cell membrane + diffusion Flashcards
describe the components of cell membranes 4
-phospholipids
-glycoproteins
-glycolipids
-cholesterol
what is the name of the structure of the cell surface membrane
fluid-mosaic model
how thicc are cell surface membranes
10-20nm
function of membranes 5
- selectively permeable
-to separate organelles
-provide an internal transport system
-isolate enzymes that might damage cell
-provides surface for reactions
give an example of an internal transport system that happens due to membranes
endoplasmic reticulum
give an example of enzymes that might damage a cell
lysosomes with hydrolytic enzymes
what is the fluid above and below the phospholipid bilayer called
above: interstitial fluid
below: cytosolic fluid
why is a membrane a FLUID mosaic model
layers aren’t fixed
layers can slide along
individual phospholipids can rotate
makes it fluid
how to separate phospholipid bilayer
freeze it in liquid nitrogen
fracture layers (split) apart
you can observe using a transmission electron microscope
what is the proof of fluid mosaic model-experiment
you can force 2 separate cells from different animals together
they will fuse into one and separate membrane protein will distribute over larger, new cell
how to identify glycoprotein on a membrane
protein molecules with carbohydrate chains extending from them
how to identify glycolipids
lipid portion with carbohydrate branched out
what is the function of glycoproteins and glycolipids on the cell membrane
the immune system (e.g. lymphocytes) won’t detect the cell as foreign and therefore wont destroy it
how to identify cholesterol on a membrane diagram
groups of hexagons embedded in the bilayer
why is cholesterol found more in animal cells and why does this link to the function
cholesterol makes cell more rigid
animal cells don’t have cell walls so this supplies structure and strength
how to identify an intrinsic protein on a membrane
protein that doesn’t cross entire membrane
role of intrinsic protein
cell signalling using receptors
how to identify extrinsic protein on a membrane
foes across entire protein
another name for extrinsic protein
channel protein
role of channel protein
allows substances to travel into the cell
polar molecules and ions move across the membrane by diffusion
what does glyco mean in glycolipid and glycoprotein
contains sugar
how to identify actin microfilaments
cylinder under phospholipid bilayer in cytoplasm
role of actin microfilament
contract to change the shape of cell
allowing it to manoeuvre easily
why can molecules travel through the phospholipid + examples
Non polar/ non charged molecules are free to diffuse
O2 / CO2
4 factors that increase rate of diffusion
high temperature
short diffusion distance
large surface area
high concentration gradient
rate of diffusion is proportional to equation ( Fick’s law)
(surface area x difference in concentration) / length of diffusion pass
define facilitated diffusion
passive process
no ATP required
aids diffusion
what is the role of transport proteins
transport large molecules/ions across cell membrane that cannot freely pass by aiding movement
describe how transport proteins work
amino acids/sugar bind to protein
causing proteins to change shape
allowing substance through
what is it called when a protein changes shape to allow protein to do its job
conformational change
changing tertiary structure of protein
describe how a sodium-potassium pump works
sodium binds to binding sites in protein
phosphate from atp also binds to protein
protein phosphorolysed changing shape
sodium ions released
potassium ions bind to binding sites
protein dephosphorolysed -changing shape back to original+ releasing phosphate ion
why are sodium ions released
and potassium ions bound
new shape repels sodium ions and attracts potassium ions
what 2 things are used to aid this process
phosphate in ATP for conformational change + energy
electrochemical concentration gradient
define cotransport protein
moving 2 substances with the same protein
