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IDM > TBL 6 - DRUG TARGETS > Flashcards

TBL 6 - DRUG TARGETS Flashcards

1
Q

What are the 4 main types of receptors known as receptors?

A

1) Ligand gated ion channels
2) G protein coupled receptors
3) Kinase receptors
4) Nuclear/intracellular receptors

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2
Q

What are ligand gated ion channels?

A

Also known as ionotropic receptors.
Receptors directly coupled to ion channels.

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3
Q

What are the 4 examples of these receptors?

A

Examples of these receptors include:
- Nicotinic
- GABAa
- GABAc
- Glutamate receptors
All fast acting and involved with neurotransmission

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4
Q

What are the endogenous agonist for nicotinic receptor?

A

Endogenous agonist for nicotinic receptor is acetylcholine (Ach).

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5
Q

Where are nicotinic receptors found and where does it occur?

A

Nicotinic receptors found on plasma membranes of cell and one of the most numerous receptors in the body.
Occur in neuromuscular junction (NMJ), in autonomic ganglia and in CNS.

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6
Q

What are the 4 different subunits in receptors?

A

Most studied nicotinic receptor one that occurs in electroplax organ of the torpedo California electric fish.
Receptor made up of a pentamer of 4 different subunits:
1) 2 x a (40KD)
2) B (49 KD)
3) E (57 KD)
4) δ (65 KD)

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7
Q

What does Ach bind to, to trigger a response?

A

Ach binds to a-subunits in order to trigger receptor.

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8
Q

What type of selectivity does agonist show and what drug is the exception to this.

A

Agonists shows little selectivity between nicotinic receptors occurs in different locations, different from each other pharmacologically.
Drug decamethonium exception to this rule, since it’s a potent agonist at the NMJ, but weak antagonist on autonomic ganglia.

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9
Q

What type of selectivity does antagonist show and what type of drugs affect NMJ and automatic ganglia and CNS?

A

Antagonists, show strong selectivity’s since very low concs of B-bungarotoxin blocks NMJ nicotinic receptors, but has no effect on autonomic ganglia.
Mecamylamine is antagonist in CNS and on autonomic ganglia has no effect on NMJ.

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10
Q

In what time period does ligand binding channel open?

A

Ionotropic receptors, ligand binding and channel opening occur on a millisecond time scale.

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11
Q

What is the function of ligand gated ion channel happens? What happens when Ach binds to nicotinic receptor?

A

1) When Ach binds to a nicotinic receptor, causes ion channel to open very quickly, which increases plasma membranes Na+/K+ permeability so depolarising cell and increasing probability that action potential will be generated.
2) Inward rush of Na+ ions, down conc gradient, responsible for depolarisation.
3) Intracellular side of plasma membrane is negatively charged compared to extracellular surface. So inward rush of positively charged Na+ ions will reduce this - membrane potential, depolarising the cell.
4) Found motor endplate nicotinic receptor channels only open for 1-2 millisecs, equivalent to influx of 1 x 10^7 ions per sec per channel.

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12
Q

What is the function of NMJ?

A

Function of NMJ to transmit action potentials conducted along motor (Somatic) nerves across the synaptic clefts that occur in motor endplates.

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13
Q

What does the postsynaptic region contain?

A

Postsynaptic region of sarcolemma contains many invaginations, which increases total surface area of membrane in region, thus increasing its exposure to Ach.

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14
Q

Where does Ach synthesis occurs and what is it catalysed by?

A

Ach synthesis occurs in motor neurone terminal and is catalysed by cytosolic enzyme choline acetyltransferase (C.A.T.).

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15
Q

What are the acetyl groups donated by?

A

Acetyl groups donated by acetyl coenzyme A (acetyl CoA) which are covalently bonded to choline to form Ach.

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16
Q

Where is Ach stored and when is it ready for release?

A

Ach stored in vesicles, ready for release.

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17
Q

Where is action potentials conducted and what happens when depolarisation occurs?

A

Action potentials conducted along motor nerves reach their nerve terminal, depolarisation causes an influx Ca^2+ ions, which triggers Ach release into the synaptic cleft, as vesicles now fuse with terminal membrane.

