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Molecular biology - Sarah > Biological Membranes and Membrane proteins > Flashcards

Biological Membranes and Membrane proteins Flashcards

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1
Q

Functions of cell membranes

A

Allow compartmentalization, act as barriers to diffusion, define organelles and the cell boundary, scaffolds for certain proteins, transport molecules, transmit information, Give shape, Assemble polysaccharides

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2
Q

osmoticum

A

A 2D liquid in which lipids and proteins float

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3
Q

Voltage inside of cell

A

20-80 mV (negative on the inside)

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4
Q

Lipids in the cell membrane

A

phsophoglycerides, sphingolipids, and sterols (cholesterol) (Fatty acids are 12-24 C in length)

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5
Q

Common phosphoglycerides

A

phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol

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6
Q

Components of phosphoglyceride

A

glycerol-3-phosphate, 2 fatty acyl chains, and polar head group (choline, serine, inositol, or ethanolamine)

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7
Q

The polar head group is ___ to the phosphate.

A

esterified

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8
Q

Plasmalogens

A

contain one fatty acyl chain attached to glycerol by an ester linkage and one attached by an ether linkage; these contain similar head groups as other phosphoglycerides

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9
Q

Phosphatidylinositol derivatives

A

DAG and IP3 (1,2-diacylglycerol and inositol 1,4,5-triphosphate after cleavage by activated phospholipase C These molecules are important secondary messengers/ important for signal transduction

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10
Q

Sphingolipids

A

derivatives of sphingosine, an amino alcohol with a long hydrocarbon chain. Fatty acyl chains connected by an amide bond.

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11
Q

Sphingomyelin

A

sphinolipid that contains phosphocholine head group

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12
Q

Glucosylcerebroside

A

sphingolipid with glucose as the head group

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13
Q

Animal, plant, and fungi sterols

A

animal - cholesterol fungi - ergosterol plant - sigmasterol

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14
Q

Stuff to know about cholesterol

A

4 ring hydrocarbon, polar hydroxyl group, non-polar hydrocarbon tail, rigid and planar steroid

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15
Q

Where is cholesterol synthesized?

A

on the endoplasmic reticulum (mostly in liver)

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16
Q

Atherosclerosis

A

results from cholesterol and other materials accumulating on the inner wall of arteries and limiting blood flow and oxygen delivery to tissues (accounts for 75% of cardiovascular deaths in the US)

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17
Q

Freezing point of membrane decreases with:

A

shorter chain length, decreased amount of sterol, increase in double bonds (increase fluidity or minimize amount of interaction between FA)

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18
Q

What proteins are on the intracellular face of the plasma membrane?

A

Phosphatidylserine, phosphatidylinositol, and phosphatidylethanolamine are found on the cytosolic face of the plasma membrane, cholesterol

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19
Q

What proteins are on the exoplasmic face?

A

Phosphatidylcholine and sphingomyelin, cholesterol

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20
Q

Three types of membrane proteins

A

Peripheral, lipid-anchored, and integral (or trans-membrane)

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21
Q

A component of integral proteins

A

alpha-helixes (20-25 hydrophobic amino acids)

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22
Q

Lipid-anchored proteins may be ____.

A

prenylated, GPI-anchored (Glycophosphatidylinositol), connected to a fatty acid

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23
Q

example of an integral membrane protein

A

glycophorin, bacteriorhodopsin, G-coupled protein receptors

24
Q

Examples of lipid-anchored proteins

A

Placental alkaline phosphatase is GPI-anchored, Ras and Rabs are Prenylated, V-src is acylated

25
Q

Detergents

A

natural or synthetic amphipathic molecules

26
Q

Components of lipid rafts

A

Depleted of glycolipids (phosphatidylethanolamine and phosphatidylcholine), enriched for glycosphingolipids and cholesterol (1:1:1 phospholipid:sphingolipid:cholesterol) Phospholipids are enriched for saturated fatty acids, specific peripheral and integral proteins (acylated but not prenylated)

27
Q

Proposed functions of Lipid rafts

A

Signaling platforms, Exocytosis, Endocytosis, Pathogen entry, apoptosis, cytoskeletal organization

28
Q

Evidence of membrane fluidity

A

Cell fusion experiments, FRAP (fluorescence recovery after photobleaching), Patching, and Laser tweezers

