Term
| lipids in membranes (6 types of glyceryl phospholipids) |
|
Definition
cholesterol
sphingolipids (sphingomyelin (SP) and gangliosides)
glyceryl phospholipids:
phosphatidylcholine (PC)
phosphatidlyethanolamine (PE)
phosphatidylglycerol (PG)
phosphatidlyserine (PS)
phosphatidlyinositol (PI)
cardiolipin (CL) |
|
|
Term
| carbohydrates in membranes |
|
Definition
in the form of GLYCOPROTEIN and GLYCOLIPID
NEVER FREE |
|
|
Term
|
Definition
| ball arrangement of amphipathic molecules |
|
|
Term
| which amphipathic arrangement is favored? |
|
Definition
BILAYERS
two fatty acid chains of a phospholipid or glycolipid are too bulky for micelle |
|
|
Term
| how are lipid bilayers cooperative structures (3 things)? |
|
Definition
they are held together by NON-COVALENT interactions (makes them extensive)
they close on themselves; no hydrocarbons exposed; favors COMPARTMENTALIZATION
they are SELF-SEALING; hole energetically unfavorable |
|
|
Term
| what forces stabilize lipid bilayers? which is the primary? |
|
Definition
Hydrophobic interactions (primary)
van der waals - happens between hydrocarbon tails; favors close packing
electrostatic interactions - polar head to water molecules |
|
|
Term
| do the same chemical forces that stabilize protein structures stabilize lipid bilayers? |
|
Definition
|
|
Term
| how can we form liposomes? |
|
Definition
sonicate suitable phospholipids (high freq sound waves)
form 50nm lipid vesicles called liposomes |
|
|
Term
| liposomes are used for... |
|
Definition
water soluble drugs can be put inside and carried into cell
drugs or DNA for gene-therapy may be incorporated into a liposome
they BIPASS BOTH THE CIRCULATION and DIGESTIVE SYSTEM - go directly into cell |
|
|
Term
| how can you solubilize integral proteins? |
|
Definition
| detergent or organic solvent |
|
|
Term
| how can you solubilize peripheral membrane proteins? |
|
Definition
| mild conditions - high ionic strength |
|
|
Term
| what is the most common structural motif for crossing the membrane in integral proteins? |
|
Definition
alpha helices
composed of hydrophobic amino acids
cytoplasmic loops and extracellular loops are composed of hydrophilic aa's |
|
|
Term
| what structural motif are channel proteins made mostly of? |
|
Definition
| beta sheets (barrel form)p |
|
|
Term
| do integral membrane proteins necessarily span the entire lipid bilayer? |
|
Definition
NO
prostaglandin H2 synthetase-1 |
|
|
Term
| prostaglandin H2 synthetase-1 |
|
Definition
its dimerization leads to formation of hydrophobic channel
its substrate is arachidonic acid (hydrophobic)
this protein/enzyme needs to be half inside the membrane because arachidonic acid is generated from hydrolysis of membrane lipids - it is important that the substrate doesn't leave this hydrophobic environment before getting to the enzyme
synthesis inhibited by ASPIRIN |
|
|
Term
| aspirin inhibits what and how? |
|
Definition
| inhibits prostaglandin synthesis by transferring an acetyl group to ser530 of this channel, which blocks substrate (arachidonic acid) access to active site |
|
|
Term
| in what ways can peripheral membrane proteins covalently attach to hydrophobic groups |
|
Definition
cysteine can attach straight to fatty acids
c-terminus can attach to hydrophobic head (such as glycosyl phosphatidyl inositol (GPI) anchor) |
|
|
Term
|
Definition
melting temperature
temp at which half of the lipid molecules are solid and half are fluid |
|
|
Term
| what controls membrane fluidity? |
|
Definition
controlled by fatty acid composition and cholesterol content
# of carbons if have same number of double bonds (higher the #, higher the Tm;low # = more fluid)
presence and # of double bonds greatly decreases Tm |
|
|
Term
| diffusion coefficient (D) |
|
Definition
function of the lipid solubility of the molecule
hydrophilic molecules diffuse more slowly while hydrophobic molecules (steriods fatty acids) diffuse more rapidly |
|
|
Term
|
Definition
Cside1/Cside2
difference in concentration across the membrane
diffusion occurs from a region of higher concentration to a region of lower concentration
