Membrane Composition and Structure Flashcards
Membranes are composed of lipids, proteins, and carbohydrate containing molecules. The carbohydrate portions are covalently bound to either ____ or ____
proteins (glycoproteins) or lipids (glycolipids)
Compounds soluble in organic solvent are called ___
lipids
True or false? the relative amounts of protein and lipid varies from membrane to membrane
true
A membrane that has a high protein to lipid ratio would be found where?
mitochondrial inner membrane
A membrane that has a low protein to lipid ratio would be found where?
myelin
All of the membrane lipids are “amphipathic”. Explain what this means.
one part is hydrophilic: phosphate, amino acid derivatives, and carbohydrate
the other part is hydrophobic: the fatty acid
The head group in membrane lipids is ___, while the hydrocarbon tail is ___
polar; nonpolar
What is different about the hydrocarbon tails in saturated fatty acids than in unsaturated fatty acids?
saturated: tails are straight
unsaturated: tails have kink
Membrane lipids can spontaneously form “____” which are similar to a membrane
liposomes
____ proteins require detergents to separate them from the membrane
integral
Integral proteins interact extensively with the ____ ___ of the membrane
hydrophobic core
Integral proteins usually span the membrane. The membrane spanning domains may also be in the form of ____.
Beta-sheets
___ proteins do not require detergents to separate them from the membrane
peripheral
Plasma membrane is characterized by the greatest amount of ____
cholesterol
Cardiolipin is restricted to ____ membrane
mitochondrial
Plasma membrane phospholipids are found randomly in the membrane. True or false?
false; are not found randomly
PC and sphingomyelin are located primarily in the ____ ____ of the plasma membrane
outer leaflet
___ and ____ are located primarily in the inner leaflet of the plasma membrane
PS; PE
Lateral movement of phospholipids is common, but movement from one leaflet to the other occurs only rarely.. There are enzymes that catalyze the movement of lipid from one leaflet to the other. These enzymes are responsible for maintaining the lipid ____ of the plasma membrane
asymmetry
The _____ portion of glycolipids extends only into the extracellular space. Therefore these lipids are restricted to the outer leaflet of the plasma membrane
carbohydrate
Protein orientation is greatly associated with the ____ of the protein
function
True or false? Proteins in membranes may be anchored by interaction with other cellular elements either outside or inside of the cell.
true
Various regions of a membrane may be associated with a specialized function. These regions may not only have a specific protein composition, but may have a ____ composition which differs measurably from the rest of the membrane
lipid
Bilayer lipids under most physiological conditions can exist in either a _______ phase or in a ___ phase
liquid-crystalline; gel
For any given composition of lipids, there is a temperature at which this phase transition occurs, called the ___ temperature
transition
The lipid bilayer is ___ permeable to small molecules when in the gel phase
less
Unsaturated fatty acids have a ____ melting temperature
lower
Increasing the unsaturated fatty acids in phospholipids ____ the membrane fluidity
increases
One function of cholesterol appears to be to modulate the ____ of the membrane.
fluidity
At temperatures below the Tm, cholesterol ___ the fluidity, and at temperatures above the Tm, it ____ the fluidity
increases, limits
Membrane permeability is simple diffusion, non mediated. This means it is restricted to what type of molecules? give examples
hydrophobic molecules or small uncharged, polar molecules
ex: H2O, O2, CO2, Urea
A channel protein with a water-filled pore is an example of what type of diffusion?
simple
Channel proteins display exquisite ____ in the molecule they allow through the pore
selectivity
Describe facilitated diffusion
proteins do not form pores, but interact with the transported molecule and due to some change in the molecule-protein complex, release the molecule on the opposite side of the membrane
Mediated transport may be classified as electroneutral or electrogenic. Explain each one.
electroneutral: transport results in no difference in charge
electrogenic: transport results in charge difference across membrane
The Na+, K+ ATPase is responsible for transporting ___ Na+ out of the cell, as it transports ___ K+ into the cell at the expense of 1 ATP
3; 2
