Membrane Structure

Question 1

Membranes are composed of ____.

Answer 1

lipids, carbohydrates, and proteins

Question 2

Membranes function as ____.

Answer 2

physical barriers that define boundaries

Question 3

What controls the movement of molecules between the inside and the outside of the cell?

Answer 3

proteins

Question 4

What forms the primary structure of the membrane?

Answer 4

lipids

Question 5

______ are usually attached to the extracellular membrane surface.

Answer 5

Carbohydrates

Question 6

All ______ are lipid bilayers with proteins embedded in or associated with the bilayer.

Answer 6

cell membranes

Question 7

All cell membranes are ____ with _____ embedded in or associated with the bilayer.

Answer 7

lipid bilayers; proteins

Question 8

____ of the all proteins encoded in the genome are membrane or membrane-associated proteins.

Answer 8

~30%

Question 9

~30% of the all proteins encoded in the genome are _____.

Answer 9

membrane or membrane-associated proteins

Question 10

Some signaling pathways depend on _____ or _____ of membrane lipids.

Answer 10

cleavage; phosphorylation

Question 11

______ depends on composition and temperature.

Answer 11

Membrane fluidity

Question 12

Membrane fluidity depends on _____ and ______.

Answer 12

composition; temperature

Question 13

_____ catalyzes flip-flop using ATP.

Answer 13

Flippase

Question 14

Flippase catalyzes ____ using ____.

Answer 14

flip-flop; ATP

Question 15

_____ on membrane proteins and lipids are exceedingly important for development, immunological responses, binding of viruses and toxins, and for proper protein folding.

Answer 15

Carbohydrates

Question 16

Carbohydrates on membrane proteins and lipids are exceedingly important for ______, ______, ______, and _____.

Answer 16

development, immunological responses, binding of viruses and toxins, and for proper protein folding.

Question 17

All _____ are synthesized in the endoplasmic reticulum (ER).

Answer 17

membrane lipids

Question 18

All membrane lipids are synthesized in the _____.

Answer 18

endoplasmic reticulum (ER)

Question 19

The three classes of membrane lipids are _____, _____, and ______.

Answer 19

phospholipids, sphingolipids, and cholesterol

Question 20

The most common phospholipids are

_____, ______, ______, and _____.

Answer 20

phosphatidylethanolamine (PE), phosphatidylcholine

PC), phosphatidylserine (PS), and phosphatidylinositol (PI

Question 21

All lipid molecules are derived from _____ except for

_____, which is derived from sphingosine.

Answer 21

glycerol; sphingomyelin

Question 22

All _____ are derived from glycerol except for

sphingomyelin, which is derived from _____.

Answer 22

lipid molecules; sphingosine

Question 23

The ____ structure contains a polar hydroxyl group, a rigid steroid ring group, and a hydrocarbon tail

Answer 23

cholesterol

Question 24

The cholesterol structure contains a ____, _____, and _____.

Answer 24

polar hydroxyl group, a rigid steroid ring group, a hydrocarbon tail

Question 25

Cholesterol is intercalated among membrane _____.

Answer 25

phospholipids

Question 26

The interaction of the cholesterol's steroid ring with the hydrophobic tail of other phospholipids tends to ____ and _____.

Answer 26

immobilize the lipid; decrease fluidity

Question 27

The interaction of the _____ with the _____ of other phospholipids tends to immobilize the lipid and decrease fluidity.

Answer 27

steroid ring; hydrophobic tail

Question 28

Lipids are forced to be straightened by ______.

Answer 28

cholesterol

Question 29

_____ are forced to be straightened by cholesterol.

Answer 29

Lipids

Question 30

The thickness of a membrane depends on _____.

Answer 30

the amount of cholesterol

Question 31

The _____ depends on the amount of cholesterol.

Answer 31

thickness of a membrane

Question 32

Intracellular membranes have ____ cholesterol than the plasma membranes and are ____ than the plasma membranes.

Answer 32

less; thinner

Question 33

_____ have less cholesterol and are thinner than | the _____.

Answer 33

Intracellular membranes; plasma membranes

Question 34

____ charged phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) are more abundant on the internal surface.

Answer 34

Negatively

Question 35

Negatively charged _____, _____, and _____ are more abundant on the internal surface.

Answer 35

phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI)

Question 36

PC, sphingomyelin, and glycolipids are more abundant on the _____ surface.

Answer 36

external

Question 37

____, _____, and ____ are more abundant on the external surface.

Answer 37

PC, sphingomyelin, and glycolipids

Question 38

We get cholesterol from (1) ____ and (2) ____.

Answer 38

ingestion and uptake; synthesis by the liver

Question 39

Cholesterol uptake depends on _____.

Answer 39

the low density lipoprotein receptor (LDLR).

Question 40

There is ____ feedback for cholesterol production.

