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physiology > cell signalling > Flashcards

cell signalling Flashcards

1
Q

are membrane receptors most hydrophilic/phobic

A

hydrophilic

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2
Q

what does signal transduction pathways do

A

form a cascade

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3
Q

3 methods of cell communication

A

gap junctions, contact-dependent signals, diffusible chemical signals

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4
Q

method of cell communication

A

GP: direct cytoplasmic connections

Contact: interaction between membrane

diffusible: Autocrine signals act on same cell that secreted them, Paracrine signals are secreted by one cell and diffuse to adjacent cells

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5
Q

describe the paracrine and autocrine signalling process

A

derived from individual cells , act locally, diffuse through interstitial fluid

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5
Q

3 types of diffusible chemical signalling and the difference between them

A

Paracrine: Paracrine agent targets from local cell to local target cell
Autocrine: Autocrine agent targets local cell
Endocrine: from local cell to hormones to remote target cell

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6
Q

what happens to the signalling molecule in paracrine and autocrine signalling

A

either enzymatically destroyed or taken up by local
target cells → minimal entry into bloodstream

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7
Q

can Paracrine secretions act as autocrine

A

yes, e.g. act back on the secretory
cell

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8
Q

examples of paracrine and autocrine signalling

A

Metabolic hyperaemia
Platelet plug formation

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9
Q

describe Metabolic hyperaemia

A

Endothelium secretes
vasodilators (e.g. nitric
oxide) in response to
increased metabolism

Dilation of local
arterioles
↑ local blood flow

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10
Q

describe Platelet plug formation

A

Activated platelets
release agonists (e.g.
ADP, thromboxane A2)
Paracrine and
autocrine
Recruits more platelets
and amplifies platelet
activation

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11
Q

describe Endocrine signalling process

A

Hormones synthesised and secreted by
endocrine cells (glands) → extracellular fluid
→ blood → distributed throughout body i.e.
distant targets

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12
Q

how is the secretion triggered during endocrine signalling

A

a variety of signals:
* Changing levels of blood constituent
* Regulated by blood levels of another
hormone
* Regulated by activity of nerves

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13
Q

conditions needed for cells to respond to endocrine signalling to happen

A

Only cells with specific receptor for
specific hormone can respond

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14
Q

why must Receptors must bind hormones very
effectively

A

they must have a high
affinity for the specific hormone because of dilution in bloodstream,
[hormone]blood are very low (10-9
mol/l)

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15
Q

how big is the synaptic gap and how fast do signals get transmitted

A

Signals transmitted within milliseconds

~20 nm gap

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16
Q

what do electrical signals in nerves cause

A

Electrical signals (action potentials) in nerve
cause release of chemical (neurotransmitter) at
synapse → target cell

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17
Q

Name 2 types of neuronal signalling

A

neurotransmitter e.g. Ach, GABA

neurohormones e.g. adrenaline/noradrenaline

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18
Q

define signal transduction

A

converts one form of signal into a different form
e.g. signal molecules –> response

19
Q

what are the different types of cell membrane receptors

A

receptor channels, G protein coupled, receptor enzymes, integrin

19
Q

describe intracellular receptors, what type of molecules binds to it

A

Some signalling molecules are lipid soluble
* Move through the plasma membrane by simple diffusion
* These therefore bind to intracellular receptors in the cytosol (e.g. nitric
oxide) or in the nucleus (e.g. oestrogen

20
Q

what are receptor-enzymes also known as and give an example

A

enzyme-linked
receptors
* Receptors with intrinsic enzyme activity e.g. insulin receptors
* Bound to an enzyme e.g. cytokine receptors

20
Q

what are integrin receptors

A

Receptors that interact with the cytoskeleton
involved in:
* Cell movement
* Cell adhesion
* Platelet aggregation

