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My ESA 2 > M&R > Flashcards

M&R Flashcards

1
Q

What is the only phospholipid not based on glycerol?

A

Sphingomyelin

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2
Q

List 5 general functions of biological membranes

A
  1. Continuous highly selective permeability barrier
  2. Allows control of the enclosed chemical environment
  3. Recognition - signalling molecules, adhesion proteins, immune surveillance
  4. Communication - control the flow of information between cells and their environment
  5. Signal generation in response to stimuli (chemical, electrical)
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3
Q

What significance does CIs double bonds in fatty acid chains on phospholipids have?

A

Introduce a kink in the chain, reducing phospholipid packing

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4
Q

What are glycolipids?

A

Sugar containing lipids

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5
Q

Given2 types of glycolipids

A

Cerebrosides - head group sugar monomers

Gangliosides - head group oligsosaccharides (sugar multimers)

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6
Q

What % respectively is a membrane constituted of lipid, protein and carbohydrate?

A

40% lipid
60% protein
1-10% carbohydrate
(20% of total weight is H2O)

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7
Q

What % of the total membrane lipid is cholesterol?

A

45%

Distribution of other lipids is related to function and tissue specific

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8
Q

List the 4 permitted modes of mobility for lipid molecules in the lipid bilayer

A
  1. Intra-chain motion - kink formation in the fatty acyl chains
  2. Axial rotation (fast)
  3. Lateral diffusion wishing plane of bilayer (fast)
  4. Flip-flop - movement of lipid molecules from one half of the bilayer to the other half on a one for one exchange basis.
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9
Q

How can peripheral membrane proteins be removed?

A

Changes to pH or ionic strength

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10
Q

How are integral membrane proteins removed?

A

Use of agents (detergents, solvents) that compete for non-polar interactions in the bilayer

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11
Q

List the modes of motion permitted for proteins in bilayers

A
  1. Conformational change
  2. Rotational
  3. Lateral

No flip flop!

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12
Q

List 4 mechanisms of restriction of membrane protein mobility

A
  1. Aggregates
  2. Tethering
  3. Interactions with other cells
  4. Lipid mediated effects - proteins tend to separate out into the fluid phase or cholesterol poor regions.
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13
Q

What are hydropathy plots used for?

A

For determining how many transmembrane regions a protein has

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14
Q

What proteins is the erythrocyte cytoskeleton composed of?

A

Spectrin and actin
(actin-spectrin network, attached to the membrane by adapted proteins ankyrin and glycophorin, maintaining shape of RBCs)

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15
Q

What causes symptoms in hereditary Spherocytosis?

A

Spectrin is depleted by 40-50%

Erythrocytes ‘round up’, so increased cell lysis, decreased RBC lifespan

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16
Q

What causes symptoms in hereditary Elliptocytosis?

A

Spectrum molecules are unable to form heterotramers (fragile elliptoid cells)

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17
Q

Give 6 roles of transport processes

A
  1. Maintenance of ionic composition
  2. Maintenance of intracellular pH
  3. Concentration of metabolic fuels and building blocks
  4. Regulation of cell volume
  5. The extrusion of waste products of metabolism and toxic substances
  6. The generation of ion gradients necessary for the electrical excitability of nerve and muscle
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18
Q

Give 3 mechanisms for regulating protein transporters

A

Ligand gated - respond to ligand binding to receptor site
Voltage gated - respond gets in potential difference across membrane
Gap junction - close when cellular Ca2+ rises above 10uM, or cell becomes acidic

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19
Q

Name 2 things which influence is movement is active or passive

A

Concentration gradient

Membrane potential

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20
Q

What is the free ion distribution across the cell membrane for Na+?

A

145mM Extracellular

12mM Intracellular

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21
Q

What is the free ion distribution across the cell membrane for K+?

A

Extracellular 4mM

Intracellular 155mM

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22
Q

What is the free ion distribution across the cell membrane for Cl-?

A

Extracellular 123mM

Intracellular 4.2mM

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23
Q

What is the free ion distribution across the cell membrane for Ca2+?

A

Extracellular 1.5mM

Intracellular 10^-7 M (0.0001mM)

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24
Q

What does a uniport transport?

A

Transports a single molecule in a single direction

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25
Q

What does a symport transport?

A

Transports 2 molecules in the SAME direction

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26
Q

What does and anti port transport?

A

Transports 1 molecule in and 1 molecule out in a single cycle

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27
Q

Name 4 Ca2+ transporters

A

NCX (Na+ / Ca2+ exchanger)
SERCA (sarco(endo)plasmic reticulum Ca2+ - ATPase)
PMCA (plasma membrane Ca2+ - ATPase)
Ca2+ uniporters (mitochondria)

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28
Q

Name 2 calcium transporters with high affinity, low capacity

A

PMCA

SERCA

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29
Q

Name a calcium transporter which works via secondary active transport

A

NCX

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30
Q

What does sodium calcium exchanger (NCX) exchange?

A

3Na+ in for 1 Ca2+ out

Therefore is electrogenic, membrane potential dependent, can reverse in depolarised cells

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31
Q

Name 2 acid extruders

A

NHE (Na+/H+ exchanger)

NBC (sodium bicarbonate cotransporter. Na+ dependent Cl-/HCO3- exchanger)

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32
Q

Name a base extruder

A

AE - acidifies cell
Cl-/HCO3- exchanger (anion exchanger)

NBC - alkalinises cell
Na+-bicarbonate-chloride cotransporter

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33
Q

How do you measure a membrane potential?

