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M&R 1 Flashcards

1
Q

Name the 3 main types of lipid:

A

1) Phospholipids
2) Sphingolipids
3) Cholesterol

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2
Q

Where in a cell are phospholipids synthesised?

A

Endoplasmic Reticulum

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3
Q

Give an example of a phospholipid:

A

Phosphatidylcholine
Phosphatidylserine
Phosphatidylinositol etc

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4
Q

What are the 2 types of sphingolipids?

A

1) Sphingomyelin

2) Glycolipids

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5
Q

What name is given to the type of sphingolipid which has a sugar monomer head group?

A

Cerebroside

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6
Q

What name is given to the type of sphingolipid which has an oligosaccharide head group?

A

Ganglioside

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7
Q

How can cholesterol increase the integrity and decrease the fluidity of a membrane?

A

Its rigid planar conjugated ring closely associates with the nearest fatty acid chain of a phospholipid, reducing aliphatic tail mobility

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8
Q

How can cholesterol decrease the integrity and increase the fluidity of a membrane?

A

Its rigid planar conjugated ring intercalates between phospholipids, separating them, preventing crystallisation

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9
Q

Approximately what percentage of a membrane is cholesterol?

A

~45-50%

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10
Q

What are the 4 possible mobility modes of a phospholipid in a bilayer?

A

1) Lateral diffusion
2) Flip-flop
3) Rotation
4) Flexion

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11
Q

What mode of phospholipid mobility is rare, and why?

A

Flip-flop

Thermodynamically unfavourable

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12
Q

What is an integral membrane protein?

A

A membrane protein which has 1+ transmembrane domains, and interacts with both the hydrophobic and hydrophilic domains of the bilayer

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13
Q

What are the possible ways a membrane protein can interact with the hydrophobic region of the bilayer?

A
  • alpha-helix insertion from the cytoplasmic side

- fatty acid post translational modification

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14
Q

What is used to remove integral membrane proteins for the lipid bilayer?

A
  • Solvents

- Detergents

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15
Q

What is the average length (in amino acid residues) of a transmembrane domain?

A

~ 18-22 amino acids

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16
Q

What are peripheral membrane proteins?

A

Proteins associated with the hydrophilic domain of a bilayer

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17
Q

What forces bind a peripheral membrane protein to a bilayer?

A

Electrostatic forces
Hydrogen bonds
Disulphide bridges

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18
Q

What are the 3 types of mobility of an integral membrane protein?

A

1) Fast lateral diffusion
2) Fast axial rotation
3) Conformation changes

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19
Q

Name the transmembrane glycoproteins which anchor ribosomes onto the endoplasmic reticulum:

A

Ribophorins

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20
Q

What is the average length of the signal sequence of an integral membrane protein, and what particle recognises this?

A

~ 18-30 amino acids

SRP = Signal Recognition Particle

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21
Q

Via which complex does integral membrane protein synthesis occur through, to enter the ER?

A

Peptide Translocation Complex

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22
Q

What are the main properties of a stop transfer signal?

A
  • Highly hydrophobic

- 18-20 amino acids long

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23
Q

Which enzymes cleave signal sequences?

A

Signal peptidases

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24
Q

Why is membrane asymmetry of proteins so important?

A

Proteins must face the direction of the signal to complete its function.
Ex: A receptor for an extracellular messenger MUST face the ECM

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25
Q

How do unsaturated fatty acids affect membrane fluidity?

A

Unsaturated fatty acids have a double bond, creating a kink in their structure, which reduces packing and prevents crystallisation

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26
Q

What is a Band 3 anion exchanger?

A

Cl-/HCO3- exchanger on the plasma membrane

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27
Q

What is Glycophorin A, and on what cell type is it expressed?

A

It is an antibody

Erythrocyte membranes

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28
Q

What is the function of Ankyrin, and in what cell type it is expressed?

A

It attaches the spectrin-actin cytoskeleton to integral membrane proteins
Erythrocytes

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29
Q

Which proteins form the alpha2/beta2 heterotetramer meshwork of the erythrocyte cytoskeleton?

A
  • Spectrin

- Actin

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30
Q

What is the role of Band 4.1 in an erythrocyte?

A

Stabilises spectrin-actin interaction

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31
Q

What kind of interaction does Band 4.1 make with an erythrocyte membrane?

A

It is a peripheral membrane protein, so interacts with the interior hydrophilic domain of the bilayer

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32
Q

What kind of interaction does Ankyrin make with an erythrocyte membrane?