29
Q

FRAP

A

In this technique, the GFP signal is bleached by a short burst of strong laser light focused on the region of interest (ROI). This rapidly bleaches the molecules irreversibly, so they are not detected again. Restoration of fluorescence into the region represents unbleached molecules that have moved into the ROI

30
Q

Membrane skeleton

A

A non-covalent, submembranous array of proteins

31
Q

Function of membrane skeleton

A

Maintains cell shape, stabilizes the lipid bilayer, Creates and stabilizes domains of integral membrane proteins, regulates exocytosis and membrane vesicle trafficking and provides sites of attachment for the cytoskeleton

32
Q

Major glycoproteins in the membrane skeleton

A

alpha spectrin, beta spectrin, and Band 3 (in order of least to greatest molecular weight)

33
Q

Band 3 protein

A

20-25% of total protein, HCO3/Cl antiporter, 30% is immobile by FRAP, Can be cross-linked to ankyrin, major integral membrane protein

34
Q

Glycophorin

A

integral membrane protein, interacts with Band 4.1

35
Q

Peripheral cytosolic proteins in the cell membrane

A

alpha spectrin, beta spectrin, glycophorin, actin…and band 4.1?

36
Q

Actin interacts with ___

A

spectrin

37
Q

Band 4.1 is an anchor for ___

A

spectrin

38
Q

Spectrin heterodimers

A

Associates beta spectrin subunit (N-terminus) with actin (F-actin or actin filaments) Modulated by cell adhesion molecule, phosphorylation, and phosphatidylinositol 4,5-bisphosphate Binds to ankyrin and Band 4.1 2 anti-parallel strands

39
Q

Hereditary Spherocytosis

A

small, spherical RBC with increased fragility, decreased flexibility usually ankyrin mutation, but can be alpha or beta spectrin mutation, protein 4.2 or Band 3 protein mutation

40
Q

Things that can pass through the membrane

A

carbon dioxide, nitrogen, oxygen, ethanol water and urea somewhat permeable

41
Q

Things that can’t pass through the membrane

A

glucose, fructose, ions, amino acids, ATP, Glucose-6-phosphate, proteins, nucleic acids

42
Q

Transport/integral membrane protein types

A

transporters, channels, pumps

43
Q

Sodium potassium pumps

A

ATP powered, 3 Sodium out (Na we don’t want that), 2 potassium in (k, it’s good, let’s get that shit in here) Ouabain and digoxin disable sodium potassium pump

44
Q

Things that inhibit the sodium potassium pump

A

ouabin and digoxin

45
Q

Ion channels

A

facilitated diffusion, without ATP, molecule follows concentration gradient Aquaporins, stretch-activated ion channels

46
Q

Symporter

A

two molecules moving in the same direction, one moved up concentration gradient, other down

47
Q

Antiporter

A

Two molecules moving in different directions, one moving up concentration gradient and the other down

48
Q

Example of a uniporter

A

GLUT1, moves glucose down it’s concentration gradient (in erythrocytes)

49
Q

ABCPs

A

ATP-binding cassette proteins - superfamily of pumps with important biological function

50
Q

Defects in CFTR cause ____.

A

cystic fibrosis (It transports chloride ions)

51
Q

ABCB1

A

(or MDR1), expressed in adrenal, kidney, and brain, exports lipophilic drugs (ATP-binding cassette protein 1)

52
Q

ABCB4

A

(ATP-binding casette protein 4) (MDR2), expressed in Liver, exports phosphatidylcholine into bile

53
Q

CFTR

A

defect causes cystic fibrosis, expressed in exocrine tissue, transports chloride ions

54
Q

What does Digoxin do?

A

It inhibits the sodium potassium pump. This increases sodium concentrations inside the cell. There is a calcium/potassium antiporter That transports sodium in down it’s concentration gradient (the one created by sodium potassium) and transports calcium out of the cell against it’s concentration gradient. In effect, digoxin increases calcium concentration inside the cell by decreasing the concentration gradient of sodium. This helps the heart beat with a stronger, more regular rhythm.

55
Q
A

A) Actin

B) Adducin

C) Tropomyosin

D) Band 4.1

E) Ankyrin

F) Spectrin dimer

G) Glycophorin

Molecular biology - Sarah (6 decks)

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