A

Use a microelectrode (fine glass pipette, tip diameter

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34
Q

Are membrane potentials expressed inside to outside, or outside to inside?

A

Inside the cell relative to extracellular solution

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35
Q

What is the unit of measurement for membrane potentials?

A

Millivolts mV

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36
Q

What dominates the membrane ionic potential in most cells?

A

K+ channels

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37
Q

In the Nernst equation, what does z stand for?

A

X stands for the valency (charge) of the ion moving

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38
Q

What is depolarization?

A

Decrease in negativity
Cell interior becomes less negative
E.g. -70mV to -50mV

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39
Q

What is hyperpolarization?

A

Increase in negativity
Cell interior becomes more negative
E.g. Change from -70mV to -90mV

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40
Q

Given3 types of gating for channels

A
  1. Ligand gating - respond to binding of chemical ligand
  2. Voltage gating - respond to changes in membrane potential
  3. Mechanical gating - respond to membrane deformation e.g. In mechanoreceptors
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41
Q

What makes fast synaptic transmission?

A

Receptor is also a ligand-gated ion channel (binding & channel event are linked directly)

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42
Q

What do inhibitory synapses cause?

A

Hyperpolarization

Further from resting membrane potential/threshold

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43
Q

What makes slow synaptic transmission?

A

The receptor and channel are separate proteins

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44
Q

Name the 2 basic patterns for the separate proteins of slow synaptic transmission mechanisms

A
  1. Direct G-protein gating

2. Gating via an intracellular messenger

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45
Q

Name 2 factors other than ion channels which can influence membrane potential

A
  1. Changes in ion concentration

2. Electrogenic pumps (I.e. Na+/K+ - ATPase)

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46
Q

What is an action potential?

A

Change in voltage across membrane
Depends on ionic gradients & relative permeability of the membrane
Only occurs if a threshold level is reached - all or nothing
Propagated without loss of amplitude

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47
Q

By how much is the intracellular Na+ conc. Increases by during each action potential?

A

(Only) 40uM.

~0.4% increase

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48
Q

Name 3 ways of investigating the mechanism of action potential generation

A
  1. Voltage-clamping (controls the membrane potential so that the ionic currents can be measured)
  2. Using different ionic concentrations (the contribution of various ions can be assessed)
  3. Patch-clamping (enables currents flowing through individual ion channels to be measured)
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49
Q

Depolarization to threshold initiates an action potential where in the neurone?

A

Axon hillock

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50
Q

What is the ARP?

A

Absolute Refractory Period:

Nearly all Na+ channels are in the inactivated state

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51
Q

What is the RRP?

A

Relative Refractory Period:
Na+ channels are recovering from inactivation, the excitability returns towards normal as the number of channels in the inactivated state decreases

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52
Q

What is accommondation?

A

The longer the time taken for stimulus to reach threshold value, the larger the threshold value necessary to initiate an AP, and less positive (smaller) the peak. (More Na+ channels switched to inactive state)

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53
Q

Describe the structure of a Na+ channel

A

1 polypeptide chain, consists of 4 repeats.
Inactivating particle between repeat 3&4, which can plug pore.
Each repeat consists of 6 transmembrane domains.
No. 4 contains many +ve AAs, so causes conformational change on depolarization making it more likely inactivating particle will block pore (putting channel in the inactive state). This is reversed on hyperpolarization.

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54
Q

Describe the structure of a K+ channel

A

Consist of 4 alpha subunits
Each subunit has 6 transmembrane domains
No. 4 contains many +ve AAs, so causes conformational change on depolarization

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55
Q

How do local anaesthetics, e.g. Procaine, work?

A

Act by blocking Na+ channels (acting like inactivating particles)

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56
Q

In what order do local anaesthetics block conduction in nerve fibres?

A

Small myelinated axons
Non-myelinated axons
Large myelinated axons

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57
Q

How is the conduction velocity of an axon measured?

A

Distance between stimulating electrode and recording electrode, as well as time gap between stimulus as AP being registered are measured. S=D/T

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58
Q

List 3 properties that lead to high conduction velocity in an axon

A
  1. High membrane resistance
  2. Low membrane capacitance
  3. Large axon diameter (therefore low cytoplasmic resistance)
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59
Q

What is capacitance?

A

The ability to store charge - a property of the lipid bilayer

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60
Q

What cells myelinated peripheral axons?

A

Schwann cells

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61
Q

What cells myelinated axons in the CNS?

A

Oligodendrocytes

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62
Q

What is the rate of peripheral nerve regeneration?

A

1-5mm/day

Faster in bigger neurones

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63
Q

Describe the sequence of events that results in release of neurotransmitter at a synapse

A 
Ca2+ entry via voltage-gated Ca2+ channels
Ca2+ binds to synaptotagmin 
Vessel brought close to membrane
Snare complex makes a fusion pore
Transmitter released via this pore
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64
Q

What does synaptotagmin do?

A

Brings vesicle towards synaptic membrane

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65
Q

What does the snare complex do?

A

Enables formation of a fusion pore

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66
Q

How many ACh molecules bind to a nicotinic receptor? And what does it cause?

A

2

Opens ligand gated channel, enables K+ efflux and Na+ influx

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67
Q

Describe the structure of a nicotinic receptor

A

5 subunits

2 alpha subunits to which ACh binds, causing confirmational change which causes receptor pore to open

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68
Q

How does curare work?

A

Blocks ACh binding site (competitive)

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69
Q

Name the 2 types of blockers for nicotinic ACh receptors and describe their mechanism of action.

