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1.1 POM Cells > Cell Signalling > Flashcards

Cell Signalling Flashcards

1
Q

Why do cells need to communicate? (4)

A
  1. Process information (from sensory stimuli)
  2. Self preservation eg. reflexes
  3. Voluntary movement
  4. Homeostasis
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2
Q

What are the 2 pathways of cell communication?

A
  1. Hormone
  2. Electrical impulses
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3
Q

What are the 4 different types of cell signalling?

A
  1. Endocrine
  2. Paracrine
  3. Membrane-attached protein
  4. Autocrine
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4
Q

What is endocrine signalling?

A

Hormone travels in blood to reach distant target cell

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5
Q

What is an example of endocrine signalling?

A

Hypoglycaemia glucagon action

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6
Q

How does hypoglycaemia control involve endocrine signalling? (3)

A
  1. Pancreas α-cells secrete glucagon
  2. Glucagon travels in blood
  3. Acts on liver —> glycogenolysis and gluconeogenesis
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7
Q

What is paracrine signalling?

A

Hormone acts on adjacent cell

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8
Q

What is an example of paracrine signalling?

A

Hyperglycaemia insulin action

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9
Q

How does hyperglycaemia control involve paracrine signalling? (2)

A
  1. β-cells detect increased blood glucose
  2. Insulin secreted —> acts on adjacent β-cells to inhibit glucagon secretion
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10
Q

What is membrane-attached protein signalling?

A

Interactions between plasma membrane proteins of different cells/particles

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11
Q

What is an example of membrane-attached protein signalling?

A

Cell-mediated response (APC and T-cell)

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12
Q

How does the cell-mediated immune response involve membrane-attached protein signalling?

A
  1. APC digests pathogen and expresses MHC II
  2. Th cell TCRs bind to MHC II
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13
Q

What is autocrine signalling?

A

Signalling molecule is acts on cell it comes from

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14
Q

What is an example of autocrine signalling?

A

T-cell IL-2

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15
Q

How does T-cell action involve autocrine signalling?

A
  1. Activated TCR initiates reaction cascade in T-cell
  2. Activated T-cell expresses IL-2 receptor on surface
  3. Activated T-cell secretes IL-2 —> binds to receptors on own cell
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16
Q

What are 3 steps of neurotransmission?

A
  1. Propagation on action potential
    - VGSCs open —> Na+ influx —> action potential
    - VGKCs open —> K+ influx —> repolarise
  2. Neurotransmitter release
    - Pre-s n VGCCs open —> Ca2+ influx —> vesicle exocytosis
  3. Activation of post-s n
    - Neurotransmitter diffuses across synapse —> binds to post-s n receptors
    - Different types of receptors present
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17
Q

What are the 4 types of receptors post-s ns can have?

A
  1. Ionotropic
  2. G-protein coupled
  3. Enzyme-linked
  4. Intracellular
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18
Q

What is the main principle behind ionotropic receptors?

A

Ligand binds —> opens ion permeable pore across membrane

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19
Q

What is the main principle behind G-coupled protein receptors?

A

Ligand binds —> activates intracellular G-protein

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20
Q

What is the main principle behind enzyme-linked receptors?

A

Ligand binds —> receptor clustering —> activates internal enzymes

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21
Q

What is the main principle behind intracellular receptors?

A

Membrane permeable to ligand —> passes through
—> binds to intracellular receptor

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22
Q

What are the 3 steps in the mechanism of ionotropic receptors?

A
  1. Ligand binds to receptor
  2. Channel protein shape change —> opens pore
  3. Ions move in/out depending on gradient
23
Q

What are are 2 examples of ionotropic receptors?

A
  1. Nicotinic ACh receptor
  2. GABA-A receptor
24
Q

What type of receptors are nicotinic ACh receptors and what is their function?

A

Ionotropic
- Binds to ACh
- Stimulates muscle contraction

25
Q

What are the 5 steps in the mechanism of G-protein coupled receptors?

A
  1. Ligand binds to GPCR
  2. GPCR changes conformation —> G-protein binds
  3. Stimulates GDP —> GTP (bound to Gα sub-unit)
  4. Stimulates G-protein dissociation —> Gα and Gβγ
  5. Gα and Gβγ bind to target protein
26
Q

What are the 3 steps of the mechanism of GPCR deactivation?