20
Q

what are the different types of receptors

A

cell membrane receptors, intracellular, sensory

20
Q

what types of molecules binds to cell surface receptors

A

Hydrophilic signalling molecules bind to receptors on the cell surface

21
Q

what are receptor channels also known as and provide an example

A

ionic receptors
e.g. nicotinic acetylcholine receptors

21
Q

what are G protein coupled receptors also known as and give an example

A

metabotropic
receptors
e.g. adrenergic receptors

21
Q

what is the simplest and quickest receptor pathway

A

ionotropic receptors

21
Q

provide the process to which ionotropic receptors function

A

Binding of agonist to receptor → channel opening → change in
membrane potential

22
Q

what is the largest family of receptors

A

G protein-coupled receptors

23
Q

what is G- protein - coupled receptor bound to

A

intracellular GTP-binding regulatory
protein (G protein

24
Q

how many subunits does GPCRs have

A

G proteins have α, β and γ subunits (heterotrimeric)

25
Q

what happens to a GPCR when the signalling molecule binds

A

he GPCR exchanges
exchange guanosine
diphosphate (GDP) for guanosine triphosphate (GTP)
G protein disassociates from the receptor into α and βγ subunits
* Subunits can now interact with ion channels, 2nd
messengers

26
Q

example of GPCR

A

opening of ligand-gated K+ channels
leading to hyperpolarisation

27
Q

talk through the 5 steps of the GPCR-adenylyl cyclase pathway

A
  • G protein activates adenylyl cyclase
  • Adenylyl cyclase converts ATP to cyclic AMP and pyrophosphate
  • 2nd messenger cAMP activates protein kinase A
  • Protein kinase A phosphorylates target proteins and changes their
    activity
28
Q

how much is the amplification from the GPCR-adenylyl cyclase pathway

A

1 signalling molecule
→ 102 cAMP → 104 phosphorylated protein → 106 products

29
Q

describe the GPCR-phospholipase C pathway

A

G protein activates phospholipase C (PLC)
* PLC converts the membrane phospholipid phosphatidylinositol
bisphosphate (PIP2) into 2nd messengers:
* Diacylglycerol (DAG)
* Inositol trisphosphate (IP3)
* DAG activates protein kinase C
* IP3 releases Ca2+ from stores in the endoplasmic reticulum which also
activates protein kinase C
* Protein kinase C phosphorylates target proteins and changes their
activity

30
Q

how to differentiate between adenylyl cyclase and phospholipase C pathway

A

A denylyl cyclase → A TP → c A MP → protein kinase A
Phospholipase C → DAG → protein kinase C
IP3 → Ca2+
all A go together and all C

31
Q

what are receptors with intrinsic enzyme activity

A

protein kinases

32
Q

describe the enzyme receptor pathway

A

Binding of signalling molecule receptor → conformational change → enzyme activation → autophosphorylation →
phosphorylation (activation) of other proteins (e.g. enzymes)
* e.g. tyrosine kinase receptors

33
Q

name two molecules that use intracellular receptors

A

steroid hormones and NO

34
Q

when do steroid hormones is used in intracellular receptor signalling

A

Receptor is often a transcription factor that regulates transcription
in the nucleus

35
Q

describe how NO is used in intracellular receptor signalling

A
  • Binds to soluble guanylyl cyclase in the cytosol
  • Generates cGMP as 2nd messenger that regulates cell activity
36
Q

name a secondary messenger

A

Calcium

37
Q

name the sources of calcium

A
  • Release from internal stores via IP3- or Ca2+-stimulated release Ca2+ from endoplasmic reticulum
  • Extracellular via Ca2+ channels
38
Q

name the effects of calcium

A
  • Directly affects target protein (e.g. PKC)
  • Binds to calmodulin which affects protein (e.g. Ca2+-
    calmodulin dependent kinase - CamKinase)
  • Works via some other Ca2+ binding protein (e.g. troponin)
39
Q

summarise Ionotropic receptors, G protein-coupled receptors, GPCR signalling pathways, Ca2+

A
  • Ionotropic receptors are the simplest receptors and signalling through these is
    rapid
  • G protein-coupled receptors (GPCRs) are more complex
  • Know your GPCR signalling pathways!
  • Ca2+ is an important intracellular messenger

physiology (10 decks)

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