A

Competitive - block ACh binding
Depolarizing - agonists at ACh receptor, cause depolarization, Na+ channels open and therefore become inactivated. Prolonged activation as drug not broken down by AChE so not reset, Na+ channels remain inactivated.

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70
Q

What are nACh receptors?

A

Nicotinic Acetylecholine receptors

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71
Q

Which ACh receptor produces a faster response and why?

A

nAChR - fast as it is a ligand gated ion channel

mAChR - relatively slow as they are coupled to G-proteins which trigger a cascade of events in the cell.

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72
Q

Give 2 advantages of having a large inward gradient of Ca2+

A
  1. Changes in [Ca2+]i occur rapidly with movement of little Ca2+
  2. Little Ca2+ has to be removed to re-establish resting conditions
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73
Q

Give 2 disadvantages of having a large inward Ca2+ gradient

A
  1. Energy expensive

2. Inability to deal with Ca2+ easily leads to Ca2+ overload, loss of regulation and cell death.

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74
Q

How is the Ca2+ gradient maintained?

A

Relative Impermeability of the plasma membrane
Ability to expel Ca2+ across the plasma membrane via Ca2+-ATPase / Na+-Ca2+ exchanger
Ca2+ buffers
Intracellular Ca2+ stores

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75
Q

What is the feedback mechanism controlling intracellular Ca2+ levels?

A

[Ca2+]i levels increase
Ca2+ binds to calmodulin
Ca2+-calmodulin complex binds to Ca2+-ATPase
Ca2+-ATPase removes Ca2+

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76
Q

Give two types of channels which enable Ca2+ influx across the plasma membrane

A 
Voltage-operated Ca2+ channels (VOCC)
Ionotropic receptors (ligand gated)
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77
Q

What are the mechanisms for altering intracellular Ca2+ levels?

A

Ca2+ influx across plasma membrane
Ca2+ release from rapidly releasable intracellular stores (sarcoendoplasmic reticulum)
Non-rapidly releasable stores (mitochondria)

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78
Q

How is Ca2+ release from the Sarcoplasmic reticulum mediated?

A

G-protein coupled receptors (GPCRs)

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79
Q

What type of ACh receptors utilise G-proteins?

A

Muscarinic

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80
Q

How many parts is a heterotrimeric G-protein comprised of, and what are they called?

A

3

Alpha, beta, gamma

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81
Q

What is the active part of a heterotrimeric G-protein once it has been split?

A

Alpha

Beta and gamma remain stuck together

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82
Q

What does alpha q do?

A

Activates phosopholipase C, which converts PIP2 (a plasma protein) to
IP3 (free activator molecule)
+
diacylglycerol (remains in plasma membrane)

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83
Q

What does IP3 do?

A

IP3 binds to IP3 receptor on sarcoendoplasmic reticulum, enabling Ca2+ efflux from it.

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84
Q

In calcium induced calcium release, where does the Ca2+ come from?

A

VOCCs
Inotropic receptors
Intracellular stores

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85
Q

What activates the ryanodine receptor and what does it enable?

A

Ca2+ in cytoplasm (or possibly cyclic ADP-ribose)

Enables more Ca2+ to leave Sarcoplasmic reticulum

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86
Q

How are IP3 receptors effected by CICR?

A

Easier for Ca2+ to leave sarcoendoplasmic reticulum at low intracellular Ca2+ levels, and vice versa

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87
Q

What percentage Ca2+ comes from intracellular stores and extracellular in the cardiac myocyte?

A

85% intracellular stores

15% extracellular

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88
Q

What happens to NCX during influx of Ca2+?

A

Initial depolorisation reverses NXC to cause Ca2+ influx. Once Ca2+ levels are raised enough it reverts back to normal direction (Na+ influx, Ca2+ efflux)

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89
Q

Describe the Ca2+ channels on mitochondria. What are they important for?

A 
Uniporter (Low affinity, high capacity)
Important for:
Ca2+ buffering
Stimulation of mitochondrial metabolism
Roll in cell death (apoptosis)
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90
Q

Why must Ca2+ levels be restored to basal state?

A

Too much Ca2+ for too long is toxic

Repetitive signalling requires restoration of basal state

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91
Q

How are Ca2+ levels restored to basal state?

A

Recycling of released (cytosolic) Ca2+

VOCC &/or capacitative Ca2+ entry

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92
Q

What is a ligand?

A

Any molecule that binds specifically to a receptor site

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93
Q

Define receptor

A

A molecule that recognises specifically a second molecule (ligand) or family of molecules & which in response to ligand binding brings about regulation of a cellular process. Silent at rest.

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94
Q

If ligand binding produces activation of a receptor, what is it termed?

A

Agonist

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95
Q

If ligand binding does not cause activation of a receptor (opposing the activation), what is it termed?

A

Antagonist

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96
Q

What is KD?

A

The contraction of substrate at which half of the receptor sites are filled of a particular receptor

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97
Q

What is KM?

A

The contraction of substrate at which half of the receptor sites are filled of a particular enzyme

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98
Q

Binding generally has higher affinity at receptor sites or enzyme active sites?

A

Higher affinity at receptor sites

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99
Q

How are receptors classified?

A

According to their signalling molecule (agonist) recognised, subclassified according to their affinity to a series of antagonists.

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100
Q

What’s are receptors and acceptors?

A

Receptor: Silent at rest, agonist binding stimulates a biological response.

Acceptor: Operate in absence of ligand. Ligand binding alone produces no response (modulated only).

