Membrane Structure Flashcards
Membranes are composed of ____.
lipids, carbohydrates, and proteins
Membranes function as ____.
physical barriers that define boundaries
What controls the movement of molecules between the inside and the outside of the cell?
proteins
What forms the primary structure of the membrane?
lipids
______ are usually attached to the extracellular membrane surface.
Carbohydrates
All ______ are lipid bilayers with proteins embedded in or associated with the bilayer.
cell membranes
All cell membranes are ____ with _____ embedded in or associated with the bilayer.
lipid bilayers; proteins
____ of the all proteins encoded in the genome are membrane or membrane-associated proteins.
~30%
~30% of the all proteins encoded in the genome are _____.
membrane or membrane-associated proteins
Some signaling pathways depend on _____ or _____ of membrane lipids.
cleavage; phosphorylation
______ depends on composition and temperature.
Membrane fluidity
Membrane fluidity depends on _____ and ______.
composition; temperature
_____ catalyzes flip-flop using ATP.
Flippase
Flippase catalyzes ____ using ____.
flip-flop; ATP
_____ on membrane proteins and lipids are exceedingly important for development, immunological responses, binding of viruses and toxins, and for proper protein folding.
Carbohydrates
Carbohydrates on membrane proteins and lipids are exceedingly important for ______, ______, ______, and _____.
development, immunological responses, binding of viruses and toxins, and for proper protein folding.
All _____ are synthesized in the endoplasmic reticulum (ER).
membrane lipids
All membrane lipids are synthesized in the _____.
endoplasmic reticulum (ER)
The three classes of membrane lipids are _____, _____, and ______.
phospholipids, sphingolipids, and cholesterol
The most common phospholipids are
_____, ______, ______, and _____.
phosphatidylethanolamine (PE), phosphatidylcholine
PC), phosphatidylserine (PS), and phosphatidylinositol (PI
All lipid molecules are derived from _____ except for
_____, which is derived from sphingosine.
glycerol; sphingomyelin
All _____ are derived from glycerol except for
sphingomyelin, which is derived from _____.
lipid molecules; sphingosine
The ____ structure contains a polar hydroxyl group, a rigid steroid ring group, and a hydrocarbon tail
cholesterol
The cholesterol structure contains a ____, _____, and _____.
polar hydroxyl group, a rigid steroid ring group, a hydrocarbon tail
Cholesterol is intercalated among membrane _____.
phospholipids
The interaction of the cholesterol’s steroid ring with the hydrophobic tail of other phospholipids tends to ____ and _____.
immobilize the lipid; decrease fluidity
The interaction of the _____ with the _____ of other phospholipids tends to immobilize the lipid and decrease
fluidity.
steroid ring; hydrophobic tail
Lipids are forced to be straightened by ______.
cholesterol
_____ are forced to be straightened by cholesterol.
Lipids
The thickness of a membrane depends on _____.
the amount of cholesterol
The _____ depends on the amount of cholesterol.
thickness of a membrane
Intracellular membranes have ____ cholesterol than the plasma membranes and are ____ than the plasma membranes.
less; thinner
_____ have less cholesterol and are thinner than
the _____.
Intracellular membranes; plasma membranes
____ charged phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) are more abundant on the internal surface.
Negatively
Negatively charged _____, _____, and _____ are more abundant on the internal surface.
phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI)
PC, sphingomyelin, and glycolipids are more abundant on the _____ surface.
external
____, _____, and ____ are more abundant on the external surface.
PC, sphingomyelin, and glycolipids
We get cholesterol from (1) ____ and (2) ____.
ingestion and uptake; synthesis by the liver
Cholesterol uptake depends on _____.
the low density lipoprotein receptor (LDLR).
There is ____ feedback for cholesterol production.
negative
The first and rate-limiting enzyme in the cholesterol synthesis pathway is ____.
HMGCoA reductase (3-hydroxy-3-methylglutaryl coenzyme A reductase).
