Biomembranes I (Lecture 7) Flashcards
The core of the phospholipid bilayer is ______ and the faces of it are ______.
Hydrophobic
Hydrophillic
True or False: Biological membranes are impermeable to water-soluble molecules and ions.
True
What can you use to measure the lateral diffusion of the phospholipid bilayer.
FRAP
True or False: Heat makes the bilayer more rigid.
False, more fluid
______ face always faces the cytoplasm and ______ always faces the cell exterior or interior lumen.
Cystolic, Exoplasmic
What are the two functions that membrane fluidity and flexibility help with?
Enables organelles to assume their typical shapes
Provides dynamic property that enables membrane budding and fusion
What are the 3 types of phospholipid arrangements:?
Liposome, Micelle, Bilayer sheet
A smaller polar head favours?
inverted micelles or cubic structures
Similar polar head and hydrophobic region favious?
Bilayers
Bulky polar head and only one acyl chain favours?
Micelles
True or False: All phospholipids are amphipathic.
True
True or False: Phosphoglycerides are most common.
True, phosphoglycerides are most common
What are the 3 types of sterols found in animals fungal and plants?
Cholesterol (animals) Ergosterol (fungal)
Stigmasterol (plant)
What is the tripartite structure of nucleotides?
Base + Sugar + Phosphate
What is the tripartite structure of phosphoglycerides?
Head group + backbone + fatty acyl tails
Sphingolipids are attached by what kind of bond?
Amide
True or False: Cholesterols are amphipathic lipids.
True, Polar head group
Tail, conjugated four ring hydrocarbon and short hydrocarbon chain
True or False: Phosphoglycerides, sphingolipids are all sterols.
False, while all phosphoglycerides are phospholipids, only certain sphingolipids are, and no sterols are.
What two lipid components are found mostly in the inner leaflet.
Phosphatidylethanolamine
Phosphatidylserine
Where are phospholipids synthesized?
Cytosolic face of endoplasmic reticulum
What enzyme allows PC (a phospholipid) found in the exoplasmic face of plasma membrane.
Flippases
______ is synthesized on exoplasmic face of Golgi
complex.
Sphingomyelin
True or False: There is more sphingomyelin in ER membrane than golgi membrane.
False, more in golgi and ER membranes
True or False: Cholesterol helps maintain natural fluidity of membranes.
True
______ cholesterol levels the steroid ring separates and disperses phospholipid tails and increases fluidity and at ______ cholesterol level it tends to decrease biomembrane fluidity at typical cholesterol concentrations.
Low, High
True or False: Cholesterol has no effect on membrane thickness.
False, it influences membrane thickness
Small polar head groups have what type of phosphoglycerides?
PE, PS
Similar polar head groups have what type of phosphoglycerides?
PC PG PI
Bulky polar head groups have what type of phosphoglycerides?
Lysolipids
______ are found more in the outer leaflet, ______ are found in both leaflets and ______ are found more in the inside leaflet.
Lysolipids
PC PG PI
PE PS
Where does excess lipid storage occur?
In ER membrane through insertion of triglycerides and cholesterol esters
What are the three types of proteins in the biological membranes?
Integral, lipid-anchored and peripheral proteins
______ are membrane proteins (aka transmembrane proteins) contain one or more hydrophobic membrane-spanning domains.
Integral
Integral proteins are made ip of ______ typical 20-25 amino acids and typically made up of ______ residues
α-helix, hydrophobic
True or False: “Multipass” proteins have multiple transmembrane helices
True
True or False: Polar or charged residues in transmembrane helices need to be sequestered away from the hydrophobic lipid bilayer core
True
______ are made up of B-barrels and are found in outer membrane of gram negative bacteria, mitochondria and chloroplasts
Porins
True or False: The B-barrel has a hydrophilic interior and a hydrophobic exterior.
True
______ are proteins that are bound covalently to one or more lipid molecules.
Lipid anchored
True or False: In lipid anchored proteins, ther lipid may be at the N- or the C-terminus of the polypeptide
True
GPI anchordd is attached to the ______, Prenylation is attached to the ______ and acylation is attached to the ______.
C terminus, C terminal Cys, N-terminal Gly
True or False: Membrane proteins do flip-flop when forming a vesicle.
False, do not flip flop
______ is the word known as the membrane no flip flopping.
Topology
______ proteins do not directly contact the hydrophobic core of the membrane.
Peripheral
What are lipid binding motifs used for?
Degrade damaged/aged
cellular membranes
Generate signaling molecules