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101
Q

Name 4 mechanisms of signal transduction

A
  1. Membrane-bound receptors with integral ion channels
  2. Membrane-bound receptors with integral enzyme activity
  3. Membrane-bound receptors which couple to effectors through transduction proteins
  4. Intracellular receptors
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102
Q

What is phagocytosis?

A

Internalisation of particulate matter

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103
Q

What is pinocytosis?

A

Invagination of the plasma membrane to form a vesicle. Permits uptake of extracellular solutes.

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104
Q

What is endocytosis?

A

The selective internalisation of molecules into the cell by binding to specific cell surface receptors

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105
Q

Give an example of receptor-mediated endocytosis

A

Cholesterol uptake

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106
Q

Describe the structure of LDLs

A

Core of sterilised cholesterol esters, covered by a phospholipid and cholesterol monolayer, containing apoprotein B.

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107
Q

How are clathrin coats assembled?

A

Triskelions spontaneously form clathrin coats

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108
Q

How is a clathrin coat disassembled?

A

Uncoated by an ATP-dependent uncoating protein

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109
Q

Describe the structure of triskelions

A

Coat structures made up of hexagons and pentagons

Comprise 3 clathrin heavy chains, and 3 light chains.

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110
Q

What is the CURL?

A

Compartment for the Uncoupling of Receptor and Ligand, also known as the endosome.

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111
Q

How is the low pH of the endosome maintained?

A

ATP-dependent proton pump

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112
Q

Describe the process of the receptor mediated endocytosis of LDLs

A

Receptors, located in coated pits, binds to LDL
Coated pit invaginate and pinch off from the plasma membrane to form coated vesicle
Coated vesicles are quickly uncoated
Uncoated vesicles then fuse with larger smooth vesicle CURL
At lower pH here LDL-receptor has low affinity for LDL particle, so dissassosiate
Transmembranous receptors are sequestered to a domain within CURL - buds off as a vesicle & recycled back to plasma membrane
CURL containing LDL fuse with lysosomes such that cholesterol can be hydrolysed from the esters and released into the cell

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113
Q

Name 3 possible mutations in LDL receptors that can lead to hypercholesterolaemia

A
  1. Receptor deficiency
  2. Non-functional receptor
  3. Receptor binding normal, but no internalisation due to deletion in the c-terminal of receptor that makes the interaction with the coated pits.
114
Q

How is the clathrin coat attached to the plasma membrane?

A

By a number of integral membrane adapted proteins which form associations with both the clathrin and receptors, locating receptors over the coated pit.

115
Q

Describe the process of endocytosis of Fe3+ (ferric ions) by transferrin

A

Ferrotransferrin (containing Fe3+) binds to transferrin receptor at coated pit
Coated vesicle buds off and is uncoated
Uncoated vesicle reaches CURL (acidic), Fe3+ ions are released
Apotransferrin remains bound to receptor at this pH
Complex sorted in the CURL for recycling back to plasma membrane
At neutral pH apotransferrin dissociates from transferrin receptor again

116
Q

Describe the 2 unique parts of endocytosis of insulin

A

Insulin receptors only congregate over the covered pits when agonist is bound (binding causes conformational change in receptor enabling it to be recognised by coated pit)
In CURL, insulin remains bound to receptor. Complex is targeted to lysosome for degradation (enables reduction in no. insulin receptors (down regulation) desensitising bell to continued presence of high circulation insulin concs.)

117
Q

Describe unique parts of endocytosis of immunoglobulin

A

Remains bound to receptor in CURL, together targeted for transfer vesicle, in turn for bile
Once in bile, immunoglobulin is released from receptor by proteolytic cleavage

118
Q

What is transcytosis? Give an example

A

When ligand remains bound to its receptor in CURL

E.g. Immunoglobulin - secreted with a bound ‘secretory component’ derived from the receptor

119
Q

Are coated pits unique for each type of receptor?

A

No - receptors for different ligands enter cell via same coated pit, pathway from such to endosome is common for all proteins, targeted to discreet regions of CURL once there.

120
Q

How do viruses take advantage of RME?

A

Enron cells via clathrin-coated pore.

Once transported to favourable in pH within CURL are activated, so undergo replication ect.

121
Q

What are the 3 ‘superfamilies’ of cell surface receptor?

A
  1. Ligand-gated (receptor operated) ion channels
  2. Receptors with intrinsic enzyme activity (receptor tyrosine kinases)
  3. G protein-coupled (7TM) receptors
122
Q

What does an agonist do?

A

Binds to receptor and activates it

123
Q

What does an antagonist do?

A

Binds to receptor without activating it (blocks effects of agonist)

124
Q

Describe the shared basic structure of all GPCRs

A

Single polypeptide chain (300-1200 amino acids)
7-transmembrane (7TM) spanning regions
Extracellular N-terminal
Intracellular C-terminal

125
Q

Describe the 2 regions of GPCRs that can be responsible for ligand binding

A

Ligand binding site formed by:
2-3 of the transmembrane domains
N-terminal region

126
Q

What does ‘G protein’ stand for?

A

Guanine-nucleotide binding protein

127
Q

How is G-protein signalling terminated?

A

Alpha or beta/gamma interaction with the effectors lasts only until the alpha subunits GTPase activity hydrolases GTP back to GDP. Alpha-GDP and beta/gamma subunits then reform an inactive heterotrimeric complex.

128
Q

How are G-proteins activated?

A

GPCR -GProtein interaction activates the G protein by causing GTP to exchange for GDP on the G-Protein alpha subunit. The alpha-beta/gamma complex immediately dissociates, and each part can then interact with effector proteins

129
Q

What does an agonist do?

