Chapter 4: The Structure and Function of the Plasma Membrane Flashcards
What are the functions of the membrane and describe each! (7)
- compartmentalization - encloses cell boundary and intercellular spaces..each compartment has different contents so specialized activities can occur without interference ..interference = diseases. *Independently regulated.
- framework for biochemical rxns- ensures components are arranged for effective interaction
-ie. all ETC molecules are embedded in MIT M - selectively permeable M - prevents unrestricted exchange of molecules…method of communication (gap junctions in cardiac cells ex)….aquaporins = how water gets into cells.
- transport- substances can be moved up or down [ ] gradient…up= expenditure of ATP….establishes ion gradients
- signal transduction - bind ligands to M receptors…changes internal cellular activities (2nd messenger) ex: cyclic AMP= common messenger
- intercellular interaction - recognition and signalling occurs between cells…ex: immune system!
- energy transduction - one type of energy is converted into another~>..example photosynthesis.. Light+sugar
L> Sugar —>ATP= cellular respiration
Describe the structure of the plasma membrane!
- lipids
- carbohydrates
- ratio of lipid to protein in membrane depends on which membrane , which cell and which organization it is in!
- glycoproteins: carb attached to protein
- glycolipid : carb attached to lipid
Mitochondrial membrane concentration?
- high [] of protein to lipid!
Neuron membrane concentration?
- high [] of lipid to protein
What is between the inner and outer leaflets? Also what the fuck are inner and outer leaflets? (maybe answer in the reverse order)
- inner leaflet is the phospholipids closest to the inside of the cell…outer is closer to the exterior
- between them is a hydrophobic region
What are the three membrane lipids?
- phosphoglycerides
- sphingolipids
- cholesterol
All lipids that make up a membrane are _____
- amphipathic…have a water loving and hating region!
O - hydrophilic region
| \ - hydrophobic region…..
**they aggregate spontaneously in a membrane
Phosphoglycerides:
- ____ and ___ backbone
- phospholipid and glycerol
Phosphoglycerides:
- What are the four major phospholipids?
- choline
- ethanolamine
- serine
- inositool
* phosphatidic acid (base of phospoglyceride)
Phosphoglycerides:
- tail composed of?
- saturated FA and Unsaturated FA
- unsaturated = membrane fluid = not as compact…ie why there is a bend in the tail!
————————–phosphate
choline |
polar head group —-glycerol backbone |========= fatty chain
The polar head group can vary in phosphoglycerides. What are they? (6)
- Dioleoyl Phosphatidic acid
- Phosphatidic acid
- Phosphatidyl-cholne (lecithin) (PC)
- Phosphatidyl- serine (PS)
- Phosphatidyl-ethanolamine (cephaline) (PE)
- Phosphatidyl-inositol (PI)
PC?
- mainly found on the outer leaflet
- important in cell signalling
- some viruses can use it to gain entry into the cell
PE?
- found in cell M mainly of platelets
- important in blood clotting
- promotes membrane curvature
- inner leaflet of M = where it is found
PE and PC?
- neutral phsophoglycerides
- also have EPA ( five double bonds in FA tail) and DHA(6 double bonds in FA tail) aka omega 3’s
L> FA that lowers cholesterol
PS?
- inner leaflet of PM
- flippase are enzymes that ensure they are on the right leaflet
- sign something is wrong if it is on the outer
L> aka cell is not functioning right - prevents memory loss
PI?
- inner leaflet
- cell signalling and emulation of cellular metabolism and growth
Cardiolipin?
- commonly found in the inner mitochondrial membrane
PS and PI have what kind of charge?
- negative
Sphingolipids:
- ceramide molecules??
- sphingosine (sugar) + FA chain
* * sugar containing lipid molecule at the PM surface
Sphingolipids are the most or least abundant lipid in PM?
- least
Sphingolipids:
- ceramide molecules types?
- Sphingomyelin ( ceramide + phosphorylcholine)
- Glycolipid (ceramide + CHO)
L> cerebroside (simple sugar)
L> ganglioside(cluster of sugars)
Sphingolipids
- functions???
- protects PM from harsh exterior …lipid acts a buffer to low pH of other enzymes
- electrical insulation : insulates axons
- cell recognition : cell service receptor
- binds cell to extracellular matrix ..helps it bind so the cell can grow.
-Ceramide function?
- cell signalling
- can be released from PM to act as a signalling molecule for differentiation or proliferation of other cells… Also signal of cell death!
Sphingosine functions in?
signal transduction in PM
Accumulation of Sphingomyelin leads to?
- Niemann pick disease (lysosomal storage disease)
Cerebroside?