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18
Q

What happens when Ach is released?

A

Released Ach diffuse across synaptic cleft, bind to nicotinic receptors on sarcolemma, causing a depolarisation, which can stimulate an action potential in muscle fibre causing it to contract. - Endplate potential or EPP.

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19
Q

What happens in Ach in the synaptic cleft? (hint: hydrolyses)

A

Ach in synaptic cleft also interacts with the enzyme acetylcholinesterase, which hydrolyses it to choline and acetic acid.
Process occurs the whole time Ach is present in synaptic cleft.

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20
Q

What happens when no Ach is being released?

A

When no Ach being released from neurone terminal, acetylcholinesterase reduced synaptic conc of Ach, terminating the response evoked.

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21
Q

What are the nicotinic agonist at NMJ (4 things)?

A
  • Ach
  • Nicotine
  • suxamtheonium
  • decamethonium
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22
Q

What are the nicotinic agonist at autonomic ganglia (4 things)?

A
  • Ach
  • Nicotine
  • Lobeline
  • Epibatidine
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23
Q

What are the nicotinic antagonist at NMJ (5 things)?

A
  • Tubocucarine
  • Pancuronium
  • B-Bungarotoxin
  • Atracurium
  • Vecuronium
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24
Q

What are the nicotinic antagonist at automonic ganglia (2 things)?

A
  • Trimetaphan
  • Hexamethoium
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25
Q

What is the definition of an agonist?

A

Agonist = a substance which initiates a physiological response when combined with a receptor.

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26
Q

What is the definition of an antagonist?

A

Antagonist = a substance which interferes with or inhibits the physiological action of another.

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27
Q

What are the agents that reduce Ach release (4 things)?

A
  • Hemicholium
  • Botulinum toxin
  • Mg2+, Mn2+ and CO2+ ions
  • Aminoglycoside antibiotics
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28
Q

What are the competitive neuromuscular blocking agents (6 things)?

A
  • Tubocurarine
  • Gallamine
  • Pancuronium
  • Alcuronium
  • Atracurium
  • Vecuronium
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29
Q

What are the depolarising neuromuscular blocking agents (2 things)?

A
  • Suxamethonium
  • Decamethonium
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30
Q

What are the transmission potentiating agents (8 things)?

A
  • Anticholinesterase
  • Pyridostigmine
  • Neostigmine
  • Distigimine
  • Ambenonium
  • Physostigmine (eserine)
  • Dyflos
  • Edrophonium
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31
Q

What are the choline carrier inhibiting agent (1 thing)?

A
  • Hemicholinum
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32
Q

What agent is used for Ach release enhancing agents (1 thing)?

A
  • 4-aminopyridine
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33
Q

What is tubocurarine and what do native Indians use this for?

A
  • Tubocurarine found as mixture of alkaloid substances called ‘curare’ extracted from the chondrodendron tomentosum plant that grows in the rain forests of south America.
    Native Indians use curare to treat their arrow tips before using them for hunting.
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34
Q

What is Myasthenia gravis and what symptoms can occur?

A

Chronic disease characterised by an abnormal fatigability and weakness of skeletal muscles, which chiefly affects adolescents and young adults (under 40 years old).
Symptoms include ptosis (drooping of upper eyelid), double vision, and dysarthria (a speech disorder in which pronunciation is unclear).
Autoimmune disease affecting neuromuscular transmission.
IgG antibodies cause loss of nicotinic receptors in NMJ.
Fatigue experienced might become extreme that muscles become temporarily paralysed.

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35
Q

What is the treatment for myasthenia gravis?

A

Administering anticholinesterases
Using prednisolone or azathioprine
Performing plasmaphoresis and surgically removing the thymus

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36
Q

What is G-protein coupled receptor?

A

GPCR also called metabotropic, 7-transmembrane spanning receptors

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37
Q

What are examples of GPCR?

A

Examples include:
- Muscarinic
- Adrenergic
- Dopaminergic
- 5-hydroxytryamine (5-HT)
- Purine (adenosine, ATP)
Opiate receptors

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38
Q

What does GPCR structure consist of?

