The cell membrane

Question 1

compartmentalisation

Answer 1

Allows for life
only happened due to plasma membranes

Question 2

Amphipatic lipids

Answer 2

amiphipathic- molecule consisting of a hydrophobic and hydrophilic part

phospholipids are an example of this
structure polar head and fatty acid tail
hydrophillic head and hydrophobic tail

Question 3

Amphipatic lipids hydrophobic collapse

Answer 3

fatty acid of different lipids interact throu hydrophobic collapse the polar head would allow this to take place in water

micelles - one layer of amphipatic lipids
lipid bilayer- two layer
liposome- cicular shape with a lipid bilayer

Question 4

Biological membrane

Answer 4

bilayers define boundaries of cell from outer boundary and internal cell compartment
semipermeable and selective - depend on size of molecule /receptor/gradient
- fluidic -not rigid and allows mobility

Question 5

phospholipid monolayer vs bilayer

Answer 5

in monolayer means inside is completely hydrophobic and water cant enter and also are smaller in size.

in bilayer it can due to the heads facing inwards and outwards

Question 6

lipid composition

Answer 6

varies among biological membranes
main ones cholestrol, glycolipids, phosphatidylserine

Question 7

phospolipids structure

Answer 7

mainly a glycerol backbone, phosphate group and two fatty acid chains

glycerol derivatives- phosphatidylethanolamine
phosphatidylserine - net negative
phosphatidylcholine

sphingosine derivatine- sphingomyelin

all polar

Question 8

Cholesterol

Answer 8

in eukaryotic cells not bacteria
smaller than other phospholipids
smaller head and rigid steroid ring structure and nonpolar hydrocarbon tail

Question 9

glycolipids structure

Answer 9

not major component of mambrane
have a carbohydrate structure on head
galactocerebroside- have galactose bound to head

Question 10

in inner membrane

Answer 10

phospholipids are present in small quantities in the inner membrane PIP2 will be phophorylated by PI3K to PIP3 and back by PTEN

Question 11

membrane fluidity

Answer 11

lateral diffusionm of components
rapid in phospholipids
and transverse diffusion is very slow

Question 12

regulation of membrane fluidity

Answer 12

length and saturation of hydrocarbon tails affects fluidity
longer and higher saturation = less fluidity
temp also increase fluidity
cholesterol content involved but complicated - at warm cholesterol decreases it and at cooler temp in maintains fluidity

Question 13

distribution of lipids in inner and outer layer of membrane

Answer 13

distribution is asymetric
phosphatidylserine and phosphatidylethanolamine are more present in inner - serine creates signalling hubs due to negative charge for proteis such as kinase C
and phosphatidylcholine and sphingomyelin are outter

Question 14

flip flop movement

Answer 14

when cells under go apoptosis membrane is depolarised and thus phospholipids inside are now out side and attracts immune cells.

Question 15

intracellular signalling

Answer 15

conc of PIP2 and PIP3 induces and regulate this

Question 16

how does the cell maintain fluidity under increase in temp

Answer 16

incorparate larger amounts of saturated fatty acids and decrease non saturated

Question 17

how do cells react to hyperthermia

Answer 17

increases migration of cells
WIP is involved in detection of change of temp in immune cells
changes in lipid composition occurs more in wild type then the ones that dont have wip

Question 18

Proteins

Answer 18

trans membrane proteins extend across the bilayer and have either a single alpha helix or multiple helixes or as a rolled up beta sheet and also may include some gobular domains. may also be single or multipass with a fatty acid chain inserted in the cytosolic lipid monolayer

Question 19

functions of membrane proteins

Answer 19

trandporters of ions and small molecules
cell adhesion molecules; cell-cell contact,cell-extracellular matrix contact
receptors for soluble factors; gormone receprors, cytokine receptors
proteins specific for organelle function; electron transport chain and ATp synthase

Question 20

Electrical properties of biological membrane

Answer 20

membrane potential ; voltage across the cell membrane caused by electric charge difference inside and outside due to passive diffusion and pumping by ion channels
ions such as k+,Na+,H+

Question 21

formation of functional domains

Answer 21

planar aggregation - free proteins in lipid layers interact with each other and when interaction is stablised form aggregates
also works with lipids and creates areas with enrichment and exclusion of certain types of lipids

sequestration- areas will favour a more organised protein distrbution and can cause exclusion

extracellular environment could also favour a certain type of interaction and thus effect the proteins in the domain

cytoskeleton - can interqact with certain proteins and also favour them and thus have an effect on protein localisation

Question 22

proteins form functional regions by ?

Answer 22

binding of extracellular domains to the extracellular matrix and/or receptors of neighbouring cells or other proteins within the cell membrane

binding of cytoplasmic domains to cytoplasmic proteins or the cytoskeleton

interaction with lipids; lipid rafts

Question 23

lipid rafts

Answer 23

small specialized discrete areas in membranes rich primarily in sphingolipids and cholesterol where some proteins are concentrated

Question 24

functional polarisation

Answer 24

organisation of domains with different functions
segregation of proteins and lipids by
formation of lipid raft and nano domains
binding of proteins to neighbouring cells
binding of proteins to cytoskeletal points