A

It is a peripheral membrane protein, so interacts with the interior hydrophilic domain of the bilayer

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33
Q

What kind of interaction does Glycophorin A make with an erythrocyte membrane?

A

It is an integral membrane protein, so interacts with both the hydrophilic and hydrophobic domains of the membrane bilayer.

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34
Q

What kind of interaction does Band 3 anion exchanger make with the erythrocyte membrane?

A

It is an integral membrane protein, so interacts with both the hydrophilic and hydrophobic domains of the membrane bilayer.

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35
Q

Name 2 peripheral erythrocyte membrane proteins which bind the spectrin-actin cytoskeleton to intergral membrane proteins:

A

1) Ankyrin

2) Band 4.1

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36
Q

To which integral membrane protein does Ankyrin bind to?

A

Band 3 anion exchanger

37
Q

To which integral membrane protein does Band 4.1 bind to?

A

Glycophorin A

38
Q

How does hereditary spherocytosis cause anaemia?

A
  • Mutation causes reduced expression of spectrin by ~ 40-50%
  • Deformed cytoskeleton causes cell to round up, and cannot change shape to pass through capillaries without lysing
  • Reduced number of circulating red blood cells
39
Q

What is the name of the condition in which expression of spectrin is reduced by ~ 40-50%?

A

Hereditary Spherocytosis

40
Q

How does hereditary elliptocytosis cause anaemia?

A
  • Mutation causes defective spectrin formation
  • Cannot form heterotetramer with Actin
  • Deformed cytoskeleton prevents cell from regaining its bi-concave shape after becoming elliptoid through capillaries
  • Trapped and lysed by spleen
  • Reduced number of circulating red blood cells
41
Q

What is the name of the condition which prevents the formation of the spectrin-actin heterotetramer?

A

Hereditary elliptocytosis

42
Q

Name 4 molecules which can freely diffuse across a biological membrane:

A 
O2
CO2
N2
H2O
Benzene
Ethanol
Urea
Glycerol
Fat-soluble vitamins (ADEK)
43
Q

Name 4 atoms/molecules which cannot freely diffuse across a biological membrane:

A 
Glucose
Sucrose
Na+
Ca2+
K+
Mg2+
H+
Cl-
HCO3-
44
Q

What does the rate of passive diffusion depend on?

A
  • Concentration gradient

- Permeability of the membrane

45
Q

What does the rate of facilitated diffusion depend on?

A
  • Number of transport proteins available

- Temperature

46
Q

Define active transport:

A

Transport against an unfavourable concentration and/or electrical gradient, using energy directly or indirectly from ATP hydrolysis

47
Q

What is the difference between primary and secondary active transport?

A

Primary active transport uses energy directly from ATP hydrolysis
Secondary active transport uses energy indirectly from ATP hydrolysis (uses mvt of 1 molecule to drive another)

48
Q

Name the 2 types of primary active transporters:

A

1) ATPase ion transporters

2) ATP-binding cassette transporters

49
Q

Name the 3 types of ATPase ion transporters:

A

1) P-type
2) F-type
3) V-type

50
Q

Generally, how does a P-type ATPase ion transporter function?

A
  • ATP hydrolysis causes phosphorylation of the transporter
  • Causes conformational change
  • Ion channel opens/closes
51
Q

Give an example of a P-type ATPase ion transporter:

A

Na+/K+ ATPase pump

52
Q

What are the subunits of the NA+/K+ ATPase pump, and what are their functions?

A

alpha subunit: contains the ligand- and nucleotide- binding sites
beta subunit: directs channel to the plasma membrane from the endoplasmic reticulum
gamma subunit: anchors the channel within the plasma membrane

53
Q

Name 4 molecules which can bind to the alpha subunit of the Na+/K+ ATPase pump:

A

Na+
K+
ATP
Ouabain

54
Q

What type of ATPase ion transporter sets up and maintains the pH gradient between the ICM and ECM?

A

V-type ATPase

ie H+-ATPase

55
Q

What is the role of a V-type ATPase?

A

Set up and maintain the pH gradient between the ICM and ECM

56
Q

What type of ATPase ion transporter uses the H+ gradient for ATP synthesis?

A

F-type (ATP synthase)

57
Q

What is the role of an F-type ATPase ion transporter?