A

Consists of 7 transmembrane spanning regions that are connected by extracellular/intracellular loops.
Receptors are 3D structures that arrange their extracellular loops and some of the transmembrane regions into pockets that can accept ligands.
Extracellular domains of GPCRs varied, so large number of diverse receptors exist, all with different affinities for ligands.
Domain contains disulphide bonds, which maintains 3D structure.

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39
Q

How do G-proteins get their name?

A

Get their name from the guanine nucleotides GDP and GTP.

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40
Q

What are G-proteins made up of?

A

G-proteins made up of alpha-, beta- and gamma-subunits.

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41
Q

Which subunits form complexes together in G-protein?

A

Beta- / gamma-subunits form complex together, since they’re hydrophobic, found residing in cells plasma membrane, where able to freely move about.

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42
Q

What are the 3 properties in alpha subunits?

A

1) Can bind to guanine nucleotides
2) Forms a loose association with beta/gamma complex
3) Has the ability of catalysing the hydrolysis of GTP to GDP.

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43
Q

What are the 5 processes of G-protein?

A

1)When agonist binds to its receptor, a conformation change is induced within receptor enables alpha-subunit binding.
2) Once bound, alpha-subunit releases GDP and binds instead to GTP.
3) Activated alpha-subunit now completely dissociates from the receptor and its beta/gamma complex, allowing it to diffuse across the membrane surface to stimulate its target.
4) By associating with target alpha-subunit’s GTPase activity increased, so bound GTP is hydrolysed to GDP and an inorganic phosphate group, terminating alpha-subunits activation.
5) Alpha-subunit can be re-associate with beta/gamma complex and process can be repeated.

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44
Q

What is an advantage of GPCRs?

A

1) GPCRs are not rapidly acting as ionotropic receptors, advantage is they can amplify a signal.
2) One agonist/receptor complex can activate several alpha-subunits and in turn stimulate targets producing amplification.
3) Stimulation of GPCRs produce wither stimulatory or inhibitory effects, determines what sort of receptor is controlling what type of target.

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45
Q

What are the 3 catagories of G-proteins?

A

G-proteins has 3 categories:
1) Gs
2) Gi
3) Gq

  • Gs/Gi proteins produce either simulation or inhibition of their targets.
  • Activated Gq proteins activate phospholipase C
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46
Q

What are the 3 main targets of G-proteins?

A
  • Ion channels
  • Adenylate cyclase/cyclic AMP (cAMP) system
  • Phospholipase C/inositol phosphate system
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47
Q

Where are muscarinic receptors found?

A

Muscarinic receptors, named after drug muscarine (extracted from amanita muscria mushroom) found on cells/tissues inverted by the parasympathetic nervous system.

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48
Q

What happens to the cardiovascular system when Ach binds to muscarinic receptors?

A

1) Ach (cholinergic) binds to muscarinic receptors.
2) Cholinergic receptors divided into nicotinic and muscarinic subtypes.
3) Parasympathetic nervous system (PNS) can be thought of as the body’s resting and digesting system so muscarinic receptors of the heart are stimulated e.g by vagus nerve releasing Ach or by drugs), reduces heart rate and force of contraction.

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49
Q

What type of agonists act on muscarinic receptors?

A
  • Ach
  • Carbachol
  • Pilocarpine
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50
Q

What type of antagonists act on muscarinic receptors?

A
  • Atropine
  • Hyosine
  • Ipratropium
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51
Q

What are the processes of the muscarinic receptors (4 steps)?

A

1) Muscarinic receptors found in cardiac muscle cells known to increase membrane permeability to K+ ions, which reduces rate/force of contraction.
2) Once Ach binds to muscarinic receptors, activated G-proteins can open K+ channels.
3) K+ ions diffuse out of cell down their conc gradient, intracellular looses + charge and becomes - charged.
4) Hyperpolarisation make tis harder for cells to depolarise and contract.

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52
Q

What are subtypes of the adrenergic receptors?

