cellbio chapter 11 Flashcards
What function do the eukaryotic & prokaryotic membranes do?
they separate the internal contents from external environment
Membranes are selectively permeable, meaning what?
they serve as selective barriers
Whats the general structure of the membrane?
the framework is a phospholipid bilayer
what is found in the membrane that maintains fluidity?
cholesterol
the head and tails of the membrane are what?
amphipathic (meaning both hydrophilic and hydrophobic)
Why does the phospholipid bilayer form a sphere shape?
To avoid a “free edge,” where hydrophobic fatty acids would be exposed to water. it self repairs.
what motions does membrane experience?
- lateral motion of phos.
- rotation of phospholipids
- flexion of fatty acids
- flip/flop of leaflet (barley occurs)
what factors play into fluidity?
- saturated fatty acids favor viscosity
- unsaturated fatty acids favor fluidity
- fatty acid length (shorter) favors fluidity
- fatty acid length (longer) favors viscosity
- temp (higher) favors fluidity
- temp (lower) favors viscosity
what is homeoviscous adaptation?
maintaining optimal fluidity of membranes
all membranes will have a ______ leaflet
cytosolic (faces the cytosol)
non-cytosolic leaflet faces the?
ECF or internal compartment of an organelle
where does the membrane assembly occur?
at the endoplasmic reticulum
where do enzymes bond to the cytosolic surface of?
the ER
the membrane assemble the phospholipids using free what as substrates?
fatty acids
new phospholipids are added to the what of the ER membrane?
cytosolic leaflet
what is a scramblase?
an enzyme that will randomly remove phospholipids and flip them from leaflet to the other
what is the result of a scramblase?
the result is that the ER membrane is a symmetric mixture both leaflets have approximately equal numbers of different phospholipids
what do flipases do? and whats the result?
specifically flip one or two types of phospholipid from one leaflet to the other. result: asymmetric membrane.
glycolipids and phospholipids that have been substituted with carbohydrates are concentrated in the what?
non-cytosolic surface. they end up facing the ECF at PM.
what does integral mean?
directly attached to lipid bilayer
what are the three membrane protein classification?
- transmembrane proteins
- monolayer associated
- lipid linked
what is the role of transmembrane proteins?
they span entire bilayer with regions exposed of ECF and ICF
monolayer associated means
anchored to cytosolic leaflet of bilayer by a amphipathic alpha helix
lipid linked means
solely by a covalently attached lipid molecule
peripheral proteins are?
- bound to integral membrane proteins
- face one side of membrane on the other
in the transmembrane protein structure, portions exposed to ECF or ICF tend to be _______ amino acids
hydrophilic
proteins that span hydrophobic core of membrane that tend to have _______ amino acids
hydrophobic
majority of the bilayer of the transmembrane spanning region are what?
alpha helix
