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POM 2 Cell biology > 2.9 Cell Signaling > Flashcards

2.9 Cell Signaling Flashcards

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1
Q

What are the four reasons we need cell signalling?

A
  1. Process sensory stimuli
  2. Self preservation (e.g. spinal reflexes)
  3. Voluntary movement
  4. Homeostasis (e.g. thermoregulation, glucose homeostasis)
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2
Q

What is meant by self-preservation?

A

The activation of the reflex arc to protect ourself from danger

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3
Q

What are the two systems which provide the main lines of communication?

A

Nerve fibers of the central and peripheral nervous system

Blood vessels of the cardiovascular system

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4
Q

What line of communication is used for a rapid, instantaneous response?

A

The nerve fibres of the CNS and PNS

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5
Q

What line of communication is slower and more versatile?

A

The blood vessel system

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6
Q

What is meant by intercellular signalling?

A

Signalling between cells

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7
Q

What is meant by intracellular signalling?

A

Signalling within a cell

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8
Q

What are the four methods of signalling?

A
  1. Autocrine
  2. Endocrine
  3. Paracrine
  4. Communication between membrane attached proteins
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9
Q

What is meant by endocrine communication?

A

When the hormone travels in the blood vessel and acts on a distant target cell

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10
Q

How does glucagon act as an example of endocrine signalling?

A

Glucagon is released by the alpha cells of the Islets of Langerhans, and then transported in the blood to act on the liver

This stimulates gluconeogenesis and glycogenolysis

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11
Q

How does insulin provide an example of endocrine communication?

A

Insulin produced by the pancreas acts on muscle and adipose tissue

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12
Q

How does adrenaline provide an example of endocrine communication?

A

Produced by the adrenal glands and travels in the blood to act on many body systems like the lungs and trachea

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13
Q

What type of communication is shown in response to hypoglycaemia?

A

Endocrine

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14
Q

What types of communication is shown in response to hyperglycemia and why?

A

Paracrine – beta cells release insulin which inhibits glucagon secretion from adjacent alpha cells

Endocrine – reduces glycogenolysis and gluconeogenesis in liver

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15
Q

What is meant by paracrine communication?

A

When the hormone that is released acts on the adjacent cell

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16
Q

How does the pancreas show paracrine communication?

A

Insulin produced by the beta cells acts on the adjacent alpha cells inhibit glucagon production

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17
Q

Describe how nitric oxide acts in a paracrine manner

A

Nitric oxide is produced by endothelial cells in blood vessels and causes vasodilation

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18
Q

Describe how osteoclast activating factors work in a paracrine manner

A

They are produced by adjacent osteoblasts

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19
Q

What is meant by membrane attached protein comunication?

A

When plasma proteins in the membrane of two different cells interact

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20
Q

Describe an immunological example of membrane-attached protein communication

A

APC detects a bloodborne virus
APC digests the pathogen and expresses MHC II on surface
Circulating T cell interacts with MHC II via T cell receptors

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21
Q

Give 2 other examples of signalling between membrane attached proteins

A

HIV GP120 glycoprotein binds to CD4 receptors on T lymphocytes

Bacterial cell wall components bind toll-like receptors on haematopoietic cells

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22
Q

What is meant by autocrine communicaiton?

A

When a hormone acts on the same cell that produced it

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23
Q

How do T cells display autocrine forms of communication?

A

When T cells become activated they express IL-2 receptors and also release IL-2 which mediates cytokine release and binds to the receptor on the same cell

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24
Q

How does ACh display autocrine signalling?

A

ACh binds to presynaptic M2 muscarinic receptors

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25
Q

How do growth factors show autocrine communication?

A

Growth factors from tumour cells can bind to and act on tumour cells to cause mitogenesis

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26
Q

Describe how neurotransmission occurs?

A
  1. Acton potential arrives at the synapse due to an influx of sodium ions into the pre-synaptic bouton
  2. This triggers the opening of voltage gated calcium channels, allowing an influx of Ca2+ into the neurone
  3. Ca2+ binds to vesicles containing NT
  4. The NT vesicles then move to the cell membrane and are released into the synapse through exocytosis
  5. They then bind to receptors on the post-synaptic neurone
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27
Q

What are the four distinct categories of receptors which exist?

A
  1. Ligand gated ion channel receptors
  2. G protein coupled receptors
  3. Enzyme-linked receptors
  4. Intracellular receptors
28
Q

How do ligand-gated ion channel (ionotrophic) receptors work?

A

Ligand binds to receptor protein
Conformational change in the protein opens a pore
This allows the flow of ions in or out of the cell

29
Q

How is the direction of the movement of ions through ionotrophic receptors determined?