L> potential disease associated ?
- Gal + ceramide
- defect in degradation of cerebroside causes organs to malfunction… Gaucher’s disease
L> Type 1 and 2
-type can be helped with an enzyme replacement therapy but for type 2 death occurs by age 2.
Ganglioside?
- GalNac + Gal + Glu + ceramide
|
SiA
- Tay Sachs Disease
L> fatal...build up of lipid in brain...die by age four...homozygous recessive.....
**GM2Ganglioside:
L> GM1 and GM3?
- GM1
L> acts as cell surface receptor
L> influenze, cholera and bothcelism use to gain entry to the cell.
*cholera attaches to GM1
L> cyclic AMP (cAMP) increases in intracellular level of it which leads to an increase in sodium and water loss in the large intestine.
-GM3:
L> lack of it causes neurological diseases ..blindness…seizures etc
Cholesterol:
-__,___ molecules
- flat , rigid
Cholesterol:
-interfere with the movement of?
- FA tails... when present they are not as tightly as packed...making them more fluid 0 |\ | <== cholesterol stiffened region
Plasma Membrane fluidity:
- is affected by?(3)
- number of double bonds in FA tails..
- FA chain length
- cholesterol
Fluid= more double bonds, short FA tails and less cholesterol….. stiff= less double bonds, long FA tails and more cholesterol.
Plasma Membrane fluidity:
- Transition temperature?
- the temp where the membrane movement becomes restricted
What is a micelle?
- bubble or sphere of phospholipids
L> FA tails are in the interior of it~…interior= hydrophobic
what is a liposome?
- double layer (lipid bilayer)
- sphere shape
- inner sphere is hydrophilic
Discuss the spontaneous self assembly of M lipids!
- single layers= micelle
- bilayer = liposome
- liposomes are used to deliver drugs/DNA
L> PROBLEM?
L> drug couldn’t get into the cell…our immune system in the BS detects it before its contents could be delivered (1st Gen liposomes) - 2nd Gen liposomes = stealth liposomes
L> protective layer of polyethylene glycol (low toxicity)
L> antibody in outer membrane ( for cell-cell recognition…aid in reaching the target cell)
L> within the hydrophobic region= lipid soluble drug in bilayer..
L> drug crystallizes in aqueous form in the hydrophilic region.
Membrane CHO’s :
- ___ or ___
glycolipids
glycoproteins
Membrane CHO’s :
- they are on the non-______ membrane side
- cytosolic
aka carbohydrate is on the outside of the PM but if in the mitochondria it will be in the inside not in the cytosol!
Membrane CHO’s :
- ___ composition and structure
- varied
Membrane CHO’s :
- specificity with respect to ?
- molecular interactions
ex: blood….. they have different terminal modifications for O, A and B antigens… - o enzyme is not working and AB have enzymes that modify to have both antigens
Membrane CHO’s :
- membrane is composed of ___% glycolipids and ___% glycoproteins.
10
90
Membrane CHO’s :
- what is the most complex process that can go on?
- addition of carb to a protein
L> important role in cell-cell interactions
L> sorting of membranes into different compartments.
Membrane Proteins:
- three types
- Integral proteins
L> transmembrane aka they go through the membrane completely and if pulled out they would disrupt the membrane. - Peripheral proteins
L> outside the lipid bilayer
L>mobile protein
L> if pulled out it will not disrupt the M - Lipid-anchored proteins
L> covalently linked to a lipid in the M bilayer
L> GP1- glycophosphatidyl inositol
L>main function: adhesion…aka other cells to base membrane…in cancer these are not maintained i.e. metastasizing ..or they are completely removed.
Function of M-proteins:
- Integral
- Peripheral
- Lipid-anchored
- receptors, channels, agents in ETC, enzymes
- anchors, glycocalyx(cell coat), factors in transducing signals, enzymes
- receptors, cell adhesion and enzymes
Dynamic Nature of the PM?
i.e. human and mouse example
- human cell+ addition of sendai (fusing virus regardless of species)
- mouse cell
- two cells fuse
-after 40 mins
the proteins have completely mixed up…its no longer half and half…
Three membrane sections?
- apical plasma membrane (free end of cell)
L> regulation of nutrient and water intake
L>regulated secretion
L> protection - lateral plasma membrane
L> cell contact and adhesion
L> cell communication - Basal membrane
L> cell substratum contact
L> generates ion gradients….base membrane
- hypotonic solution +cell?
- hypertonic solution + cell?
- isotonic solution + cell?
- net water gain..cell swells (taking in water)
- net water loss…cell shrinks (giving up solutes)
- no net loss or gain
