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Cell physiology and pharmacology > Lecture 11- Biological signalling and receptors > Flashcards

Lecture 11- Biological signalling and receptors Flashcards

1
Q

define receptor

A

a molecule that recognises specifically a molecule (ligand) or family of molecules which in response to ligand binding brings about regulation of a cellular process

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2
Q

receptors in an unbound state

A

functionally silent

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3
Q

role of receptors

A
  • Neurotransmission - cellular deliver - control of gene expression - signalling by hormones - cell adhesion - modulation of the immune response - sorting of intracellular proteins - release off intracellular calcium stores
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4
Q

two main type of receptors

A

cell surface intracellular

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5
Q

cell surface receptors

A

tyrosine kinase GPCR Ligand gated Voltage gated

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6
Q

intracellular

A

nuclear e.g. steroids

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7
Q

ligand

A

any molecule which binds specifically to a receptor site

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8
Q

agonist

A

• May produce activation of a receptor

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9
Q

antagonist

A

• Oppose the action of agonist activation

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10
Q

signalling between cells via 92)

A

-secreted molecules - plasma membrane bound molecules (APCs)

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11
Q

types of signalling via secrete molecules

A

paracrine endocrine synaptic

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12
Q

paracrine

A

• Signalling molecule secreted into tissue and acts on adjacent cells • Local signal

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13
Q

endocrine

A

• If signalling molecule travels around the circulation to find target cell in different tissue • E.g. hormones

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14
Q

synaptic

A

• NT released in the junction b/w 2 nerve cells • E.g. NMJ

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15
Q

three main types of chemical signalling

A

• Local chemical mediators • Hormones • NT

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16
Q

difference between receptors and acceptors

A

Receptors are silent at rest, whilst acceptors operate in the absence of ligand/ Agonist binding to the receptor will stimulate biological response, whilst in acceptors, binding alone produces no response

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17
Q

affinity in enzymes

A

km

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18
Q

affinity in receptors

A

Kd

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19
Q

affinity of ligand binding at receptor site is generally much …… than binding of substrate and allosteric regulators to enzyme site

A

higher

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20
Q

receptors are classified according to

A

1) the agonist it recognises 2) affinity of a series of agonists 3) affinity of antagonists

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21
Q

affinity of a series of agonists e.g…

A

i. Nicotinic- higher affinity to nicotine ii. Muscarinic- higher affinity to muscarine

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22
Q

affinity of antagonists e.g..

A

• M1- antagonist= pirenzipine • M2- antagonist= gallamine • M3- antagonist= hexahydrosilodiphenol

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23
Q

the agonist it recognises e.g.

A

adrenoreceptors

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24
Q

types of receptors (4)

A
  1. Membrane-bound receptors with integral ion channel o Ligand-gated nAChR 2. Membrane-bound receptors with integral enzyme activity o GPCR- adrenaline 3. Membrane bound receptors which couple to effectors through transducing proteins o Tyrosine kinase- insulin 4. Intracellular receptors o Steroid receptors- oestrogen
25
Q

Membrane-bound receptors with integral ion channel e.g.

A

o Ligand-gated nAChR

26
Q

Membrane-bound receptors with integral enzyme activity

A

o GPCR- adrenaline

27
Q

Membrane bound receptors which couple to effectors through transducing proteins

A

o Tyrosine kinase- insulin

28
Q

Intracellular receptors

A

o Steroid receptors- oestrogen

29
Q

receptors on the cell surface for

A

hydrophilic signalling molecules

30
Q

receptors within the cell for

A

hydrophobic signalling molecules

31
Q

steroids can pass the lipid bilayer due to being

A

hydrophobic and small

32
Q

hydrophobic is used interchangeable with

A

lipophilic- will pass the membrane

33
Q

polar molecules

A

will not pass the membrane

34
Q

how are steroid transported

A

through the bloods on proteins such as albumin

35
Q

where are steroidal receptors

A

int he cytoplasm or nucleus

36
Q

steroids work to

A

activate or inhibit the expression of genes

37
Q

classical ligand gated ion channel

A
  • nAChR- gated Na+, K+, Ca2+ channel - Gaba receptor- gated chloride channel - Glycine receptor- gated chloride channel - Glutamate receptor- gated entry of Ca2+
38
Q

nicotinic acetylcholine receptor

A
  • Fastest mode of transport into the cell - Ligand-gated receptor (all have a pentameric structure)
39
Q

structure of nicotinic acetylcholine receptor

A

Pentameric- 2 subunits related to ACH binding- all subunits involved in resting pore

