CELL 1 Flashcards
what does PM of cell look like in electron micrograph
3 layers
- 2 dark layers
- 1 light layer
what molecules make up PM
- lipid molecules
- proteins
what does 1st dark line correspond to
polar regions of lipids and proteins
what does middle light layer correspond to
non polar regions of lipids and proteins
what does 2nd dark line correspond to
polar regions of lipids and proteins
what is a polar molecule
molecule in which distribution of electrons across covalent bond unequal
what does unequal distribution of electrons result in
- pos end
- neg end
what is a non polar molecule
molecule in which distribution of electrons across covalent bond equal
what is major lipid molecule in PM
phospholipid
what are components of phospholipid
- polar / hydrophilic head
- non polar / hydrophobic tail
why is phospholipid amphipathic
has hydrophilic + hydrophobic region
what is attached to glycerol backbone
- polar phosphate group
- 2 non-polar fatty acid chains
how do phospholipids spontaneously arrange themselves in aqueous enviro
- polar head groups interact w water
- non polar tails face away from water
what is conformation of phospholipids (2)
- energetically stabilizing
- favourable
what does layer of hydrophobic tails form
hydrophobic core
what makes lipid molecules that form micells diff from phospholipids
1 HC tail instead of 2
why can’t phospholipids form micells
2 HC tails too bulky to fit in centre
what do fatty acid chains contain
- HC chain
2. carboxylic acid
what do double bonds in fatty acid chains do
put kinks in HC chain
what is result of kinks in fatty acid chains
unable to pack as closely together
what is cholesterol
lipid molecule found in PM
what are 3 components of cholesterol
- steroid ring
- hydroxyl group
- HC side chain
why is cholesterol amphipathic
- HC chain makes it hydrophobic
- OH makes it hydrophilic
how are mem lipids arranged
asymmetrically
what does fluid mosaic model state
- structure of mem dynamic
- globular proteins float in sea of phospholipids
what do carbohydrates attach to in mem (2)
- proteins
2. lipids
what does lipid bilayer give to mem (2)
- fluidity
2. elasticity
what type of proteins does FMM consider (2)
- peripheral mem proteins
2. integral mem proteins
how are integral mem proteins stuck into mem
a. partially
b. completely span bilayer
where do peripheral mem proteins lie
above plane of mem
what do peripheral mem protiens attach to
- proteins
2. lipids
what 2 ideas does FMM focus on
- mem is fluid
2. mem is mosaic
why is PM described as fluid
hydrophobic integral components (lipids + proteins) move laterally
what can limit movement of lipids + proteins
attached to other components
a. in mem
b. inside cell
c. outside cell
how do lipids and proteins move
rotate about long axis
how do lipids move
- flex HC tails
when is rate of phospholipid movement higher
- shorter HC chains ==> less interaction bw adjacent tails
- double bonds bw carbons. ==> phospholipids cannot pack as closely together
what influences fluidity
- saturation of fatty acids
- temp
- cholesterol content
when is mem more fluid
- unsaturated fatty acids
- high temp
- less cholesterol
when is mem less fluid
- saturated fatty acids
- low temp
- more cholesterol
what is cholesterol able to prevent at low temps
crystallization of fatty acids
what is cholesterol able to prevent at high temps
movement of phospholipids
what does fluidity of mem lead to
asymmetry bw outer and inner layers
what does assymetry support
diff fxns of outer and inner layer
what are examples of asymmetry
- outer and inner surfaces have diff proteins
- carbs only in outer surfaces
- outer and inner surfaces have diff phospholipid compositions
what would happen without mem fluidity
- mem proteins would stop functioning
