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Physiology 1 > Lecture 4 cell signalling > Flashcards

Lecture 4 cell signalling Flashcards

1
Q

Why do cells signal?

A

Division, growth, differentiation, motility, metabolism, death, secretion and absorption

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2
Q

How do cells signal?

A

Cell-cell communication via chemical messengers

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3
Q

In what two ways do cells use chemical messengers?

A

Direct and indirect signalling

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4
Q

What are the two types of direct cell-cell communication?

A 
Gap junctions
Juxtracrine signalling (adjacent cells)
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5
Q

What are the 4 types of indirect cell signalling?

A

Autocrine, paracrine, endocrine and neuronal

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6
Q

What are the 4 types of cell signal?

A

Hormones
Growth factors
Inflammatory molecules
Neurotransmitters

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7
Q

Give two examples of inflammatory molecules.

A

Cytokines, prostaglandins

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8
Q

Name 4 neurotransmitters.

A

Acetylcholine, dopamine, GABA, noradrenaline (norepinephrine)

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9
Q

What are receptors?

A

Proteins that bind the signal molecule to induce a conformational change

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10
Q

What do intracellular signals cause within a cell?

A

Fast response: altered protein function

Slow response: altered gene expression

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11
Q

Name some second messenger molecules

A

Cyclic AMP
Nitric oxide
Cyclic GMP
Lipid metabolites

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12
Q

What are the 4 types of receptor?

A

Ion channels, G-protein linked receptors, enzymatic receptors and nuclear receptors

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13
Q

Give an example of an ion channel

A

Nicotinic acetylcholine receptor

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14
Q

Give examples of G-protein-coupled receptors

A

Adrenoceptors, glucagon receptor

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15
Q

Give an example of enzymatic receptors

A

Insulin and growth factor receptos

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16
Q

Name 3 examples of nuclear receptors.

A

Thyroxine, vitamin D and steroid hormone receptors

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17
Q

What is gap junction signalling?

A

Molecules are exchanged between cells via gap junctions

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18
Q

What proteins make up a gap junction?

A

2 connexons

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19
Q

What molecules make up a connexon?

A

6 connexin molecules

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20
Q

What name is given to a single connexon

A

A hemichannel

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21
Q

What is the ligand involved in juxtacrine signalling?

A

Plasma membrane of signalling cell A

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22
Q

What is the receptor involved in juxtacrine signalling?

A

Receptor in plasma membrane of adjacent cell B

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23
Q

Where is juxtacrine signalling important?

A

Cell migration

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24
Q

In most cases, where is the chemical messenger of indirect signalling secreted into?

A

Extracellular fluid/lymph/blood

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25
Q

What acts as the ligand during indirect signalling?

A

The signalling molecule

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26
Q

What does the signalling molecule elicit?

A

Cellular response in target cell

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27
Q

What is autocrine signalling?

A

Cell produces a local ligand that acts back on the receptor in the same cell

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28
Q

What does autocrine signalling allow the cell to do?

A

Sense extracellular environment (acts as biochemical radar)

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29
Q

What is paracrine signalling?

A

Cell produces a local ligand that acts on neighbouring cells

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30
Q

How do local ligands move during paracrine signalling?

A

Diffusion across short distances

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31
Q

Give an example of ligands moving via diffusion across short distances in paracrine signalling

A

Local recruitment of inflammatory cells by mast cells via histamine

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32
Q

What is endocrine signalling

A

Cell-cell communication over long distances

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33
Q

What are the signalling molecules in endocrine signalling called?

A

hormones

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34
Q

How are hormones transported?

A

In circulatory system via blood or lymph

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35
Q

What distances do messages travel in neural signalling?

A

Nerve impulses travel long distances and chemical messengers travel short distances

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36
Q

What other name is given to the nerve impulses travelling long distances in neural signalling?

A

Action potentials

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37
Q

What name is given to the travel of signalling molecules in neural signalling?

A

Synaptic transmission

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38
Q

What is the signalling cell in neural signalling?

A

The neuron cell

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39
Q

What type of signalling uses neurohormones as ligands?

A

Neuroendocrine signalling

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40
Q

How long does autocrine signalling take?

A

msec to sec

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41
Q

How long does paracrine signalling take?

A

msec to sec

42
Q

How long does endocrine signalling take?

A

sec to mins (can be hours to days)

43
Q

How long does neural signalling take?

A

msec only

44
Q

How do hydrophilic signals activate a response?

A

Activate plasma membrane receptors

45
Q

How are hydrophobic signals transported around the ECF/blood?

A

Globular transport proteins

46
Q

What type of receptors do hydrophobic signal molecules activate?

A

Intracellular (nuclear) receptors

47
Q

What classification of signalling molecules do all known hormones (and some neurotransmitters) fall into?

A

Peptides, amines, steroids

48
Q

What are the three other classes of signalling molecules, other than peptides, amines and steroids?

A

Lipids, purines, gases

49
Q

Are peptides, amines and steroids hydrophobic or hydrophilic?

A

Either

50
Q

Purines and gases are hydro___

A

philic

51
Q

What type of signalling molecule can single amino acids act as?

A

Neurotransmitters

52
Q

What amino acids can act as neurotransmitters?

