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Biochem 2 > Plasma membrane > Flashcards

Plasma membrane Flashcards

1
Q

3 main classes of membrane lipids

A
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2
Q

Are lipids polymers?

A

Ni

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3
Q

Lipids form membrane through ____ interactions

A

non-covalent

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4
Q

When a suspension of phospholipids is mechanically dispersed
in an aqueous solution,
the phospholipids aggregate into one of three structure
-> They are ___

A

1/ micelles
2/ Liposomes
3/ phospholipid bilayers

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5
Q

What is this?

A

Micelle

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6
Q

5 examples of Complex (hydrolyzable) lipids:

A
  1. triglycerides
  2. glycerophospholipids
  3. sphingolipids
  4. glycolipids (glycosphingolipids)
  5. plasmalogenes
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7
Q

Identify

A

Glycerophospholipids (general structure)

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8
Q

3 important examples of glycerophospholipids

A
  1. Phosphatidylcholine
  2. Phosphatidylserine
  3. Phosphotidulinositol 4-5-biphosphate
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9
Q

Identify this molecule

A

phosphatidylcholines

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10
Q

Products of this reaction

A
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11
Q

What happen to Phosphatidylserine when Ca2+ level elevates?

A

phosphatidylserine (PS) is externalized to the outer surface of the plasma membrane

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12
Q

Enzymes involving in Maintaining the membrane asymmetry of lipids?

A
  1. Flippases
  2. Scramblases
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13
Q

What is the role of Flippases?

A

move phospholipids (aminophospholipids) (e.g. phosphatidylserine) inwards, from the outer leaflet to the cytoplasmic leaflet of membranes.

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14
Q

Is flippase a transporter? If yes, is it required by ATP?

A

Yes, it is ATP-dependent

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15
Q

The role of Floppases?

A

Move choline-containing phospholipids to the outer leaflet

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16
Q

Do floppases require ATP?

A

YES!!!

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17
Q

What is the role of Scramblases?

A

equilibrate lipids across the bilayer

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18
Q

Do scramblases require ATP?

A

NO

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19
Q

Are all scramblases activated by calcium?

A

Some of them are activated by calcium.

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20
Q

When platelets are activated, what happen to the intracellular Ca2+ concentration?

A

It increases

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21
Q

When platelets are activated, the intracellular Ca2+ concentration increases.
-> This local Ca2+ increase inactivate (1)____ and activate (2)____.

A

1/ flippases
2/ scramblases

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22
Q

Name the 2 main enzymes involve in Breaking up phospholipid membranes

A
  1. (Pancreatic) phospholipase A2
  2. phospholipase C
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23
Q

What is the reaction catalyzed by (Pancreatic) phospholipase A2?

A
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24
Q

Structure of phosphatidylinositol bisphosphate (PIP2), showing sites of ____

A

cleavage

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25
Q

Structure of phosphatidylinositol bisphosphate (PIP2), showing sites of cleavage by ___

A

different phospholipases

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26
Q

Structure of phosphatidylinositol bisphosphate (PIP2), showing sites of cleavage
-> to produce ___ and ____

A

active mediators and summary diagram of the inflammatory mediators derived from phospholipids

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27
Q

What is the inhibitor of Phospholipase A2 activation?

A

Glucocorticoids

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28
Q

What is the role of TXA2

A

Thrombotic
Vasoconstrictor

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29
Q

What is the inhibitor of Cyclo-oxygenase?

A

NSAIDs
Glucocorticoids inhibit induction

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30
Q

What is the inhibitor of Phospholipase A2 activation?

A

Glucocorticoids

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31
Q

What is the inhibitor(s) of the process of making TXA2 from Cyclic endoperoxides?

A

TXA2 synthase inhibitors

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32
Q

What is the inhibitor of TXA2?

A

TXA2 anatagonists

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33
Q

What is the inhibitor of this process?

A

Leukotriene receptor for antagonists (e.g, zafirukast, montelukast)

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34
Q

What is the inhibitor(s) of these molecules?

A

PG antagonists

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35
Q

What is the role of TXA2

A

Thrombotic
Vasoconstrictor

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36
Q

What is the role of PGI2

A

Vasodilator
Hyperalgesic
Stops Platelet aggregation

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37
Q

How does the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) occur?