A

Uses the H+ gradient to drive ATP synthesis

58
Q

Name an F-type ATPase ion transporter:

A

ATP synthase

59
Q

What type of ATPase ion transporter does Ouabain bind to?

A

P-type : Na+/K+ ATPase pump

60
Q

What is the pH of the exctracellular fluid?

61
Q

What is the pH of the cytosol?

62
Q

What is the pH within mitochondria?

63
Q

What is the pH within a lysosome?

64
Q

What is the pH within secretory vesicles?

65
Q

In which cell component does pH = 7.7?

A

Mitochondria

66
Q

What is the [Ca2+] of the extracellular fluid?

67
Q

What is the [Ca2+] of the cytosol?

A

~ 10-100 nm

68
Q

Name the 2 types of secondary active transporters:

A

1) Symporters

2) Antiporters

69
Q

What type of transporter is the Na+/Ca2+ exchanger?

A

Secondary active transporter (antiporter)

70
Q

What are the 4 types of stimuli which may open channel proteins?

A
  • Mechanical stretch
  • Extracellular messengers
  • Intracellular messengers
  • Membrane voltage
71
Q

Name the 3 ion proteins which are most important in regulating [Ca2+] inside a cell:

A

1) PMCA (Plasma Membrane Ca2+ ATPase)
2) SERCA (Sarco- and Endo-plasmic Reticulum Ca2+ ATPase)
3) NCX (Na+/Ca2+ Exchanger)

72
Q

Which Ca2+ channel(s) have high affinity but low capacity for Ca2+?

A
  • PMCA (Plasma Membrane Ca2+ ATPase)

- SERCA (Sarco- and Endo-plasmic Reticulum Ca2+ ATPase)

73
Q

Which Ca2+ channel(s) have low affinity but high capacity for Ca2+?

A

NCX (Na+/Ca2+ Exchanger)

74
Q

Which Ca2+ channel removes most of the Ca2+ from a cell after muscle contraction? Why?

A

NCX (Na+/Ca2+ Exchanger)

It has a much higher capacity for Ca2+ transport, compared to the other Ca2+ channels

75
Q

Why does the intracellular [Ca2+] increase during ischaemia?

A
  • Glycolysis stops due to lack of O2
  • ATP levels are depleted
  • Na+/K+ ATPase stops due to lack of ATP
  • Intracellular [Na+] increases
  • NCX reverses, extruding Na+ from the cell, but bringing Ca2+ into the cell, increasing the [Ca2+]i
76
Q

How does glucose enter the apical side of intestinal epithelial cells? What ion channel is this mechanism dependent on?

A

Na+-Glucose cotransporter

Dependent on Na+/K+ ATPase

77
Q

Name 4 types of acid extruders:

A
  • V-type H+-ATPase
  • Na+/H+ exchanger
  • Cl-/HCO3- exchanger
  • NA+/HCO3- cotransporter
78
Q

Name 2 types of base extruders:

A
  • Band 3 anion exchanger (Cl-/HCO3-)

- Na+/HCO3- cotransporter

79
Q

Which channel in the ascending limb of the loop of Henle is blocked via loop diuretics?

A

NKCC

Na+/K+/Cl2- Cotransporter

80
Q

What type of diuretic blocks the Na+/K+/Cl2 cotransporter in the ascending limb of the loop of Henle?

A

Loop diuretic

81
Q

In what part of the kidney does a Loop diuretic work?

A

Ascending limb of the loop of Henle

82
Q

What channel is blocked in the distal convoluted tubule of the kidney via Thiazide diuretics?

A

NCCT

Na+/Cl2- Co-transporter

83
Q

What type of diuretic blocks the Na+/Cl2- cotransporter in the distal convoluted tubule of the kidney?

A

Thiazide diuretic

84
Q

In what part of the kidney does a Thiazide diuretic work?

A

Distal convoluted tubule

85
Q

What channel is blocked in the Cortical Collecting Duct of the kidney via Amiloride?

A

ENaC

Epithelial Na+ Channels

86
Q

What type of diuretic blocks the Epithelial Na+ Channels in the cortical collecting ducts of the kidney?

87
Q

In what part of the kidney does Amiloride work?

A

Cortical collecting duct

88
Q

Name 3 types of diuretics:

A

Loop diuretics
Spironolactane
Amiloride
Thiazine

89
Q

Which diuretic inhibits Aldosterone action at the kidney?

A

Spironolactone

ESA2 (27 decks)

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