A

Asp, Cys, Gly (Glu decarboxylated to form GABA)

53
Q

What are the two types of single amino acid neurotransmitters?

A

Excitory amino acids (EAA)

Inhibitory amino acids (IAA)

54
Q

Peptides (2-200aa) can act as what type of signalling molecules?

A

Neurotransmitters, hydrophilic hormones

55
Q

Where are peptides subject to post-translation modifications (e.g. glycosylation)?

A

Rough ER and golgi apparatus

56
Q

What signalling molecules are immediately released by exocytosis from their secretory vesicles?

A

Paracrine peptides- cytokines

57
Q

What signalling molecules go into storage before being released by exocytosis?

A

Most peptide hormones and neurotransmitters

58
Q

Are peptides soluble in ECF/blood/lymph?

A

Yes- don’t require carrier

59
Q

What type of hormones does the posterior pituitary release and what type of signalling is this?

A

Neuroendocrine signalling

Nonapeptide hormones

60
Q

Give two examples of nonapeptide hormones released by the posterior putuitary

A

Oxytocin (OT)

Arginine) Vasopressin (AVP

61
Q

On what receptors do peptides act?

A

Cell surface/transmembrane receptors

62
Q

How do peptides act on cell surface/transmembrane receptors?

A

Conformational change

63
Q

What is the result of a conformational change of a cell surface or transmembrane receptor in the presence of a peptide ligand?

A
  • Ion flux (iontropic receptor)

- Enzymes (metabotropic receptors)

64
Q

How are peptides degraded?

A

Proteases/peptidase

65
Q

What are the peptide half lifes?

A

Generally short:

  • Secs for simple peptides
  • Hours for glycoproteins
66
Q

What is the consequence of degrading peptide signalling molecules?

A

Continued action is dependent on continued synthesis

67
Q

What name is given to organic molecules containing amine (NH2-) usually derived from an aa?

A

Biogenic amines

68
Q

What biogenic amines are derived from tyrosine?

A

Catecholamines

69
Q

Give an example of catecholamines

A

Dopamine, noradrenaline and adrenaline

70
Q

Catecholamines are hydro___

A

philic

71
Q

What biogenic enzymes are derived from tyrosine derivatives?

A

Thyroid hormones

72
Q

Give an example of a thyroid hormone

A

Thyroxine

73
Q

Are thyroid hormones hydrophilic or hydrophobic?

A

Hydrophobic

74
Q

What biogenic amines are derived from tryptophan?

A

Indoleamines

75
Q

Give two examples of indoleamines

A

Serotonin and melatonin

76
Q

What biogenic amine is derived from histidine?

A

Histamine (hydrophilic)

77
Q

What biogenic amine is derived from choline (lipid)

A

Acetylcholine (hydrophilic)

78
Q

What are steroid hormones derived from?

A

Cholesterol

79
Q

How many carbons are there in cholesterol molecules?

A

27

80
Q

What class of hormones are steroid hormones?

A

Endocrine and paracrine hormones

81
Q

What do steroid hormones do in vertebrates vs invertebrates?

A

Vertebrates: sex steroids
Invertebrates: ecdysone

82
Q

What are steroid hormones implicated as?

A

Phermones for communication

83
Q

What are the 5 classes of steroid hormones?

A 
Progestins
Glucocorticoids
Mineralocorticoids
Androgens
Estrogens
84
Q

Name a progestin hormone and the number of carbons associated

A

Progesterone

21C

85
Q

Name a glucocorticoid and the number of carbon atoms

A

Cortisol

21C

86
Q

Name a mineralocorticoid and its number of carbons

A

Aldosterone, 21C

87
Q

Name an androgen and the number of carbons it has

A

Testosterone

19C

88
Q

Name an estrogen and the number of carbons it has

A

Estradiol

18C

89
Q

Where are steroid hormones synthesised?

A

Mitochondria and smooth ER

90
Q

What are the implications of steroid hormones being lipophilic?

A
  • Can’t be stored

- Synthesised immediately prior to secretion

91
Q

What two things do steroids bind?

A
  • Binding globulins

- Albumen

92
Q

What other hormones binds to carrier proteins, other than steroid hormones?

A

Thyroid hormones

Vitamin D/cholecalciferol

93
Q

By what laws do carrier proteins function by?

A

Laws of mass action and equilibrium

94
Q

What happens when free messenger enters the target cell and binds to the receptor?

A

Decreases concentration of free messenger, bound messenger dissociates from carrier protein

95
Q

What type of receptor do steroid hormones bind?

A

Nucelar receptors

96
Q

What are the two classes of nuclear receptor?

A

Class I nuclear receptor: cytosol

Class II nuclear receptor: nucleus

97
Q

What do nuclear receptors function as?

A

Ligand-dependent transcription facotr

98
Q

What do ligand-dependent transcription factors do?

A

Bind DNA to control access of RNA polymerase to the DNA template via histone acetylation

99
Q

What does controlling RNA polymerase access to DNA do?

A

Modulates transcription of genes in target cells

100
Q

How fast acting are nuclear receptors in ligand-dependent transcription factors?

A

Slow acting (hours to days)

101
Q

What is there increasing evidence for with steroid hormones?

A

Rapid effects via plasma membrane steroid receptors

Physiology 1 (9 decks)

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