function of cholesterol in the cell surface membrane
regulates membrane fluidity
(stops them from melting or freezing)
why is a cell surface membrane a fluid mosaic pattern
it moves but is made up of tiny peices
what is transported by facilitated diffusion
water soluble molecules
charged molecules
glucose
what is transported by diffusion
lipid soluble molecules and gases
where does osmosis and diffusion occur in the membrane
through phospholipids
what is the definition of diffusion
net movemnet of molecules or ions from a region of high conc to low conc
how does conc gradient effect the rate of diffusion
larger the gradient the faster diffusion happens
how does the surface area affect rate of diffusion
larger SA = faster diffusion
how does length of pathway effect rate of diffusion
thinner membrane = quicker diffusion
how can you increase the permeability of the cell membrane to water
increase the number of solutes
add aquaporins
how do channel proteins help facilitated diffusion
they have aquaporins which are linned with hydrophillic amino acids and filled with water to increase the permeability of the cell surface membrane
what happens to a carrier protein when the molecule is trying to go through the membrane
the molecule binds to the protein by hydrogen bonds. the protein then changes shape and rotates to deposit the molecule on the other side
what is a solute
something dissolved in water
what is a solvent
liquid dissolving a solute
what is a solution
mixture of solute and solvent
what is low water potential
a high conc of other particles in the water which could be making bonds
what is a high water potential
closer to pure water
where does water move to in osmosis
from from high water potential to low water potential
(to a more negative area)
what does hypertonic mean
high solute and low water potential
what does hypotonic mean
low solute and high water potential
what happens when water moves into a plant cell
it swells and becomes turgid
what happens when water leaves a plant cell
it shrinks and becomes plasmolysed
what happens to a plant cell in a isotonic solution
no change
the cell is incipient plasmolysis
what happens when water moves into an animal cell
it swells and burst
what happens when water leaves an animal cell
it shrivels and crenates
what is the definition of active transport
net movement of molecules or ions from a low to a high concentration
what does active transport need in order to work
atp
carrier proteins
explain the sodium potassium pump
3 Na ions from inside the cell bind to the carrier protein
atp hydrolysis releases energy and one phosphate ion attaches to the proetien
the protein changes shape and releases the Na on the outside of the cell
2 K ions bind to the protein
phosphate group is released causing the protein to change shape
2 k ions are released into the cell
why is atp hydrolysis important to active transport
because breaking down atp into adp and a phosphate group releases energy which allows the carrier protein to change shape
what is exocytosis
the fusion of a vesicle and a cell surface membrane to allow particles out of the cell
what is endocytosis
the cell surface membrane folds in and surrounds particles from outside the cell the vesicle pulls them in to cell and the lysosomes break them down
what are villi and microvilli
villi are finger like projections inside the small intestine with are covered in microvilli which make up the brush border
they increase surface area
how does a large surface area help the exchange of materials across the villi
more carrier proteins so increased rate of facilitated diffusion
how does a thin wall help the exchange of materials across the villi
short diffusion pathway
how does a good blood supply help the exchange of materials across the villi
helps maintain the concentration gradient
what does the lacteal do in a villi
takes large triglycerides which are too big to be absorbed by the capillary
what happens in co transport in the small intestine
active transport of sodium ions out of the gut cells into the blood
this creates a conc gradient between the cell and the blood
the carrier proteins take the sodium ions down the conc gradient via diffusion with glucose
this increases glucose conc in the cell which then diffuse into the blood via facilitated diffusion
water enters the cell via osmosis and leaves into the blood via osmosis