A

Binds to receptor and activates it

130
Q

What does an antagonist do?

A

Binds to receptor without activating it (blocks effects of agonist)

131
Q

Describe the shared basic structure of all GPCRs

A

Single polypeptide chain (300-1200 amino acids)
7-transmembrane (7TM) spanning regions
Extracellular N-terminal
Intracellular C-terminal

132
Q

Describe the 2 regions of GPCRs that can be responsible for ligand binding

A

Ligand binding site formed by:
2-3 of the transmembrane domains
N-terminal region

133
Q

What does ‘G protein’ stand for?

A

Guanine-nucleotide binding protein

134
Q

How is G-protein signalling terminated?

A

Alpha or beta/gamma interaction with the effectors lasts only until the alpha subunits GTPase activity hydrolases GTP back to GDP. Alpha-GDP and beta/gamma subunits then reform an inactive heterotrimeric complex.

135
Q

How are G-proteins activated?

A

GPCR -GProtein interaction activates the G protein by causing GTP to exchange for GDP on the G-Protein alpha subunit

136
Q

How are G-proteins activated?

A

GPCR -GProtein interaction activates the G protein by causing GTP to exchange for GDP on the G-Protein alpha subunit

137
Q

Give 2 examples of possible effectors

A

Ion channels e.g. VOCCs

Enzymes e.g. Adenyl cyclase, phospholipase C, phosphoinostidide 3-kinase (PI3K), cGMP phosphodiesterase

138
Q

What type of membrane protein is Adenylyl Cyclase?

A

Integral

139
Q

How does activated adenylyl cyclase exert its effect with the cell?

A

Hydrolases cellular ATP to generate cyclic AMP, which interacts with a specific protein kinase (PKA), which in turn can phosphorylate a variety of other proteins within cell to effect their activities.

140
Q

What does activated adenylyl cyclase do?

A

Increases glycogenolysis/gluconeogenesis in the liver
Increases lipolysis in adipose tissue
Relaxation of a variety of types of smooth muscle
Positive inotropic and chronotropic effects in the heart

141
Q

What is PIP2 cleaved into?

A

Two second messengers, IP3 and DAG (diacylglycerol)

142
Q

What does Phosopholipase C do?

A

Catalyses the cleavage of the membrane phosopholipid PIP2 (into IP3 and DAG)

143
Q

What parts of the body does activated Phospholipase C effect?

A

Smooth muscle contraction of GI tract, airways/vasculature
Mast cell degranulation
Platelet aggregation

144
Q

Give the 3 key features of signal transduction in biological membranes

A
  1. Diversity
  2. Specificity
  3. Amplification
145
Q

What governs receptor activation?

A

Intrinsic efficacy

146
Q

What is the efficacy of a drug governed by?

A

Intrinsic efficacy PLUS other things that influence the response (cell/tissue dependent factors)

147
Q

What is intrinsic efficacy?

A

The ligands ability to produce n active receptor

148
Q

What is Kd?

A

Dissociation constant
A measure of drug-receptor affinity. The concentration of ligand required to occupy 50% of the available receptors.
(Lower value = Higher affinity)

149
Q

What is the EC50?

A

The Effective Concentration giving 50% of the maximal response

150
Q

What is efficacy a measure of?

A

Potency

Affinity + intrinsic efficacy + cell/tissue dependent events

151
Q

What is the IC50?

A

Inhibitory Concentration giving 50% of maximum inhibition

152
Q

How may selectivity in drugs be achieved?

A

Drugs may have selective affinity or selective efficacy

153
Q

What are ‘spare receptors’?

A

When a cell has more receptors than those which would need to be occupied to produce the maximal response. Spare receptors being activated will not amplify signal any more. Often in amplification/transduction systems. Increases sensitivity.

154
Q

Why is having spare receptors advantageous?

A

Increases sensitivity

155
Q

Name the 3 types of antagonist

A
  1. Reversible competitive antagonism
  2. Irreversible competitive antagonism
  3. Non-competitive antagonism (generally allosteric or even post-receptor)
156
Q

What is Kb?

A

Kd, except determined pharmacologically

157
Q

How could first pass metabolism be avoided?

A

Using a parenteral, sublingual or rectal route

158
Q

What are 4 questions you should always ask before prescribing drugs?

A
  1. Is drug getting into patient? (pharmaceutical process)
  2. Is drug getting to site of action? (pharmacokinetic process)
  3. Is drug producing desired effect? (Pharmacodynamic process)
  4. Is this translated to a therapeutic effect? (Therapeutic process)
159
Q

What are pharmacokinetics?

A

‘What the body does to a drug’

160
Q

What are pharmacodynamics?

A

‘What the drug does to a body’

161
Q

Name enteral sites of drug administration

A

Sublingual, oral, rectal

162
Q

Name parenteral sites of drug administration

A

Subcutaneous, intramuscular, intravenous, inhalation, transdermal

163
Q

Define the bioavailability of a drug

A

The proportion of drug given orally/any route other than IV, that reaches circulation unchanged.
Can be expressed as amount or rate

164
Q

What is the therapeutic ratio?

A

Maximum tolerated dose LD50
___________________________ _________
Minimum effective dose ED50

165
Q

What is the volume of distribution?

A

The theoretical volume into which drug is distributed, if this occurred instantaneously. Obtained by extrapolation of plasma levels to zero time.

166
Q

It’s the free drug which exerts an effect, not total level. When is this particularly important?

A

If drug is highly bound to albumin (>90%)
Has a small volume of distribution
Has a low therapeutic ratio

167
Q

What is a class 1 (object) drug?

