Biological membranes Flashcards
how do cis double bonds effect the melting point
they lower the melting point
length effect on melting point
longer melt at high temps.
shorter melt at lower temps.
unsaturation effect on melting point
saturated = melt at high temp
unsaturated = melts at lower temps.
does length or saturation effect m.p. more?
saturation
membrane lipids (3)
glycerophospholipids, sphingolipids, cholesterol
ordered gel phase
acyl chains pack together in van der waal contact, in gel like soild sate
components of bilayers
acyl chain, polar head group.
disordered gel phase
above trans temp the acyl chains move freely and rapidly
transtion temp
depends on acyl-chain unsaturation and length, when the ordered sate becomes disordered
cold tempatures (effect on membrane)
unsaturated and shorter
hot tempatures (effect on membrane)
saturated and longer
high tempatures (cholesterol)
decreases disorder of acyl chains, increases rigidity
cholesterols effect on membrane fluidity
rigid and planar -limits movment increases van der waal interactions of acyl chains
low tempatures (cholersterol)
prevents close packing between acyl chains
lipid movement
lateral, not transvese
simple diffusion rates depend on what ?
size of moelcule, conc, gradient, lipid solubility
size of molecule (simple diffusion)
smaller moves faster
conc. gradient (simple diffusion)
larger gradient increases rate
lipid solublity (simple diffusion)
greater solublity increases diffusion rate
free energy (delta G) negative
passive transport, spontanous
free energy (delta G) positive
active transport, energy must be provided for reaction to occur
porins and ion channels
passive
proins
trimers, non-selective, water-filled pore in the centre of b-barrel (mostly B-sheets)
ion channels
channel is formed between subunits, highly selective
channel selctivity
depends on the size of the pore and the properties of the side chains/function groups found there
transporter and transport proteins
transporter proteins change conformation transport don’t
Transporter (carrier) proteins
DON’T have membrane spanning pores, change form open on one side to the other, selective, passive or active
carrier proteins kinetic curve
hyperbolic
types of transporter (carrier) proteins
uniport, symport, antiport.
uniport
one being transported
symport
two being transported in the same direction
antiport
two being transported in opposite directions
primary active transporters
typically uses ATP as source of free energy, (delta Greaction less then 0)
secondary active transporters
uses ion gradient as a source of free energy, (delta GTion less then zero)
Na+, K+, ATPase
primary active transporter, the two conc gradient generated across the cell memb. are sued as the source of energy for many seondary active transport processes
Na+ glucose transporter
Na+ transport provides the energy for glucose import