A
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38
Q

The hydrolysis of PI(4,5)P2 by PLC
-> What is the role of diacylglycerol after this?

A

Activates protein kinase C

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39
Q

The hydrolysis of PI(4,5)P2 by PLC
-> What is the role of IP3 after this?

A

Releases Ca2+ from the endoplasmic reticulum

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40
Q

How does The phosphorylation of PI(4,5)P2 occur?

A

insulin, growth factor or cytokines bind to adaptor
-> PI3K activates
-> phosphorylation of phosphatidylinositol 4,5-bisphosphate occur

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41
Q

The structure of Sphingolipids

A

The sphingolipids contain sphingosine, a longchain aliphatic amino alcohol, but no glycerol.

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42
Q

3 important types of Sphingolipids

A
  1. Sphingomyelin (phosphoric acid and choline.)
  2. Neutral glycolipids (glucosylcerebroside)
  3. Ganglioside GM2
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43
Q

Sphingolipids
-> Name of X if this sphingolipid is Neutral glycolipids (glucosylcerebroside)

A

Glucose

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44
Q

Sphingolipids
-> Neutral glycolipids (glucosylcerebroside)
-> Name 3 other classes of sphingolipids

A

erebrosides, globosides, and
gangliosides,
which contain sugar components.

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45
Q

Sphingolipids
-> Name of X if this sphingolipid is ganglioside GM2

A

Complex oligosaccharide

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46
Q

Enzyme deficiency of Hexosamindase
(name of the disease)

A

Tay-Sachs disease
(enzyme deficiency of …)

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47
Q

Enzyme deficiency of alpha-galactosidase
(name of the disease)

A

Fabry’s disease
(enzyme deficiency of …)

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48
Q

Enzyme deficiency of Arylsulfatase A
(name of the disease)

A

Metachromatic leukodystrophy
(enzyme deficiency of …)

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49
Q

Enzyme deficiency of Hexosamindase
(name of the disease)

A

Tay-Sachs disease
(enzyme deficiency of …)

50
Q

Enzyme deficiency of beta-galactosidase
(name of the disease)

A

Krabbe’s disease
(enzyme deficiency of …)

51
Q

Enzyme deficiency of beta-glucosidase
(name of the disease)

A

Gaucher’s disease
(enzyme deficiency of …)

52
Q

Enzyme deficiency of sphingomyelinase
(name of the disease)

A

Niemann-Pick disease disease
(enzyme deficiency of …)

53
Q

What does lipid raft contain?

A

It is enriched in sphingolipids, cholesterol

54
Q

Which pathway is affected by Hypercholesterolemia?

A

LDL receptor pathway

55
Q

The role of Cholesterol

A

changes membrane fluidity-

56
Q

Cholesterol has a direct inhibitory effect on ___ in the ER

A

HMG-CoA reductase

57
Q

What is Regulatory role of cholesterol, oxysterol?

58
Q

Describe The fluid mosaic model of membrane structure

A
  • The membrane consists of bimolecular lipid layer with proteins inserted init or bound to either surface
  • These proteins are integral protein, transmembrane protein and peripheral proteins
59
Q

What are integral proteins?

A

Proteins that are firmly embedded in the lipid layers

60
Q

What are transmembrane proteins?

A

Proteins that completely span the bilayer

61
Q

What are peripheral proteins?

A

Proteins that are loosely bound to the outer and inner surface of the membrane

62
Q

Identify this molecule

A

N-acetylneuraminic acid

63
Q

What are proteoglycans?

A

core protein+ glucoseaminoglycans

64
Q

What are glycoproteins?

A

protein+ oligosaccharides

65
Q

Composition of the ABO antigens?

A

The ABO Antigens Are Glycosphingolipids & Glycoproteins present in most cells of the body and in certain secretions

66
Q

For red blood cells, the membrane oligosaccharides that determine the antigenic natures of the ABO substances appear to be mostly present in (1)____, whereas in secretions the same oligosaccharides are present in (2)____

A
  1. glycosphingolipids
  2. glycoproteins
67
Q

the blood group substances are biantennary
-> Why?