A

Used at lower dose than no. of albumin binding sites

168
Q

What is a class 2 (precipitant) drug?

A 
Used at doses greater than number of albumin binding sites, and thus displaces class 1 (object) drug.
Free drug levels of object drug will rise transiently, as will its elimination rate.
169
Q

What drugs may act as class 2/precipitant drugs to warfarin?

A

Sulfonamides, aspirin, phenytoin

170
Q

What drugs may act as class 2/precipitant drugs to tolbutamide?

A

Sulfonamides, aspirin

171
Q

What drugs may act as class 2/precipitant drugs to phenytoin?

A

Valproate

172
Q

What happens is a patient is taking an object drug, and then adds in a precipitant drug as well?

A

Patient will temporarily have higher levels of free object drug - increasing risk of toxicity. Elimination rate of object drug in patient will also rise though, steady state is restored after a few days.

173
Q

What does a drug with 1st order kinetics mean?

A

Rate of elimination is proportional to drug level. Constant fraction of drug eliminated per unit time, half life can be defined.

174
Q

What does a drug with 0 order kinetics mean?

A

Rate of elimination is constant (rare)

175
Q

When is a steady state of drug metabolism established?

A

Within 5 half lives of that drug

176
Q

What is a loading dose?

A

A large initial dose of a drug used to quickly get drug within therapeutic range

177
Q

What are the 2 phases of liver metabolism?

A
  1. Oxidation, reduction, hydrolysis, by mixed function oxidases.
  2. Conjugation (glucuronide, Acetyl, methyl, sulphate)
178
Q

What is the enzyme used in 1st phase of liver metabolism of a drug?

A

Cytochrome P450 reductase

Has low substrate specificity, affinity for lipid soluble drugs. Inductively and inhibitable

179
Q

Drug interactions are most likely to matter clinically if…

A

Involves drugs with a low therapeutic ratio
Drug is being used at minimum effective concentration e.g. Oral contraceptive
Drug metabolism follows 0 order kinetics

180
Q

What is phenobarbitone a metabolic inducer of?

A

Warfarin, phenytoin

181
Q

What is rifampicin a metabolic inducer of?

A

Oral contraceptive

182
Q

What is cigarette smoke a metabolic inducer of?

A

Theophylline

183
Q

What is cimetidine a metabolic inhibitor of?

A

Warfarin

184
Q

What drugs do you have to be particularly careful of?

A

Drugs with a low therapeutic ratio

185
Q

What is passive reabsorption of a drug dependent upon?

A

pH

Only the non-ionised moiety is lipid soluble so can cross membranes easily

186
Q

For weak acid drugs, acidic urine has what effect upon reabsorption of drug?

A

Increases absorption

187
Q

For weak acid drugs, alkaline urine has what effect upon reabsorption of drug?

A

Decreases reabsorption

188
Q

For weak base drugs, acidic urine has what effect upon reabsorption of drug?

A

Decreases absorption

189
Q

For weak base drugs, alkaline urine has what effect upon reabsorption of drug?

A

Increases reabsorption

190
Q

What is the effect of kidney disease on the half life of drugs?

A

Half life is prolonged - Lower maintenance dose

191
Q

What, with regards to drugs, can be altered by kidney disease?

A

Longer half life - therefore takes longer to reach stable state
Protein binding can be altered (due to loss of protein)

192
Q

Give 2 ways cholesterol may stabilise the plasma membrane

A

Intercalation of the rigid planar conjugated ring structure reduces phospholipid packing, therefore increasing fluidity.
Rigid conjugated ring structure reduces phospholipid aliphatic tail mobility, so reducing fluidity.

193
Q

Describe 2 ways a membrane protein may interact with the hydrophobic domain of a membrane bilayer

A

Transmembrane sequence of ~20-22 amino acids with hydrophobic R-groups (often in alpha helix structure)
Lipid-linked proteins through insert action of hydrophobic lipid moiety e.g. Post-translational modification with fatty acid e.g. G-proteins

194
Q

Give an example of a passive transporter that transports K+ ions

A

ROMK (in kidney)

195
Q

Name the transporter inhibited by loop diuretics and their location in the kidney tubule

A

Na+/K+/2Cl- cotransporter

Thick ascending limb

196
Q

What is the approximate resting membrane potential of a nerve cell?

A

-70mV

197
Q

How is the approximate resting membrane potential of -70mV within a nerve cell maintained?

A

Efflux of K+ via voltage-insensitive K+ channels

Aaaaand minor leak of Na+/Ca2+ ions

198
Q

What property does the absolute refractory period confer on nerve cells?

A

Prevents re-entrant excitation, directional impulse propagation

199
Q

What happens to conduction of a nerve impulse in a neurone immediately after the loss of the myelin sheath?

A

Conduction failure due to increased neuronal membrane capacitance and current leak preventing no dally distributed channels from being raised to threshold value

200
Q

What happens to conduction of a nerve impulse in a neurone after a period of recovery from the loss of the myelin sheath?

A

Re-establishment of nerve impulses, with slower conduction velocity, due to redistribution of nodal ion channels in the nerve membrane

201
Q

Describe signal transduction by insulin receptors on binding of insulin

A

Insulin India to receptor, resulting in conformational change, which activates integral tyrosine kinase within the cytoplasmic domain.
Receptor autophosphorylation
Binding of transducing protein (insulin receptor substrate IRS) via specific domains which recognise phosphotyrosine residues on receptor
Tyrosine phosphorylation of IRS and consequent binding and activation of effector enzymes
Activation of intracellular enzymes by tyrosine phosphorylation

202
Q

What is homologous desensitisation?