A
  1. GTPase causes GTP —> GDP (bound to Gα sub-unit)
  2. Gα sub-unit dissociates from target —> inactive
  3. GPCR not deactivated till ligand isn’t bound
27
Q

What is the shape of a GPCR?

A

Snakes crossing membrane 7 times (7-TM)

28
Q

What is the quaternary structure of G-proteins?

A

Heterotrimeric —> α, β, γ
- α associated with GDP/GTP
- β and γ always together

29
Q

What are the 3 types of G proteins?

A
  1. S
  2. I
  3. Q
30
Q

What do Gs protein-linked receptors do?

A

Stimulate adenylyl cyclase:
-ATP —> cAMP —> PKA

31
Q

What do Gi protein-linked receptors do?

A

Inhibit adenylyl cyclase
- less PKA

32
Q

What do Gq protein-linked receptors do?

A

Stimulate phospholipase (PLC)
-PIP2 —> IP3 —> Ca2+ release
—> DAG —> PKC

33
Q

What happens when Gs proteins stimulate adenylyl cyclase?

A
  1. ATP —> cAMP
  2. cAMP activates PKA (protein kinase A)
34
Q

What happens when G proteins inhibit adenylyl cyclase?

A

Decrease protein kinase A (PKA) levels

35
Q

What happens when Gq proteins stimulate phopholipase C?

A
  1. PIP2 —> IP3 + DAG
  2. IP3 stimulates Ca2+ release
    DAG activates protein kinase C
36
Q

What is an example of a Gs protein-linked receptor and what is its function?

A

β1-adrenergic receptor
- Adrenaline/NA binds —> inc heart rate

37
Q

What is an example of a Gi protein-linked receptor and what is its function?

A

M2-muscarinic receptor
- ACh binds —> dec heart rate

38
Q

What is an example of a Gq protein-linked receptor and what is its function?

A

AT-1 angiotensin receptor
- AT-1 binds —> vasoconstriction
- Hypertension drugs block AT-1 receptor

39
Q

What are the 5 steps in the mechanism of enzyme-linked receptors?

A
  1. Ligand binds —> receptors cluster
  2. Activates enzyme activity in cytoplasmic domain
  3. Enzymes phosphorylate receptor via signal protein binding
  4. Starts signal protein cascade
40
Q

Which type of receptor is involved in cell proliferation and why?

A

Enzyme-linked receptors
- Slowest

41
Q

Which type of receptor can be a target for cancer drugs and why?

A

Enzyme-linked receptors
- involved in cell proliferation

42
Q

How long does each type of receptor take to work?

A
  1. Ionotropic —> ms-s
  2. G-protein couples —> s-mins
  3. Enzyme-linked —> mins-hrs
  4. Intracellular —> hrs-days
43
Q

Which type of receptor is the fastest?

A

Ionotropic

44
Q

Which type of receptor is the slowest?

A

Intracellular

45
Q

What are 2 examples of enzyme-linked receptors?

A
  1. Insulin receptor
  2. ErbB receptor
46
Q

What are the 2 types of intracellular receptors?

A
  1. Type 1 —> cytoplasmic
  2. Type 2 —> nuclear
47
Q

What are the 5 steps in the mechanism of type 1 intracellular receptors?

A
  1. Hormone passes across membrane
  2. Hormone binds to receptor in cytoplasm
  3. Hsp (heat shock protein) dissociates
  4. 2 Hormone-bound receptors join —> homodimer
  5. Homodimer to nucleus —> binds to DNA
48
Q

What are the 2 steps in the mechanism of type 2 intracellular receptors?

A
  1. Hormone passes through membrane and cytoplasm
  2. Hormone binds to nuclear receptor —> regulates transcription
49
Q
A
49
Q

What is an example of a type 1 intracellular receptor?

A

Glucocorticoid receptor

50
Q

What is an example of a type 2 intracellular receptor?

A

Thyroid hormone receptor

51
Q

What are the ligands for and effects of glucocorticoid receptors?

A
  • Ligands —> cortisol, corticosterone
  • Effect —> dec immune response, inc gluconeogenesis
52
Q

What are the ligands for and effects of thyroid hormone receptors?

A
  • Ligands —> T3 (triiodothyronine), T4 (thyroxine)
  • Effect —> growth, development

1.1 POM Cells (15 decks)

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