A

they have two arms, formed at a branch point (not indicated) between the GlcNAc—R, and only one arm of the branch is shown.

68
Q

This is a Diagrammatic representation of the structures of the H, A, and B blood group substances
-> Explain

A
  1. R represents a long complex oligosaccharide chain, joined either to ceramide where the substances are glycosphingolipids, or to the polypeptide backbone of a protein via a serine or threonine residue where the substances are glycoproteins. Note that the blood group substances are biantennary; ie, they have two arms, formed at a branch point (not indicated) between the GlcNAc—R, and only one arm of the branch is shown.

Thus, the H, A, and B substances each contain two of their respective short oligosaccharide chains shown above.

The AB substance contains one type A chain and one type B chain.

69
Q

Glycophorin are rich in negatively charged ____ acids

70
Q

Glycophorin molecules account for approximately 60% of ____

A

the RBC’s negative surface charge

71
Q

What is the role of Glycophorin

A
  1. Modulating RBC-RBC interactions
  2. RBC interactions with the vascular endothelium and other circulating blood cells.
72
Q

What can decrease in erythrocyte glycophorin sialic acid content lead to?

A

increased erythrocyte aggregation

73
Q

______ situated at the ends of the oligosaccharide chains of many (plasma) glycoproteins

A

The residues of sialic acid (n-acetylneuraminic acid, NANA, Neu5Ac )

74
Q

Removal of the sialic acid residues by _____ (which enzyme?)

A

the enzyme sialidase (also called neuraminidase)

75
Q

Why does removal of the sialic acid residues by the enzyme sialidase (also called neuraminidase) occur?

A

It is a one way in which the body marks “old” proteins for destruction and replacement.

76
Q

The plasma membrane of hepatocytes contains _____

A

lectin molecules

77
Q

The role of asialoglycoprotein receptors

A

Receptor- asialoglycoprotein interaction triggers endocytosis and destruction of the asialoglycoprotein.

78
Q

Where can we find asialotransferrin?

A

It is found in CSF (cerebrospinal fluid), but not in normal serum or secretion fluids.

79
Q

What can the detection of asialotransferrin from nose or ear suggest?

A

It suggests the possibility of CSF leakage, e.g. in patients with skull injuries.

80
Q

What is the ratio of protein to lipid in human erythrocyte’s membrane?

81
Q

What is the ratio of protein to lipid in myelin’s membrane?

82
Q

What is the ratio of protein to lipid in mitochondrial inner membrane?

83
Q

Does LDL - LDL-receptor depend on pH?

84
Q

What happen On prolonged agonist activation of the G protein–coupled receptors (GPCR)?

A

selective GPCR kinases (GRKs) are recruited to the plasma membrane and phosphorylate the receptor

ARR: Arrestin,
Dyn: Dynamin GTPase→energy consuming process

85
Q

Types of transported structures included in facilitated diffusion?

A

Transporter
Channel

86
Q

Types of transported structures included in primary active transport

A
  1. ATPase
  2. pump
  3. ABC transporter
87
Q

Types of transported structures included in secondary active transport

A

transporter

88
Q

Hydrophobic molecules
Small uncharged polar molecules
Large uncharged polar molecules
Ions
=> Ranking the permeabilities of these substances from high to low

A
  1. Hydrophobic molecules
  2. Small uncharged polar molecules
  3. Large uncharged polar molecules
  4. Ions
89
Q

Are aquaporins permeable to protons?

90
Q

Why are aquaporins impermeable to H+?

A

they prevent proton hopping by water dipole reorientation

91
Q

What are the consequences of aquaporin channel mutation?

A

1/ Kidney – poliuria, polidipsia→diabetes insipidus
2/ Lens - cataract

92
Q

Composition of Aquagliceroporins

A
  1. Glycerol (adipocite, liver)
  2. Urea (liver)
  3. transport
93
Q

Glucose transporters in Humans
- GLUT1
-> Tissue(s) where expressed?

A
  1. Erythrocytes
  2. Blood-brain barrier
  3. Placenta
  4. Most tissues at a low level
94
Q

Glucose transporters in Humans
- GLUT1
-> What is the coding gene?