A

The process by which ONLY the signal from the stimulated receptor is reduced

203
Q

What is heterologous desensitisation?

A

The process by which receptors for several agonists become less effective even when only one has been continuously stimulated

204
Q

What receptor subtype activation results in dilatation of airways smooth muscle

A

Beta 2

205
Q

What receptor subtype activation results in negative chronotrophy of the SAN?

A

M2

206
Q

What receptor subtype activation results in positive ionotrophy of the heart ventricle?

A

Beta 1

207
Q

What receptor subtype activation results in the stimulation of glandular secretions ?

A

M3 (and some M1)

208
Q

What is the GTP-binding protein activated by alpha1-adrenoceptors, and results in release of Ca2+ from intracellular stores?

A

Gq

209
Q

What is the effector activated by the G-protein Gq?

A

Phospholipase C

210
Q

What does IP3 stand for?

A

Inositol-1,4,5-triphosphate

211
Q

How is IP3 signal terminated?

A

IP3 phosphatase converts IP3—->IP2 (inactive)

212
Q

Why is movement of protein in lipid bilayers more restricted than that of lipid constituents?

A

Proteins for membrane protein associations, may reduce rotation and lateral movement
Proteins form associations with peripheral membrane proteins e.g. Cytoskeleton
Lipid mediated effects - proteins separate out into fluid phase of bilayer in cholesterol poor areas

213
Q

What proportion of fluid in the body is intracellular/extracellular?

A

~3/4 Intracellular (28l)
~1/4 Extracellular (9.4l)

Approx 4.6l in blood plasma

214
Q

What does NCX stand for?

A

Sodium calcium exchanger

215
Q

Apart from glucose, what other metabolites use the sodium gradient for their uptake into cells against the concentration gradient?

A

Amino Acids

216
Q

What are the consequences for conduction of the nervous impulse of demyelination that is partial?

A

Slower conductance

217
Q

What are the consequences for conduction of the nervous impulse of demyelination that is complete?

A

No conductance

218
Q

What can desensitisation of GPCRs result from?

A

Modification of the receptor by phosphorylation
Reversible receptor internalisation
Down-regulation

219
Q

Are parasympathetic preganglionic neurones long or short?

A

Long

220
Q

Are parasympathetic postganglionic neurones long or short?

A

Short

221
Q

Are sympathetic preganglionic neurones long or short?

A

Short

222
Q

Are sympathetic preganglionic neurones long or short?

A

Long

223
Q

Where do parasympathetic neurones originate?

A

Lateral horn of the medulla and sacral regions of the spinal cord

224
Q

Where are parasympathetic ganglia found?

A

Located in tissues innervated by the postsynaptic fibres

225
Q

Where do sympathetic nerves originate?

A

Lateral horn of the lumbar and thoracic spinal cord

226
Q

Where are sympathetic ganglia located?

A

In the paravertebral chain close to the spinal cord

227
Q

What receptors are activated upon release of ACh by a preganglionic nerve?

A

Nicotinic ACh (ligand gated ion channel)

228
Q

What are the 2 major classes of adrenoceptor NA interacts with?

A

Alpha and beta

229
Q

What subdivisions can alpha adrenoceptors be divided into?

A

Alpha 1 and alpha 2

230
Q

What subdivisions can beta adrenoceptors be divided into?

A

Beta 1, beta 2, and beta 3

231
Q

What type of receptor are all adrenoceptors?

A

G protein coupled receptors

232
Q

What might some non-adrenergic, non-cholinergic transmitters release? (Or co-release along with NA/ACh)

A

ATP
NO
Neuropeptides
Serotonin

233
Q

How might chromaffin cells be considered?

A

Post ganglionic sympathetic neurons that do not project to a target tissue

234
Q

Where are chromaffin cells found?

A

Adrenal glands

235
Q

What are the basic steps in neurotransmission?

A
  1. Uptake of precursors
  2. Synthesis of transmitter
  3. Vesicular storage of transmitter
  4. Degredation of transmitter
  5. Depolarisation by propagated action potential
  6. Depolarisation-dependent influx of Ca2+
  7. Exocytosis release of transmitter
  8. Diffusion to post-synaptic membrane
  9. Interaction with post-synaptic receptors
  10. Inactivation of transmitter
  11. Re-uptake of transmitter
  12. Interaction with pre-synaptic receptors
236
Q

What enzyme catalyses ACh synthesis?

A

Choline acetyltransferase (CAT)

237
Q

What enzyme catalyses acetylcholine degredation?

A

(Acetyl) Cholinesterase (AChE)

238
Q

What is the equation for Acetylecholine synthesis?

A

Acetyl CoA + Choline —> Acetylcholine + Coenzyme A

239
Q

What is the equation for acetylcholine degradation?

A

Acetylcholine —> Acetate + Choline

240
Q

What might lack of selectivity of a drug result in?

A

Side effects

241
Q

Describe the structure of most post-ganglionic sympathetic neurons

A

Highly branched axonal network with numerous varicosities, each of which is a specialised site for Ca2+ dependent noradrenaline release

242
Q

Describe noradrenaline synthesis

A

Tyrosine—>DOPA—>Dopamine—>Noradrenaline

243
Q

Describe the mechanisms of termination of noradrenaline transmission

A

Uptake 1: NA actions terminated by re-uptake into pre-synaptic terminal by a Na+ dependent, high affinity transporter
Uptake 2: NA not recaptured via uptake 1

244
Q

What enzymes are used to metabolise noradrenaline in the pre-synaptic neurone?