A

This class can be divided into α and β- subtypes, which can then be further divided into α1, α2, β1 and β2 subtypes.

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53
Q

What is adrenergic receptors involved with and what happens when adrenergic receptors are stimulated on the heart?

A

adrenergic receptors are generally involved with the sympathetic nervous system.
The effects of sympathetic stimulation can most easily be remembered by thinking about the “fight or flight” response.
So when the adrenergic receptors on the heart are stimulated, rate and force of contraction increase.

54
Q

What does a1-adrenoreceptors found and cause?

A

α1-adrenoceptors are generally stimulatory and in blood vessels will cause a vasoconstriction.

55
Q

What does a2-adrenoreceptors found and cause?

A

α2-adrenoceptors are generally found on presynaptic nerve terminals and negatively feedback on neurotransmitter release.

56
Q

What does B1-adrenoreceptors found and cause?

A

β1-adrenoceptors are mostly concentrated in cardiac tissue and stimulate the heart to beat faster and with more force.

57
Q

What does B2-adrenoreceptors found and cause?

A

β2-adrenoceptors generally induce tissues to relax e.g., bronchodilation in lung airways and vasodilatation in blood vessels that supply muscles

58
Q

What kind of system does adrenoreceptors?

A

adrenoceptors use a system of “second messengers”.

59
Q

What are second messengers?

A

Second messengers are agents whose intracellular concentrations vary, depending on the levels of receptor stimulation.
These agents, once produced or released, can diffuse away from the cell membrane to alter the rate at which cellular processes occur within the cell.

60
Q

What are common second messengers?

A

Common second messengers include Ca2+ ions, cyclic adenosine monophosphate (cAMP), inositol-1, 4, 5-triphosphate (InsP3) and diacylglycerol (DAG).

61
Q

What forms when B-adrenoreceptors are stimulated, after its formation what does it activate?

A

So, for example, when β-adrenoceptors are stimulated, cAMP is formed from ATP by the enzyme adenylate cyclase.
cAMP then activates the enzyme protein kinase A, which then phosphorylates proteins (enzymes, muscle fibres, ion channels etc.) to produce a physiological effect.

62
Q

The kinase linked receptors uses what amino acid?

A

Receptors linked to tyrosine kinase.

63
Q

What is the most well known ligand that binds to kinase receptor?

A

Most well know ligand that binds to kinase receptor is insulin
Other ligands for these receptors include different growth factors.

64
Q

What are kinase linked receptors bound to?

A

Kinase linked receptors found bound to membranes.

65
Q

What type of domains do kinase linked receptors possess?

A

Kinase-linked receptors possess extracellular/intracellular domains with each domain containing between 400-700 amino acid residue’s.

66
Q

What are 2 domains connected together by?

A
  • 2 domains connected together by single alpha helix that spans the thickness of the membrane.
67
Q

What is the extracellular domain of insulin receptor made from and how is it attached?

A

For example the extracellular domain of insulin receptor made from a single polypeptide chain that is then attached, via disulphide bridges, to a 2nd polypeptide chain that forms transmembrane spanning alpha helix and intracellular domain.

68
Q

What do kinase receptors bind to?

A

Kinase receptors bind growth factors are constructed from a single long polypeptide chain, which can be over 1000 residues long.

69
Q

What do extracellular and intracellular domain form?

A

Extracellular domains form receptors ligand binding sites, while intracellular form tyrosine kinase domains.

70
Q

What is kinase enzymes responsible for?

A

Kinase enzymes responsible for catalysing the phosphorylation of cellular components.
Process requires source of phosphate groups, which bound ATP can provide.

71
Q

What does ligand binding result in?

A

Ligand binding results in ‘dimerization’ of receptors (a process in which 2 receptors pair up together to form a dimer).

72
Q

What is the process autophosphorylation?

A

When this happens, process of autophosphorylation occurs which means tyrosine residues of intracellular domains becomes automatically phosphorylated, with phosphate groups being donated by bound ATP.
Phosphorylated tyrosine’s now become high affinity binding sites for intracellular proteins.

