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Anaesthetic FRCA Primary - Teaching Days > AWABS - Enzymes and Nuclear receptors > Flashcards

AWABS - Enzymes and Nuclear receptors Flashcards

1
Q

Methods by which drugs work

A

Physico-chemical properties
Receptor interaction
Enzyme interaction

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2
Q

Examples of medications which work via physico-chemical properties

A

Mannitol
Chelators - eg sugammadex

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3
Q

Examples of receptor types which can be targeted by medications

A

Ionic channels
Metabotropic receptors eg cyclic amp G protein coupled

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4
Q

Enzyme definition

A

Biological catalyst which speeds up reaction but not consumed within the reaction itself

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5
Q

Carbonic anhydrase enzyme catalyses which reaction

A

CO2 + H2O -> H2CO3 -> H+ + HCO3-

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6
Q

Location of carbonic anhydrase

A

Widespread inc:
RBCs
Eye
Stomach
Pancreas
Kidney

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7
Q

Role of carbonic anhydrase

A

Allows respiratory and metabolic / renal systems to compensate for acid-base imbalance

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8
Q

Example of carbonic anhydrase inhibitor

A

Acetazolamide

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9
Q

Examples of reversible enzyme inhibitors

A

ACEi
Neostigmine
Allopurinol
Carbidopa

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10
Q

Examples of irreversible enzyme inhibitors

A

Aspirin (COX-2)
Organophosphates
MAO inhibitors
PPI

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11
Q

Commonly used drugs which enhance enzyme activity

A

None common

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12
Q

Common enzymes which are increased in NUMBER (not activity) by drugs

A

Cytochrome P450 class

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13
Q

Novichok mechanism of action

A

Group of agents which irreversibly inhibit acetylcholinesterase

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14
Q

Short acting acetylcholinesterase inhibitors

A

Eg Edrophonium

Used to diagnose myasthenia gravis and differentiate from “myasthenic” and “cholinergic crisis” (Tensilon test)

Binds weakly to serine site of acetylcholinesterase and causes allosteric change

Duration of 10-30 mins

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15
Q

Medium acting acetylcholinesterase inhibitors

A

Eg Neostigmine

Duration of action 2-3 hours – well matched to exceed half life of NDMR

Routine reversal of neuromuscular blockade and treatment of MG

Binds esteratic site of Acetylcholinesterase

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16
Q

Long-acting acetylcholinesterase inhibitors

A

Eg Ecothiopate – only clinical application

Novichok is another example, along with other organophosphates

Seen in pesticides and chemical warfare

Stable and irreversible covalent integration to enzyme acetylcholinesterase

17
Q

Neostigmine structure

A

Has quaternary nitrogen and therefore polar

Does not cross blood brain barrier

18
Q

Physostigmine structure

A

Has a tertiary nitrogen and less polar

Has CNS effects

19
Q

Muscarinic symptoms

A

(SLUDGE M)

Seen with organophosphate / long acting acetylcholinesterase inhibition:
* Salivation
* Lacrimation
* Urination
* Diarrhoea
* GI upset
* Emesis
* Miosis

20
Q

Cholinergic symptoms

A

Severe weakness
Inc respiratory muscle weakness - SOB

21
Q

Michaelis-Menten equation

A

V= rate of reaction
V max = max possible rate of reaction
[S] = substrate concentration
Km is a constant

22
Q

Michaelis-Menten equation use

A

Predicts rate of a biological reaction according to the concentration of substrate and the characteristics of the enzyme involved

23
Q

Interpretation of Michaelis-Menten equation at low substrate concentrations

A

At low substrate concentrations the “+ [S]” aspect becomes negligible and equation becomes Vmax/Km (which is a constant) x [S].

Therefore V is proportional to substrate concentration – This is First order reaction (rate is proportional to substrate concentration)

24
Q

Interpretation of Michaelis-Menten equation at high substrate concentrations

A

The Km constant becomes almost insignificant.

Therefore increasing substrate concentration will no longer increase rate of reaction.

This is Zero order reaction.

Tendency for substrate accumulation in these reactions

25
Q

Examples of Zero order reactions

A

Phenytoin
Alcohol
Warfarin
Amiodarone

26
Q

Michaelis-Menten graph

A
27
Q

Zero order reaction graph

A
28
Q

Example of drug / hormone which acts at nucleus receptor

A

Thyroid hormones and glucocorticoids

T4 main storage form, T3 active form which transports across lipid bilayer
Alters protein, carbohydrate and fat metabolism
Controls basal metabolic rate

29
Q

Features that drugs / hormones acting at nuclear receptors require in order to pass through cell membrane

 

A

Non-polar / non-charged
Small and lipid soluble

Anaesthetic FRCA Primary - Teaching Days (64 decks)

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