95
Q

Glucose transporters in Humans
- GLUT1
-> Role/ characteristics?

A
  1. Basal glucose uptake
  2. Defective in De Vivo disease
96
Q

Glucose transporters in Humans
- GLUT2
-> Tissue(s) where expressed?

A
  1. Liver
  2. Pancreatic islets
  3. Intestine
  4. Kidney
97
Q

Glucose transporters in Humans
- GLUT2
-> Role/characteristics?

A
  1. In liver and kidney
  2. Removal of excess glucose from blood
  3. In pancreas, regulation of insulin release
98
Q

Glucose transporters in Humans
- What is the coding gene of GLUT2?

99
Q

Glucose transporters in Humans
- GLUT3
-> Tissue(s) where expressed?

A
  1. Brain (neuron)
  2. Testis (sperm)
100
Q

Glucose transporters in Humans
- GLUT3
-> Role/characteristics?

A
  1. Basal glucose uptake
  2. High turnover number
101
Q

Glucose transporters in Humans
-> What is the coding gene of GLUT3?

102
Q

Glucose transporters in Humans
- GLUT4
-> Tissue(s) where expressed?

A

Muscle, fat, heart

103
Q

Glucose transporters in Humans
- GLUT4
-> Role/characteristics

A

Activity increased by insulin

104
Q

Glucose transporters in Humans
What is the coding gene of GLUT4

105
Q

Glucose transporters in Humans
- GLUT5
-> Tissue(s) where expressed?

A
  1. Intestine (primarily)
  2. Testis
  3. Kidney
106
Q

Glucose transporters in Humans
- GLUT5
-> Role/characteristics?

A

Primarily fructose transport

107
Q

What is the role of solute-carrier gene (SLC)?

A

solute-carrier gene (SLC) superfamily encodes membrane-bound transporters

108
Q

Glucose transporters in Humans
-> What are the expressed tissue(s) of GLUT 9?

A

Liver, kidney, intestine, lung, placenta

109
Q

Glucose transporters in Humans
-> Role/characteristics of GLUT 9

A

Urate and glucose transporter in liver, kidney

110
Q

Comparison of theme concentrations of Na+, K+, Ca2+ outside and inside a mammalian cell?

111
Q

What are The four classes of ATP-powered transport proteins?

A

1/ P-class pumps
2/ V-class proton pumps
3/ F-class proton pumps
4/ ATP-binding cassette transporters

112
Q

The four classes of ATP-powered transport proteins
-> Where do P-class pumps present?

A
  1. Plasma membrane of higher eukaryotes (Na+/K+ pump)
  2. Apical plasma membrane of mammalian stomach (H+/K+ pump)
  3. Plasma membrane of all eukaryotic cells (Ca2+ pump)
  4. Sarcoplasmic reticulum membrane in muscle cells (Ca2+ pump)
113
Q

The four classes of ATP-powered transport proteins
-> Where do V-class protons pump present?

A

1/ Endosomal and lysosomal membranes in animal cells
2/ Synaptic vesicles

114
Q

The four classes of ATP-powered transport proteins
-> Where do F-class protons pump present?

A

Inner mitochondrial membrane

115
Q

The four classes of ATP-powered transport proteins
-> Which 7 molecules can you find on ATP -binding cassette transporters?

A

1/ ABCA1
2/ P-glycoprotein
3/ MRP1
4/ MRP2
5/ ABCG5/ABCG8
6/ CFTR

116
Q

ATP -binding cassette transporters
-> The role of ABCA1?

A

HDL metabolism, reverse cholesterol transport

117
Q

ATP -binding cassette transporters
-> The role of ABCB1 / P-glycoprotein / multidrug resistance protein 1 (MDR1)?

A

resistance to chemotherapy

118
Q

ATP -binding cassette transporters
-> The role of ABCC1 / MRP1?

A

multidrug resistance

119
Q

ATP -binding cassette transporters
-> The role of ABCC2 / MRP2?

A

conjugated bilirubin (Dubin-Johnson syndrome)

120
Q

ATP -binding cassette transporters
-> The role of ABCG5/ABCG8?

A

cholesterol (liver, intestine)

Biochem 2 (38 decks)

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