A 
Monoamine oxidase (MAO)
Catechol-o-methyltransferase (COMT)
245
Q

What are the mechanisms for modulating NA transmission?

A
  • Presynaptic GPCR by inhibiting Ca2+ dependent exocytosis
  • Indirectly acting sympathomimetic agents, taken into vesicles, displacing NA which then leaks out by mechanism other than Ca2+ mediated release
  • Uptake 1 inhibitors. Work primarily in the CNS
  • Adrenoceptor agonists and antagonists
246
Q

What can be used to treat asthma/oppose bronchoconstriction?

A

Beta2-Adrenoceptor selective agonists (e.g. Salbutamol). Minimal side effects as are subtype-selective

247
Q

How do beta2 agonists, e.g. Salbutamol, cause bronchiodilation?

A

Receptors are coupled to G-protein of Adenylyl cyclase, which produces second messenger cyclic AMP, which decreases Ca2+ concentrations within cells, and activates protein kinase A. Both of this inactivated myosin light chain kinase, and activate myosin light chain phosphatase.
Can also open Ca2+ activated K+ channels, thereby hyperpolorising airway smooth muscle cells

248
Q

What is an endogenous substance?

A

Naturally occuring in the body

249
Q

What is an exogenous substance?

A

An administered compound, I.e. A drug

250
Q

What type of drug is it easy to predict response for?

A

Drugs with 1st order kinetics

251
Q

If a drug is potent, what does this mean?

A

Has a greater response at a lower drug concentration

252
Q

What is tachyphylaxis?

A

Reduced sensitivity to a drug as a result of excessive exposure to agonist

253
Q

Via what mechanisms could altered sensitivity to a drug arise?

A

Change in receptor number
Change in receptor coupling to second messengers
Change in the availability of second messengers
Change in cell responsiveness

254
Q

What receptors are activated in by opiates?

A

Gamma-opioid receptors

255
Q

What is tamoxifen used for?

A

Oestrogen-receptive Breast cancer

256
Q

Why is tamoxifen so beneficial?

A

Selective oestrogen modulator. Different action depending on tissue receptor - acts as an antagonist at the breast, but an agonist at bone and uterus.

257
Q

What is phaeochromocytoma?

A

Tumour of the adrenal medulla

258
Q

What does phaeochromocytoma cause?

A

Intermittent increased secretion of catecholamines (adrenaline/noradrenaline)
Therefore intermittent signs and symptoms of sympathetic nervous system over activity (sweating, tremor, anxiety, high blood pressure)

259
Q

What is the risk of sudden removal of beta blockers in treatment of angina?

A

Suprasensitivity may have developed (beta receptor up-regulation). Symptoms would get significantly worse.

260
Q

How is age associated with catecholamine sensitivity?

A

Decreasing sensitivity to endogenous catecholamines
Reduced heart rate responsiveness to exogenously administered catecholamines
Potential excess pharmacological efficacy of administered drugs

261
Q

What does Gs bring about?

A

Adenylyl cyclase activation

262
Q

What does Gt bring about?

A

GMP phosphodiesterase (in visual excitement)

263
Q

What does Gi bring about?

A

Adenylyl cyclase inhibition (activation of K+ channels)

264
Q

What does Gq bring about?

A

PIP2 activation (M3 smooth muscle contraction)

265
Q

How does cholera toxin work?

A

ADP ribosylation by cholera toxin prevents GTP hydrolysis by alpha subunit

266
Q

How does pertussis toxin work?

A

ADP ribosylation by pertussis toxin prevents receptor G-protein interaction

267
Q

How is the actin-spectrin network of the erythrocyte cytoskeleton attached to the membrane?

A

By adapted proteins ankyrin and glycophorin

268
Q

What specifically does PMCA transport?

A

2H+ in for 1Ca2+ out

Requires hydrolysis of ATP

269
Q

Give an example of a depolarising nAChR blocker

A

Succinylcholine

270
Q

What do trigger proteins do?

A

Bond to Ca2+ and alter function e.g. Synaptotagmin

271
Q

What do Ca2+ buffers do?

A

Regulate free Ca2+

272
Q

How are ionotropic receptors activated?

A

By a ligand/agonist binding

273
Q

What are ‘classical’ ligand-gated channels like?

A

Pentameric (2xalpha, beta, gamma and delta subunits)

274
Q

How do membrane bound receptors with integral enzyme activity exist?

A

In dimers

275
Q

What are membrane bound receptors that signal through transducing proteins always?

A

7TMD

E.g. GTP binding proteins

276
Q

Where is cyclic GMP phosphodiesterase found?

A

Found in photoreceptive cells of retina (rods and cones)

277
Q

What does cyclic GMP phosphodiesterase do?

A

Regulates breakdown of 2nd messenger cGMP on activation by Gt, following excitation of rhodopsin by a photon of light.
On exposure to light, activation causes a decrease in cGMP, leading to channel closure and membrane hyperpolarisation, thus altering signal output to CNS

278
Q

What is buprenorphine

A

Partial agonist of of morphine - higher affinity for receptors but lower efficacy

279
Q

What drug is filtered in the kidney?

A

Only free unbound drug is filtered through the glomerular tuft?

280
Q

What drug actually exerts an effect in the body?

A

Only free unbound drug (not the total level!)

281
Q

How many mACh receptor subtypes are there?

A

5

282
Q

What is sludge syndrome?

A

Over activity of the parasympathetic nervous system

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