40
Q

outline how nicotinic acetylcholine receptor causes influx of sodium and depolarisation

A

1) ACh binds to the receptor 2) Causes the gate to open 3) Na+ can flood into cell and cause depolarisation of end plate

41
Q

non classical ligand gated ion channels

A
  • ATP-sensitive K+ channel - Ryanodine receptor (calcium)
42
Q

example of a membrane bound receptor with integral enzyme activity

A

signalling via Tyrosine Kinases

43
Q

tyrosine kinases receptors work as

A

dimers

44
Q

outline how TKs cause cellular signalling

A
  • Dimerization causes autophosphorylation of tyrosine residues on the inside of the channel—> 2nd messenger signalling - Receptors generally work via transducer proteins o Transducer phosphorylation by tyrosine residues o Transducer binds target enzyme and activates
45
Q

example of Tyrosine kinase receptros

A

growth factor receptors ANP receptors

46
Q

ANP receptors

A

linked directly to guanylyl cyclase

47
Q

growth factor receptors (TK)

A

linked directly to tyrosine kinase

48
Q

give example of ligand of growth facotor receptor ligands

A

insulin epidermal growth factor (EGF) platelet derived growth factor (PDGF)

49
Q

When the tyrosine residues are phosphorylated

A

enzymes (transducers) recongise the complex due to SH2 domain. - Example transducers: IRS-1, Grb2

50
Q

when insulin binds to its TK receptor

A
  • Insulin binds to the insulin binding domain on the extracellular region of the tyrosine kinase receptor - This causes a conformational change in the receptor- dimerization - Dimerization causes autophosphorylation of tyrosine kinase domain on the inner part of the receptor - Phosphorylated TKs attract transducers o Overall will cause increased transcription of DNA o Increased number of GLUT4 channels
51
Q

structure of insulin receptor

A

made up of alpha and beta change linked by disulphide bridge - 2 binding domains - 1 transmembrane domain - 2 tyrosine kinase domains

52
Q

Membrane bound receptors which couple to effectors through transducing proteins e.g.

A

G-protein couple receptors

53
Q

G-protein couple receptors are the

A

biggest class of receptors

54
Q

structure of GPCR

A
  • 7 transmembrane domain receptors - Coupled through GTP-binding regulatory protons (G-proteins) to enzymes or channels
55
Q

G protein is composed of

A

three subunits: ◦Alpha ◦Beta ◦Gama

56
Q

example of adrenaline binding to GPCR

A

• In resting state GDP is bound to the G-protein • Adrenaline comes along and binds causing a confirmation change in receptor • GDP is released from alpha subunit of G-protein • GTP is able to bind to the g-protein • G-protein dissociates • G-protein activates effector • Effector (AC) converts ATP to cAMP (Gs)

57
Q

how does the steroid receptor work

A

• Receptors held in silent state by inhibitory protein complex - blocks DNA binding site • When a steroid hormones binds the inhibitory protein is released and the DNA binding site is free

58
Q

responses to receptor activation can lead to both

A

cellular activation or inhibition depdneing on the type of receptoer activated

59
Q

amplification in cellular signalling

A

binding of a signal ligand to a receptor, can cause a huge reaction within a cell

e.g.

  • Activated G-protein (with GTP attached) activates effector enzyme ((AC)
  • AC causes ATP–> AMP
  • CAMP activates protein kinases
  • Protein kinase phosphorylates thousands of enzymes
  • Product of enzyme

Cell physiology and pharmacology (20 decks)

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