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Molecular Cell Biology > Cell Signalling I > Flashcards

Cell Signalling I Flashcards

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1
Q

What are the mechanisms of intracellular communication?

A

Direct - cell to cell signalling

Indirect - Chemical messengers

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2
Q

What are examples of direct cell to cell signalling?

A

Gap junctions

Receptor-ligand signalling

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3
Q

What is cell signalling?

A

The transfer of information from one cell to another. Also called cell-cell signalling and intercellular communication

It controls the inner workings of organisms allowing them to respond, adapt and survive

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4
Q

Why is cell signalling important?

A

It is important for the understanding the functioning of a normal cell and the growth and activity of an aberrant cell

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5
Q

What happens when cell communication goes wrong and signal is lost?

A

This can lead to diseases such as Type I diabetes

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6
Q

What happens when cell communication goes wrong and signal does not reach its target?

A

Can lead to diseases such as multiple sclerosis

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7
Q

What happens when cell communication goes wrong and target ignores the signal?

A

Can lead to diseases such as Type II diabetes

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8
Q

What happens when cell communication goes wrong and too much signalling occurs?

A

Can result in Excitotoxicity

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9
Q

What happens when cell communication goes wrong and there are multiple breakdowns?

A

Can lead to cancer

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10
Q

What is the main principles of cell signalling?

A

Arrival of signal

Perception of the signal by receptors

Transmission of the signal by the receptor to the cell

Passing on the message-Signal transduction

The arrival of the message at the final destination

A response by the cells

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11
Q

What are the commonly seen changes in cell signalling? (1)

A

An alteration of the concentration of intracellular molecule such cAMP or cGMP

Changes in the activity of a protein- Enzymes

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12
Q

What are the commonly seen changes in cell signalling? (2)

A

Changes in the conformation of a protein

Changes in the location of a molecule

Changes in gene expression

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13
Q

What is a good signal?

A

A signal should be able to be made, mobilised and altered relatively quickly

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14
Q

How does direct signalling occur through gap junctions?

A

Composed of membrane proteins-Connexins

Link cytosol of two adjacent cells

Particles movement between cells acts as signal

Communication is direct

Common in smooth and cardiac muscle

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15
Q

How does direct signalling occur through surface markers?

A

Signal molecule remains bound to cell surface

Influences only cells that contact it

Important in development, immune response

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16
Q

How does indirect signalling occur through chemical signalling?

A

Messenger is produced by source cell

Messenger is transported to target

Target cell has receptors for messenger

Binding of messenger to receptor triggers a target cell response

Communication is indirect

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17
Q

What are the four forms of intracellular signalling?

A

Endocrine
Paracrine
Autocrine
Synaptic

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18
Q

What range of signalling is long range?

A

Electrical

Endocrine

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19
Q

What signalling is Short range?

A

paracrine

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20
Q

What range of signalling is autocrine and cell-cell contact?

A

a- same cell

c- neighbouring cells

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21
Q

How does electrical signalling occur?

A

Propagation of an electrical potential along a cell

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22
Q

How does Endocrine signalling occur?

A

Release and perception of hormones

23
Q

How does Paracrine signalling occur?

A

Release and perception of extracellular signals

24
Q

How does autocrine signalling occur?

A

Released signalling molecules act on the cell that release them

25
Q

How does cell to cell signalling occur?

A

Either by receptor mediated signalling or through gap junctions

26
Q

What components comprise signalling pathways?

A

Extracellular signals: Chemical messengers

Detection of extracellular signals : Receptors

Second messenger systems such cAMP and Inositol phosphates

Phosphorylation: Kinases and phosphatases

27
Q

What is a ligand?

A

a chemical messenger

28
Q

What is a source?

A

cells which produce the ligand

29
Q

What is a target?

A

has receptors for and responds to messenger

30
Q

What are chemical messengers?

A

Substances which have signaling functions

31
Q

What is the function of Paracrine?

A

Chemical that serves to signal a nearby cell

Example: Histamine, responsible for an inflammation response

32
Q

What is the function of Autocrine?

A

Chemical that signals the same cell that secreted it
Source and target are the same
Example: cytokines, growth factors

33
Q

What is the function of Neurotransmitters?