Both cholesterol uptake and synthesis are regulated by the ____.
sterol regulatory element binding protein (SREBP)
____, used to lower cholesterol, block the first (rate-limiting) step of cholesterol synthesis.
Statins
Statins work on which step of cholesterol synthesis?
the first step- blocks HMGCoA reductase
Both cholesterol ___ and ____ are regulated by the sterol regulatory element binding protein (SREBP)
uptake; synthesis
____ is a protein containing a transcription factor that regulates both LDLR and all 30 of the synthesis proteins.
SREBP
SREBP is a protein containing a transcription factor that regulates both ___ and ____.
LDLR; all 30 of the synthesis proteins
If cholesterol is ___, the SREBP transcription factor is
released, moves to the nucleus, and activates all these genes.
low
If cholesterol is low, the _____ is released, moves to the nucleus, and activates all these genes.
SREBP transcription factor
The cholesterol level sensor is in the ____, where cholesterol is lowest in the cell and changes would be easiest to detect
ER membrane
The cholesterol level sensor is in the ER membrane, where _____.
cholesterol is lowest in the cell and changes would be easiest to detect
The proteases that cleave SREBP to release the bHLH are located in ____.
the Golgi complex
SREBP must be held in ___ until cholesterol is low; then SREBP must move to ___ where it gets cleaved and the bHLH released.
the ER; the Golgi
SCAP stands for?
SREBP cleavage activating protein
____ binds both SREBP and sterols like cholesterol.
SCAP
SCAP binds both ____ and _____.
SREBP; sterols like cholesterol
Insig binds SCAP when _____ is high.
cholesterol
Insig binds ____ when cholesterol is high.
SCAP
____ binds SCAP when cholesterol is high.
Insig
____, _____, and ____ are in complex when cholesterol is at normal levels.
SREBP, SCAP, Insig
Insig binds SCAP only when cholesterol is ___.
high
___ binds SCAP only when cholesterol is high.
Insig
Insig binds ____ only when cholesterol is high.
SCAP
When Insig binds SCAP, it blocks the ____.
SCAP signaling area.
As cholesterol concentration drops, ___ no longer binds
____ and the complex gets packaged into vesicles to go to the ____.
Insig; SCAP; Golgi
As cholesterol concentration ____, Insig no longer binds
SCAP and the _____ gets packaged into vesicles to go to the Golgi.
dropsSCAP/SREBP complex
One cleavage that releases bHLH cuts SREBP in the ____.
transmembrane domain
One cleavage that releases ___ cuts ____ in the transmembrane domain.
bHLH; SREBP
The cleavage of bHLH from SREBP within the membrane is known as _____.
RIP, regulated intramembrane proteolysis.
___ has been shown to be critical also for Notch signaling in development and for cleavage of the amyloid precursor protein (APP) to produce the bet amyloid peptide in Alzheimer’s disease.
RIP
RIP has been shown to be critical also for _____
in development and for cleavage of the amyloid precursor protein (APP) to produce the beta
amyloid peptide in ____.
Notch signaling; Alzheimer’s disease
When LDL cholesterol levels are less than 100 mg/dl (total plasma cholesterol of 170 mg/dl), heart attacks are ____.
rare
When ____ cholesterol levels are less than ___ mg/dl (total plasma cholesterol of 170 mg/dl), heart attacks are rare.
LDL; 100
Of the roughly 22,000 genes in the human genome, about ____ encode membrane transport proteins and ion channels.
one-tenth (2200)
Of the roughly 22,000 genes in the human genome, about one-tenth (2200) encode ____.
membrane transport proteins and ion channels
A variety of proteins are anchored to the membrane by ____.
glycosylphosphatidylinositol
Glycosylphosphatidylinositol’s function?
anchors proteins to the membrane
____ is found only on the exoplasmic/extracellular face.
Glycosylphosphatidylinositol
Glycosylphosphatidylinositol is found only on the ____.
exoplasmic/extracellular face