73
Q

What does intracellular proteins interact with?

A

Intracellular proteins interact with kinase receptors contain highly conserved ‘SH2’ domains.

74
Q

How many amino acid residues do SH2 domains contain?

A

Domain contains 100 amino acid residues, their name derived from ‘Src-homology’ first identified in products obtained from Src oncogenes.

75
Q

What are oncogenes?

A

Oncogenes is mutated or over-expressed version of a normal gene in a cell, which is free from normal growth restraints, so converting cell into tumour cell.

76
Q

What does SH2 proteins bind to?

A

SH2 proteins bind to kinase-linked receptors include enzymes such as protein kinases and phospholipases.

77
Q

What does growth factors trigger?

A

Growth factors trigger the activation of phospholipase C, stimulates production of diacylglycerol and inositol triphosphate.

78
Q

What are cytokines?

A

Cytokines are small proteins or biological factors that are released by cells and have specific effects on cell-to-cell interactions.

79
Q

What are cytokines important for?

A

Cytokines important for co-ordinating cellular communication and behaviour.

80
Q

What are cytokines convenient for?

A

Cytokines convenient to use for agents such as interleukins and signalling molecules such as tissue necrosis factor (TNF) and interferons.

81
Q

When cytokines ligands bind to receptors what occurs?

A

When cytokine ligands bind to these receptors, receptor dimerization occurs again, after which cytosolic tyrosine kinase units are the able to bind.
Following this, SH2 containing proteins bind and become activated, so producing the cellular response.

82
Q

What type of messenger is cGMP/cAMP?

A

Cyclic guanosine monophosphate (cGMP) is a 2nd messenger same as cAMP.

83
Q

What activator of guanylate cyclase enzyme catalyses the synthesis of cGMP?

A

Most famous activator of guanylate cyclase, enzyme catalyses the synthesis of cGMP, is nitric oxide.

84
Q

What is insulin produced by?

A

Insulin is polypeptide hormone (6,000 MW) produced by beta cells of islets of Langerhans in pancreas.

85
Q

What is insulin important for?

A

Insulin very important regulating blood glucose conc, with high blood sugar levels stimulating its secretion.

86
Q

What does insulin comprise of and what is their total molecular weight?

A

Insulin receptors comprises of 4 glycoprotein molecules, made up of 2 a- and 2 B-subunits and has total molecular weight of about 350,000.

87
Q

What does insulins subunits contain that enables for the formation of disulphide bridges?

A

Subunits contain cysteine residues that enable formation of disulphide bridges, which is important for keeping the complex bound together.

88
Q

Are a-subunits intracellular or extracellular and what does it form?

A

a-subunits of insulin receptor are extracellular and form insulin binding sites.

89
Q

Is the B-subunit extracellular or intracellular or both?

A

B-subunits have both extracellular/intracellular domains and their intracellular portion possesses tyrosine kinase activity.

90
Q

What happens to the B-subuint when insulin binds to receptor?

A

When insulin binds to its receptor, B-subunits autophosphorylation, which enhances kinase activity of other target proteins.

91
Q

How much percentage wise is needed to evoke the max response of insulin?

A

Less than 10% of insulin receptors have to evoke max response.

92
Q

What happens when insulin binds?

A

Insulin binds, cluster of ligand/receptor complexes form, which are internalised in vesicles.
Results in loss of insulin receptors from the cell surface, which may go some way to explain insulin resistance.

93
Q

What is insulins short term actions known to be and what is it governed by?

A

Insulins short-term actions considered to be its immediate metabolic effects, which are governed by regulating kinase and phospholipase enzymes via tyrosine kinase activity if the receptor.

94
Q

What does insulin trigger ad what does it increase and decrease?

A

Insulin triggers recruitment of glucose transporters, which increases glucose uptake by cells as well as increasing glycogen synthesis, reducing both gluconeogenesis and glycogen breakdown.

95
Q

What can activated insulin receptors trigger?

A

Activated insulin receptors may also trigger specific phospholipase C, which cleaves glycosylphosphatidylinositol.

96
Q

What does the cleavage from activated insulin form?