A

Through concentration gradients

30
Q

What is an example of an ionotrophic receptor?

A

Acetylcholine binds to nicotinic ACh receptors on skeletal muscle resulting in muscle contraction

31
Q

What is the ligand for NMDA receptors?

A

Glutamate

32
Q

What is the ligand for GABA alpha receptors?

A

GABA

33
Q

What are G-coupled receptors also known as and why?

A

7-transmembrane receptors as the channel protein crosses the membrane 7 times

34
Q

In resting state what does the G protein complex consist of?

A

Alpha subunit, beta-gamma subunit, and an associated GDP molecule

35
Q

Describe how G coupled receptors work?

A
  1. G protein complex binds to G coupled receptor which is embedded in the cell membrane
  2. The GDP is phosphorylated and swapped with GTP
  3. The G protein complex dissociates into alpha and beta-gamma subunits with alpha binding to a target protein
  4. GTP is dephosphorlyated to GDP, thus the alpha subunit dissociates from the target protein and binds beta-gamma again
36
Q

What is stimulated to convert ATP to cAMP?

A

AC - adenyl cyclase

37
Q

What is cAMP?

A

Cyclic adenosine monophosphate

38
Q

What does cAMP activate?

A

Protein kinase A

39
Q

Which G protein linked receptor activates adenylyl cyclase?

A

Gs protein linked receptor

40
Q

Which G protein linked receptor inactivates adenylyl cyclase?

A

Gi protein linked receptor

41
Q

What is an example of a G protein linked receptor which stimulates adenylyl cyclase?

A

Beta 1-adrenergic receptor

42
Q

What is an example of a G protein linked receptor which inacitaves adenylyl cyclase?

A

M2 muscarinic receptor

43
Q

What is the downstream effect of Gq protein linked receptors?

A

Activates AT-1 angiotensin receptor due to protein kinase C being activated

44
Q

How do enzyme linked receptors work?

A
  1. Ligand binds and receptors cluster
  2. Enzymes phosphorylate the receptor, causing binding of signalling proteins to the receptor’s cytoplasmic domain
  3. The signalling proteins recruit other ones, generating a signal in the cell
  4. Signal terminates when phosphatase dephosphorylates the receptor
45
Q

What enzyme is activated when insulin binds to the insulin receptor?

A

Tyrosine kinase

46
Q

What enzyme is activated when ANP and BNP bind to the NPR1 receptor?

A

Guanylyl cyclase

47
Q

What enzyme is activated when TGF beta binds to TGF B receptors?

A

Serine/threonine kinase

48
Q

What is the physiological effect of serine/threonine kinase activation?

A

Apoptosis

49
Q

What is the physiological effect of activation of tyrosine kinase?

A

Glucose uptake and lipid metabolism

50
Q

What is the physiological effect of activation of guanylyl cyclase?

A

Vasodilation and reduction in blood pressure

51
Q

Where are type 1 intracellular receptors located?

A

Within the cytosolic compartment

52
Q

Where are type 2 intracellular receptors located?

A

In the nucleus

53
Q

What chaperone molecules are type 1 intracellular receptors normally associated with?

A

Heat shock proteins

54
Q

How do type 1 intracellular receptors work?

A
  1. Hormone enters through membrane
  2. Binds to receptor, heat shock protein dissociates
  3. 2 hormone bound receptors form a homodimer
  4. Homodimer translocates to the nucleus and binds to DNA
55
Q

How do type 2 intracellular receptors work?

A

The hormone ligand binds straight to the DNA in the nucleus

56
Q

What is an example of a type 1 intracellular receptor?

A

Glucocorticoid receptor

57
Q

What ligands binds to the glucocorticoid receptor?

A

Cortisol and corticosterone

58
Q

Physiological effect of cortisol binding to glucocorticoid receptor?

A

Reduced immune response and increased gluconeogenesis

59
Q

What is an example of a type 2 intracellular receptor?

A

Thyroid hormone receptor

60
Q

What is the associated ligand for the thyroid hormone receptor?

A

Thyroxine and triiodothyronine

61
Q

With type II intracellular receptors, what causes the direct transcriptional regulation?

A

Activated hormone-receptor complex

62
Q

What is a homodimer?

A

When two identical hormone receptor complexes join

63
Q

Intracellular receptors are essentially what?

A

Transcription factors

64
Q

Why do steroid hormones extert their actions on intracellular receptors?

A

They are membrane permeable

65
Q

When the hormone binds to the receptor, what dissociates?

A

The heat shock protein

66
Q

What is a ligand?

A

A molecule that binds to a receptor to exert a specific effect

POM 2 Cell biology (15 decks)

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