Answer 40

negative

Question 41

The first and rate-limiting enzyme in the cholesterol synthesis pathway is ____.

Answer 41

HMGCoA reductase (3-hydroxy-3-methylglutaryl coenzyme A reductase).

Question 42

Both cholesterol uptake and synthesis are regulated by the ____.

Answer 42

sterol regulatory element binding protein (SREBP)

Question 43

____, used to lower cholesterol, block the first (rate-limiting) step of cholesterol synthesis.

Answer 43

Statins

Question 44

Statins work on which step of cholesterol synthesis?

Answer 44

the first step- blocks HMGCoA reductase

Question 45

Both cholesterol ___ and ____ are regulated by the sterol regulatory element binding protein (SREBP)

Answer 45

uptake; synthesis

Question 46

____ is a protein containing a transcription factor that regulates both LDLR and all 30 of the synthesis proteins.

Answer 46

SREBP

Question 47

SREBP is a protein containing a transcription factor that regulates both ___ and ____.

Answer 47

LDLR; all 30 of the synthesis proteins

Question 48

If cholesterol is ___, the SREBP transcription factor is | released, moves to the nucleus, and activates all these genes.

Answer 48

low

Question 49

If cholesterol is low, the _____ is released, moves to the nucleus, and activates all these genes.

Answer 49

SREBP transcription factor

Question 50

The cholesterol level sensor is in the ____, where cholesterol is lowest in the cell and changes would be easiest to detect

Answer 50

ER membrane

Question 51

The cholesterol level sensor is in the ER membrane, where _____.

Answer 51

cholesterol is lowest in the cell and changes would be easiest to detect

Question 52

The proteases that cleave SREBP to release the bHLH are located in ____.

Answer 52

the Golgi complex

Question 53

SREBP must be held in ___ until cholesterol is low; then SREBP must move to ___ where it gets cleaved and the bHLH released.

Answer 53

the ER; the Golgi

Question 54

SCAP stands for?

Answer 54

SREBP cleavage activating protein

Question 55

____ binds both SREBP and sterols like cholesterol.

Answer 55

SCAP

Question 56

SCAP binds both ____ and _____.

Answer 56

SREBP; sterols like cholesterol

Question 57

Insig binds SCAP when _____ is high.

Answer 57

cholesterol

Question 58

Insig binds ____ when cholesterol is high.

Answer 58

SCAP

Question 59

____ binds SCAP when cholesterol is high.

Answer 59

Insig

Question 60

____, _____, and ____ are in complex when cholesterol is at normal levels.

Answer 60

SREBP, SCAP, Insig

Question 61

Insig binds SCAP only when cholesterol is ___.

Answer 61

high

Question 62

___ binds SCAP only when cholesterol is high.

Answer 62

Insig

Question 63

Insig binds ____ only when cholesterol is high.

Answer 63

SCAP

Question 64

When Insig binds SCAP, it blocks the ____.

Answer 64

SCAP signaling area.

Question 65

As cholesterol concentration drops, ___ no longer binds | ____ and the complex gets packaged into vesicles to go to the ____.

Answer 65

Insig; SCAP; Golgi

Question 66

As cholesterol concentration ____, Insig no longer binds | SCAP and the _____ gets packaged into vesicles to go to the Golgi.

Answer 66

dropsSCAP/SREBP complex

Question 67

One cleavage that releases bHLH cuts SREBP in the ____.

Answer 67

transmembrane domain

Question 68

One cleavage that releases ___ cuts ____ in the transmembrane domain.

Answer 68

bHLH; SREBP

Question 69

The cleavage of bHLH from SREBP within the membrane is known as _____.

Answer 69

RIP, regulated intramembrane proteolysis.

Question 70

___ 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.

Answer 70

RIP

Question 71

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 ____.

Answer 71

Notch signaling; Alzheimer’s disease

Question 72

When LDL cholesterol levels are less than 100 mg/dl (total plasma cholesterol of 170 mg/dl), heart attacks are ____.

Answer 72

rare

Question 73

When ____ cholesterol levels are less than ___ mg/dl (total plasma cholesterol of 170 mg/dl), heart attacks are rare.

Answer 73

LDL; 100

Question 74

Of the roughly 22,000 genes in the human genome, about ____ encode membrane transport proteins and ion channels.

Answer 74

one-tenth (2200)

Question 75

Of the roughly 22,000 genes in the human genome, about one-tenth (2200) encode ____.

Answer 75

membrane transport proteins and ion channels

Question 76

A variety of proteins are anchored to the membrane by ____.

Answer 76

glycosylphosphatidylinositol

Question 77

Glycosylphosphatidylinositol's function?

Answer 77

anchors proteins to the membrane

Question 78

____ is found only on the exoplasmic/extracellular face.

Answer 78

Glycosylphosphatidylinositol

Question 79

Glycosylphosphatidylinositol is found only on the ____.

Answer 79

exoplasmic/extracellular face