A

Cleavage forms DAG, but instead of inositol triphosphate being produced, inositol phosphoglycan (IPG) is formed instead.

97
Q

What does DAG activate?

A

DAG activates protein kinase C, whilst IPG regulates the activity of kinases enzymes.

98
Q

What are the insulin long term actions involved in regulating?

A

Insulins long-term actions involve regulating the synthesis of specific messenger RNA molecules, thus controlling the synthesis of important molecules such as enzymes, which in turn regulates cellular processes such as cell replication/proliferation.

99
Q

What are nuclear receptors involved in regulating and where can we find receptors?

A

Receptors are intracellular and involved with regulating DNA transcription.

100
Q

What are examples of nuclear receptors?

A

Steroid hormones, thyroid hormone and agents such as vitamin D and retinoic acid can ind to them.

101
Q

Where are neurotransmitters released from?

A

Neurotransmitters released from neurone terminals and transmit action potential signals across synapses.

102
Q

What are synapse and where do they occur?

A

Synapse are minute and occur between neurone terminals and wide variety of postsynaptic cells such as other neurones, muscle fibres and glands.

103
Q

What are hormones?

A

Hormones are substances produced by endocrine glands, passed into the blood, where they are distributed around the body to modify the structure or function of specific organs or tissues.

104
Q

What is an example of hormones?

A

Examples of hormones: sex hormones

105
Q

What is an example of a neurotrasmitter?

A

Examples of neurotransmitters: acetylcholine

106
Q

Where is adrenaline produced?

A

Chief hormone produced by medulla of adrenal glands.

107
Q

What is the function of adrenaline?

A

Function: preparing body for ‘flight or fight’ responses has widespread circulatory, muscular and metabolic effects.

108
Q

What sort of actions dose adrenaline induce?

A

Adrenaline will induce tachycardia and has positive ionotropic effect on the heart. Makes breathing easier, raises body’s metabolic rate, enhances muscular force of contraction and delays onset of fatigue.
Blood diverted away from non-essential area such as bladder and intestines.

109
Q

What are adrenergic nerves?

A

Nerves of sympathetic and autonomic nervous system were thought to act by releasing adrenaline at their terminals, called adrenergic nerves.

110
Q

Which adrenoreceptors is adrenaline an agonist for?

A

Adrenaline is agonist for a- and B-adrenoceptors

111
Q

How much amino acids residues does nuclear receptors contain?

A

Nuclear receptors are large monomeric proteins, containing between 400-1000 amino acid residues.

112
Q

What does the middle portion of molecule contain (hint: zinc)?

A

Middle portion of molecule contains highly conserved region of approx. 60 residues.
Contains 2 finger shaped loops of peptide chain, each being 15 residues long, which forms ‘zinc fingers’

113
Q

What ion does zinc fingers contain and how is it held in place?

A

Cus each finger contains a zinc ion, which is held in place by 4 cysteine residues.

114
Q

How are zinc fingers involved with DNA helixes?

A

Zinc finger domains forms the receptors DNA binding region since fingers are believed to be able to wrap around DNA helixes.

115
Q

What does the carboxyl and amino acid end of the nuclear receptor do?

A

Carboxyl (-COOH) end of protein contains steroid binding domain, whilst the amino (-NH2) end is the receptors regulatory domain that can activate the transcription of specific genes

116
Q

What do the ligands of nuclear receptors have to be in order for it to pass through the cells plasma membrane?

A

Nuclear receptors are intracellular, means their ligands have to be lipid soluble in order to pass through cell’s plasma membrane.

117
Q

What are steroid molecules mechanism of action in nuclear receptors (7 steps) ?

A

1) Steroid molecules highly lipid soluble and easily gain access to the intracellular compartment, where they can bind to their receptors located in the nucleus.
2) Steroid binds to receptor, induces a conformation change in which receptor unfolds to expose zinc finger domain.
3) Ligand/receptor complexes now bind to specific portions of DNA.
4) Binding positions well defined regions of DNA contain ‘hormone responsive elements’ or transcription factor activator proteins’ which occur approx. 200 base pairs upstream from the genes that are regulated.
5) Increases RNA polymerase activity, resulting in production of messenger RNA (mRNA).
6) mRNA leaves nucleus to form a complex with, enabling synthesis of protein.
7) Physiological responses maybe delayed by several hrs or even days, since whole process is relying on protein synthesis

118
Q

What are the 6 agents that bind to nuclear receptors?

