Topic 6 Flashcards
Lipids
nonpolar, hydrophobic, insoluble in water
examples of lipids
fatty acids, triglycerols, membrane lipids, chloesterol
fatty acid
long chains of hydocarbon carboxylic acids amphipathic saturated (no double bonds)or unsaturated (double bonds)
double bonds are usually in ___ conformation, why
cis, lowers melting point by introducing kinks in structure
how to name fatty acids
number of carbons: number of double bonds (if trans, put trans here) triangle number at which double bond is
number of cis bonds increase, MP ___
lowers, more liquid are room temp
what affects fatty acid melting point
length and saturation
longer fatty acid tails have ___ MP, shorter have ___
higher, lower
saturated fatty acids have ____ MP, shorter have ____
higher, lower
which one takes precedence? length or unsaturation
usaturation
do cis or trans fatty acid stack better
trans
TAG
tricyglycerol, stores fatty acids, very hydrophobic,
membrane lipids
glycerophospholipds, sphingolipids, cholesterol
glycerophospholipids
strongly amphipathic (large polar group compared to TAG)
Cholesterol
rigid, non-polar, weakly amphipathic, mostly hydrophobic
T/F does cholesterol from membrane alone?
OH associated with polar headgroups and nonpolar portion inside membrane
amphipathic molecules form ___ or ___ in water
micelles (fatty acids) and bilayers (membrane lipids)
liposomes
the spherical vesicles that lipid bilayers form
Bilayers
acyl chain and polar head group, non-covalent, fluid yet stable
Transition temperature ____ artificial membrane
very sharp unlike biological membrane not sharp
DTUS
decreasing temp, more unsaturated, shorter fatty acids
ITSL
increasing temp, saturated, longer fatty acids
cholesterol limits ___
rotational movement, increasing van der walls
cholesterol in low temp
prevents membrane from packing too close
cholesterol in high temp
decreases motion and disorder, increases rigidity
lipids move which way in a membrane
laterally
how can transverse diffusion happen
flipases increase rate of transversion diffusion by specific transport
Types of membrane proteins
Integral, peripheral, lipid linked
integral
hydrophobic interactions, polar on the outside, non polar inside, look like dumbell
peripheral
on the perimeter, electrostatic and polar, easy to separate from membrane,
lipid linked
hydrophobic with lipid prosthetic group anchor
how can the middle portion of peripheral membranes be hydrophobic
they have hydrophobic amino acid tails pointing out on the surface
example of K+ channel
non polar side chains are in the middle and polar on es on the outisde
examples of polar side chain amino acids on the outside
Asp, Glu, Lys, Arg
secondary structures that cross membranes
a-helix (must be 20 or more hydrophobic aa to cross membrane) and beta barrels
Fluid Mosaic Model
lipids move laterally not transverse, limited by cytoskeleton, carbohydrate chains attached to extracellular cellular surface
which molecules diffuse
small non polar molecules
what does rate of diffusion depend on
size of molecule (small move faster), concentration gradient (larger gradient increases rate), lipid solubility (greater solubility rate increases)
passive transport
exergonic, energy released
active transport
energy required, endergonic
if G is -
spontaneous, passive
if G is +
needs energy, non spont
overall G must be ___ for transport to occur
-
what do transport proteins do
reduce activation energy barrier for transport
examples of passive transport
porins and ion channels
porins
beta barrel, water-filled pore in center, trimer, non selective
ion channels
tetramers, channel between subunits, highly selective
K+ ion channel, why does K+ pass through more easily than Na+
cant interact as well as K+ in channel, not about size
Transporter proteins (5)
type of transport protein, do NOT span across membrane, conformational change allows passage, passive or active, selective
curve for passive transport by carrier proteins for velocity vs solute
hyperbolic
carrier proteins are
uni/sym/anti port
primary active transport
uses ATP, selective
secondary active transport
uses ion gradient as source of free energy
Na+K+ ATPase
primary active transporter, concentration gradients generated are used as energy source, electrogenic, antiport
how is activity determined:
by size of concentration gradient
steps of Na+K+ ATPase
1) 3 Na+ enters from inside
2) ATP phosphorylated causing conformational change
3) Na+ released outside
4) 2 K+ comes from outside
5) hydrolysis of Pi causes conformational change
6) K+ released inside
Na Glucose transporter
secondary active symporter