A

Messenger produced by neurons
Released into the ECF of synaptic cleft
Examples: Acetylcholine, glycine, serotonin

34
Q

What is the function of Hormone?

A

Messenger produced by endocrine cells
Secreted into blood via interstitial fluid
Examples: Insulin, estrogen, thyroxin

35
Q

What is a Lipophobic Ligand?

A 
Not lipid soluble; is water soluble
Does not easily cross cell membrane, which may require pumps or channels
Receptors on cell membrane
General action of target response
 - Enzyme activation
 - Membrane permeability changes
36
Q

What is a Lipophillic Ligand?

A

Lipid soluble; not water soluble
Easily crosses cell membrane
Receptor location within cell (intracellular location)
General action of target response is via gene activation

37
Q

What are the chemical properties of Amino Acids?

A

Lipophobic

Target cell receptors on cell membrane

Only four amino acids function as messengers, all as neurotransmitters

Examples: Glutamate, aspartate, glycine, GABA

38
Q

What are the chemical properties of Amines?

A

Amino acid-derived Messengers

Most are lipophobic, except thyroid hormones

Target receptors on cell membrane

Examples: 
Catecholamines; derived from tyrosine
Thyroid hormones; made from two tyrosine amino acids
Histamine; made from histidine
Serotonin; made from tryptophan
39
Q

What are the chemical properties of Peptides and Proteins?

A

Most abundant type of ligand

Lipophobic

Target receptors on cell membrane

Made of chains of amino acids

  • Peptide ligand (<50 amino acids)
  • Protein ligand (>50 amino acids)

Examples: Insulin, glucagon, Cytokines, growth factors

40
Q

What are the chemical properties of Steroid Ligands?

A

Lipophilic

Intracellular target receptors

Derived from cholesterol

All steroid ligands function as hormones

41
Q

What are the chemical properties of Eicosanoid Ligands?

A

Lipophilic

Intracellular target receptors

Derived from arachidonic acid, a cell membrane phospholipid

Paracrine signalling

42
Q

How are Lipophobic ligands synthesised and released?

A

Synthesis is independent of demand
Stored in vesicles of source until needed
Release by exocytosis
Release rate determined by exocytosis

43
Q

How are Lipophilic ligands synthesised and released?

A

Synthesised on demand
Immediate release from source
Release rate depends on synthesis

44
Q

How are Amino Acids synthesised and released? (1)

A

Produced in cytosol of source

Stored in vesicles of source

Release is by exocytosis

The amine produced is dependent upon enzymes of target

45
Q

How are Amino Acids synthesised and released? (2)

A

Glutamate and aspartate made from glucose

Glycine made from 3-phosphoglycerate

GABA from glutamate

46
Q

How are Amines synthesised and released?

A

Synthesized within neuron (source)

Stored in vesicle until needed

Released by exocytosis

47
Q

How are Peptides and Proteins synthesised and released?

A

Formed by cleaving larger proteins
Stored in secretory vesicles
Released by exocytosis
General terminology

48
Q

How are Steroids synthesised and released?

A

Synthesized on demand

Derived from cholesterol molecule

All steroid ligands are similar

49
Q

How are Eicosanoids synthesised and released?

A

Derived from arachidonic acid
Synthesized on demand

Two major synthetic pathways

  • Cyclooxygenase pathway
  • Lipoxygenase pathway
50
Q

What happens when ligands diffuse?

A

Diffusion through interstitial fluid
Source and target are close
Ligand is quickly degraded
Examples: Paracrines, autocrines, neurotransmitters, and most cytokines

51
Q

What happens in blood Bourne transport with ligands?

A

Source and target at distance
Lipophobic ligands dissolve in plasma
Lipophilic ligands bind to carrier protein (ex. Steroids and thyroid hormones)
Examples: Hormones, neurohormones, and some cytokines

52
Q

What happens to messengers dissolved in plasma?

A

Have relative short half-life

Example: Half-life insulin is <10 min

53
Q

What happens when messengers are bound to plasma protein?

A

Have relative long half-life

Example: Half-life of cortisol = 90 min

Molecular Cell Biology (18 decks)

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