A

Glucocorticoids, mineralocorticoids, sex hormones, thyroid hormones, vitamin D3 and retinoic acid are all agents that bind to nuclear receptors, interact with DNA and modify gene transcription.
Every type of tissue contains receptors that can bind to glucocorticoids and depending on cell type between 10-100 genes of each cell are steroid responsive

119
Q

What class of drugs are used to treat myasthenia gravis?

A

Class of drugs called anticholinesterases, which used to treat myasthenia gravis.

120
Q

What type of proteins are enzymes?

A

Enzymes are globular proteins that are catalysts of biological systems.

121
Q

What is a catalyst?

A

A catalyst is a substance that alters the rate at which a chemical reaction occurs, but itself not used up or changed by end of the reaction.

122
Q

What does a catalyst not alter?

A

Catalysts/enzymes don’t alter equilibrium position of a reaction nor increase product yield; can only alter rate at which the equilibrium is achieved.

123
Q

What happens when activation energy is absorbed?

A

Once AE has been absorbed, pushes energy levels of the reactants up to a point at which their random collisions are forceful enough to cause a reaction. - this can be done by increasing reactants temp but raising the temp too much results in denatured proteins.

124
Q

Enzymes allow reactions to occur without any abnormal increases in temp and they achieve this by lowering amount of AE required. How is this accomplished (2 ways)?

A

Accomplished by 2 ways:
1) Reducing the randomness of reactions by temporarily binding the reactants to the enzyme
2) Presenting the reactants to each other in the proper position for the reaction to occur.

125
Q

What are the 3 steps involved in working of enzymes?

A

1) Reactants (substrate’s), must bind to enzyme. Substrate binding occurs at particular site of the enzyme known as active site.
2) Enzyme-substrate complex undergoes an internal rearrangement to form product
3) Products of reaction are then released.

126
Q

How do substrates bind to enzymes?

A

Substrates bind to enzymes by weak attractions, such as H bonds, van der Waals forces, electrostatic attractions and hydrophobic interactions.

127
Q

What is a competitive inhibitor?

A
  • Reversible reaction
  • Involves substrate and inhibitor molecules competing for the occupancy of the enzymes active sites.
  • Many competitive inhibitors resemble the substrate and when occupying active site, prevents actual substrate from binding.
  • Competitive inhibitor diminishes rate of catalysis by reducing proportion of substrate molecules binding to enzymes.
128
Q

What is a non-competitive inhibitor?

A
  • Reversible reaction
  • Inhibitor and substrate can bind simultaneously to an enzyme cus they have separate binding sites and not in competition with each other for occupancy of the enzyme.
  • Non-competitive inhibition can’t be overcome by increasing the substrates conc.
  • Once inhibitor has bound to enzyme, conformation of substrates active site alters.
129
Q

What are carrier molecules?

A

-Plasma membranes made up of lipid bilayer.
- Means ions, naturally occurring molecules and drugs are too polar (insufficiently lipid soluble) to cross lipid bilayers on their own.
Polar particles require membrane carrier or transporter molecules gain access to intracellular compartments.

130
Q

What are 4 examples of carrier molecules?

A
  • Ion
  • Glucose
  • Amino acid transporters
  • Neurotransmitter re-uptake transporter molecules.
131
Q

Anticholinesterases drugs divided into 3 classes:

A
  • Short acting e.g. edrophonium
  • Medium duration acting e.g. physostigmine
  • Irreversible e.g. dyflos
132
Q

Effects of anticholinesterases can affect 3 main areas of body?

A
  • Autonomic cholinergic synapse
  • Neuromuscular junctions (NMJs)
  • Central nervous system (CNS)

IDM (8 decks)

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