second lecture -
every cell at their time window will receive thousands of signals … intrinsic or extrinsic. one way they can repsonse is by receiving those signals but not all signals are recievable it is all about specificitiy. specific proteins are proteins and itneral with signal and then go into the cell and then the cell can either have a quick reponse by modifying their molecules inside or slow/longm temr by cell activiating or repressing a group of genes inside the cell. Product of those gnees will resond to that signal. some signals can respond to both or speicifically to just one.
cell reonse either quck reponse and modifies exisitn protein or moclules
or slow and long term reponse hurs to days by the cell aciving and preseing speicif gene sin the nucleus the product of those genes that are turned on thn cary out the reposne. so its either modify th exisitn proteins to have a quick reponse and carry out the singal or slowluy turn on or off genes and make new proteins to carry out the reposne.
receptors have to activate this process. the cell membrane / the biomemb rane sperating the inside and outside part of the cell. the cell membrane is present at the outer part of he structure - major part is the lipids - lipids are the main component of any biomembrane in our body. . . we have cell bran which serpates golgi, mitochondria. phospholipids are the main type of lipid.
the biomembrane are organized - made by hydrophobic interactions and weak vanderwall there is no covalent ….
head group thaqt is hydrophili and tail is made of carbona and hyrophobic. there is a tendency for the hydrophobic to group together and keep the philic out . organization because of the philic and phobic. the tail has different lengths that are attached to the glycerol molecule. the tails can all be carbon carbon single but some can have double bonds. single bonds - saturated and at least on double bond - unsaturated or poly unsaturated depending on the kinks or double bonds.
phosphoglyceride is a typ;e of phospholipid.
the head group has a charged head. (hydrophilic) /// we have cholesterol . amphiphatic (water lov ing and hating)…
membrane properties - assymetric, semi-permeable and fluid in nature….
cholestorle is amiphathic because (should be phobic) has one charged group which acts a hydrophillic head..
bilayer strucutre is seperated into the cytosolic side or exoplasmic side. twoards the cytosole or the exoplasm. cytoplasmic leaflet and exoplasmic leaflet. plasma membrane has these. .. .
other membranes like the golig membrane. because it is inside the cytoplams of the cell then the outisde is the cytoplamis and the inside of itself is exoplamis . it is switched lol.
some molecules of lipid/jeads are more seen in one side over the other .. when a ligan interacts witha. receptor and that receptor sends it into the interior part of the cell. so the lipids will help transfer the signal. when a cell has to die, apoptosis -
cytosolic side will. move to the exoplamis side. ( the phohsphorlines)… it takes a lot of energy to come the cytoplasmic to the exoplamsi. there ia an energy barrier. hydrophilic head cant go through the hydrophobic region, but flipases witht he help of atp hydrolysis can push those heads to the other side.
if a cell is going to die by apotpsosis and they have phosphatidylserine.
macrophrages will wande r around recognize thei sphosphotylserine and then kill them out of the system/activate apoptosise. If there is a lot on the exoplamis phosphodyle serine will result in cell death.
fluidity - of the lipid bilayer depends on both its composition and temperature.
it is based on the moelcule nmkotion inside the membrane. The nmoclules that are part of the membrane if they move at high speed then that part of the membrane will become more fluid. higher movment = more fluid.
the lipid can move laterallu or rotate in place. if the moelcule moves in a quick direction it will increase fluidity. temperature. higher temperature - more fluid
lipid composition determines fluidity - when u have saturated (single) and willmake a linear structure. and their movement will be restricted. Saturated (long chaings)
if u have a chain with unsaturated or some unsatured then will have double bonds(kinks) will reudce the distence and more fluid.
the longer the chain the less fluid. shorter - more fluid
membrane needs to be fluid because … it needs to let things pass - ions passing
the phosphoserline meolcule has to move or the receptor has to move in order to let the ligan bind. So we need movement. fluid - enhance interaction.
FRAP - floursence recovery after phohobleaching
proteins - on membrane
ions pass through membrane then it requires assistance of the proteins. proteins form some type of channels even water needs these proteins.
transmembrane will go through the bilipid layer. some part will be inside, outside, and the middle
peripheral - loosly attached to the membrane and justsitting on either side of the membrane and will interact with a lipid. head group or another transmembrane protein or another protein.
Lipid anchor proteins that are attached to the memenrane with the help of a covalent linkache of a lipid molecule/chain.
Transmembrane proteins cross the bilayer with a short a helicaln domain. . . two glycophorin proteins need to come together to form a homodimer. it needs two to function. If we have two glycophorin a molcules too far away then they cannot function intill they are close. the fluidity of the membrane will help them get closer.
even proteins cannot pas from one leaf to another. if its transmembrane hey need a mobility to function. if its transmembrane it will have a exoplasmic cite and the cytoplsimic site. and the middle which has amino acids that are hydrophobic.