for any given molecule, the greater the concentration gradient the greater the rate of diffusion |
|
|
Term
| overall rate of diffusion |
|
Definition
determined by multiplying the diffusion coefficient and the magnitude of the concentration gradient
rate = D x (Cside1/Cside2) |
|
|
Term
| how do we get large polar molecules across the membrane |
|
Definition
can't simple diffusion
use membrane translocation systems (proteins)
passive transport
active transport |
|
|
Term
|
Definition
facilitated diffusion
same direction as concentration gradient - thus, does not require input of energy
ex - acetylcholine receptor: passively transports sodium and potassium ions along their concentration gradients in response to neuronal signals (ligand-gated ion channel) |
|
|
Term
|
Definition
transport goes in opposite direction of concentration gradient - thus, requires energy
ex - sodium-potassium pump: actively exchanges sodium and potassium against their concentration gradients utilizing the energy of ATP hydrolysis
establishes the concentration gradients of sodium and potassium essential for resting membrane potential and thus synaptic transmission |
|
|
Term
| types of channels (passive transport) |
|
Definition
voltage gated
ligand gated
cAMP regulated
other (pressure sensitive) |
|
|
Term
| types of transporters (passive and active transport) |
|
Definition
glucose transporter (passive)
1*-ATPase (Na/K pump)
1*-redox coupled (respiratory chain linked)
ATP-binding cassette (multidrug resistance protein transporter)
2* (Na-dependent glucose transport) |
|
|
Term
|
Definition
ATP hydrolysis used to transport a molecule AGAINST its concentration gradient
ex - Na/K pump |
|
|
Term
| secondary active transport |
|
Definition
gradient of molecule X first established using primary active transport
movement of molecule X back down its concentration gradient then provides energy to drive COTRANSPORT of second solute S against its concentration gradient |
|
|
Term
|
Definition
symport (two molecules in the same direction)
antiport (different directions) |
|
|
Term
| prostaglandin H2 synthase-1 |
|
Definition
half within lipid bilayer
important that this enzyme is within the membrane so that its substrate, ARACHIDONIC ACID, which is a hydrophobic molecule generated by the hydrolysis of membrane lipids, doesn't have to leave the hydrophobic environment of the membrane to reach the active site of the enzyme.
CC - Aspirin blocks prostaglandin synthesis by transferring an acetyl group to ser530 of the channel - blocks substrate access to active site |
|
|
Term
|
Definition
it inhibits prostaglandin H2 synthase-1
blocks active site from arachidonic acid by acetylating Ser530 inside the hydrophobic channel |
|
|
Term
|
Definition
| temperature at which half of the lipid molecules are solid and half are fluid |
|
|
Term
| sarcoplasmic reticulum Ca++ ATPase |
|
Definition
|
|
Term
| what are the 6 steps of calcium movement in the sarcoplasmic Ca++ ATPase |
|
Definition
1. Binding (ATP + 2Ca++ --> SRC ATPase)
2. Phosphorylation
3. Eversion (conformational change)
4. Release (of Ca++ to other side)
5. Hydrolysis (of Pi group on protein)
6. Eversion (change back to original conformation) |
|
|
Term
| what are the side chains that allow K+ to be selected to go down a K+ voltage gated channel |
|
Definition
TVGYG
Threonine
Valine
Glycine
Tyrosine
Glycine |
|
|
Term
| briefly describe the opening/closing steps involved in K+ ion channel |
|
Definition
membrane depolarizes, causing channel change conformation (more + charges move towards ECM while more - charges move closer to cytosol end)
negative charges now on the cytosolic side attract the positively charged ball (INACTIVATION GATE)
ball then binds to and closes the channel - inactivation |
|
|
Term
what are ionophores
give an example of an ionophore
what does it do? |
|
Definition
Valinomycin
ionophores are small molecules that surround ions and shuttle them across membranes, disrupting ion gradients = VERY HARMFUL
ionophores specific for certain microorganisms are potent antibiotics
VALINOMYCIN disrupts K+ gradients; MONENSIN disrupts Na+ gradients |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
