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POM CELLS > Cell Signalling > Flashcards

Cell Signalling Flashcards

1
Q

What are the four reasons we need cell signalling?

A
  1. To process information
  2. For self preservation
  3. For voluntary movement
  4. For 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 intercellular 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, to stimulate glyconeogenesis and glycogenolysis to make more glycogen and glucose

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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 type of communication is shown in response to hyperglycemia? and why

A

Paracrine and Endocrine - when blood glucose levels are too high, insulin is released which inhibits the secretion of glucagon from the alpha islet cells
Endocrine effects on the liver ie reduced glycogenolysis

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15
Q

What is meant by paracrine communication?

A

When the home 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 Alpha cells of the islet of langerhans to inhibit glucagon production

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17
Q

Describe how nitric oxide acts in a paracrine manner

A

Nitric Oxide produced by the endothelium in blood vessels, acts on the smooth muscle to vasodilate the vessels

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18
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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19
Q

Describe an immunological example of membrane-attached protein communication

A

An APC detects blood borne virus
Digests it and presents its antigens on MHC
A circulating T cell then interacts with the MHC through T cell receptors

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20
Q

What is meant by autocrine communicaiton?

A

When a hormone acts on the same cell that produced it

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21
Q

How do T cells display autocrine forms of communication?

A

When T cells become activated they express IL-2 receptors, as well as release IL-2 which mediates cytokine release

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22
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 n the post-synaptic neurone
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23
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
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24
Q

How do ionotrophic receptors work?

A

When an appropriate ligand binds to the ligand-binding domain on the external surface of the protein the pore opens due to a conformational change, allowing ions to move in or out

25
Q

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

A

Through concentration gradients

26
Q

What is an example of an ionotrophic receptor?

A

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

27
Q

What is the ligand for NMDA receptors?

A

Glutamate

28
Q

What is the ligand for GABA alpha receptors?

A

GABA

29
Q

What are G-coupled receptors also known as?

A

7-TRANSMEMBRANE RECEPTORS

30
Q

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

A

The Ga subunit, a GBγ subunit and an associated GDP molecule

31
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 two complexes - the Beta γ subunit and the Alpha subunit, each bind to their respective target proteins
  4. GTP is dephosphorlyated to GDP, causing the alpha subunit to dissociate from the target protein (becomes inactive again)
32
Q

What is stimulated to convert ATP to cAMP?

A

AC - Adenylyl cyclase

33
Q

What is cAMP?

A

Cyclic Adenosine monophosphate

34
Q

What does cAMP activate?

A

Protein kinase A

35
Q

Which g protein linked receptor activates AC?

A

Gs protein linked receptor

36
Q

Which g protein linked receptor inactivates AC?

A

Gi protein linked receptor

37
Q

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

A

B1 - adrenergic receptor

38
Q

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

A

M2 - muscarinic receptor

39
Q

What is the downstream effect of Gq protein?

A

Activates AT-1 angiotensin receptor due to Phospholipase C being activated

40
Q

How do enzyme linked receptors work?

A
  1. Ligand binds to receptor
  2. This results in clustering
  3. The clustering activates enzyme activity
  4. The enzymes which are activated then phosphorylate the receptor which leads to the binding of signalling proteins in the cytoplasmic domain
  5. These signalling proteins recruit other signalling proteins and a signal is generated within the cell.
  6. The signal is terminated when a phosphatase dephosphorylates the receptor.
41
Q

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

A

Tyrosine kinase

42
Q

What is the physiological effect of activation of Tyrosine kinase?

A

Glucose uptake and lipid metabolism

43
Q

Where are type 1 intracellular receptors located?

A

Within the cytosolic compartment

44
Q

Where are type 2 intracellular receptors located?

A

In the nucleus

45
Q

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

A

heat shock proteins (hsp)

46
Q

How do type 1 intracellular receptors work?

A
  1. Hormone enters through membrane
  2. Binds to receptor, HSP Dissociates
  3. 2 hormone bound receptors form a homodimer
  4. Homodimer translocates to the nucleus and binds to DNA
47
Q

How do type 2 intracellular receptors work?

A

The hormone ligand binds straight to the DNA in the nucleus

48
Q

What is an example of a type 1 intracellular receptor?

A

Glucocorticoid receptor

49
Q

What ligands binds to the glucocorticoid receptor?

A

Cortisol and corticosterone

50
Q

Physiological effect of cortisol binding to glucocorticoid receptor?

A

Reduced immune response and increased gluconeogenesis

51
Q

What is an example of a type 2 intracellular receptor?

A

Thyroid hormone receptor

52
Q

What is the associated ligand for the thyroid hormone receptor?

A

Thyroxine and triiodothyronine

53
Q

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

A

Activated hormone-receptor complex

54
Q

What is a homodimer?

A

When two identical hormone receptor complexes join

55
Q

Intracellular receptors are essentially what?

A

Transcription factors

56
Q

Why do steroid hormones exert their actions on intracellular receptors?

A

They are membrane permeable

57
Q

When the hormone binds to the receptor, what dissociates?

A

The heat shock protein

58
Q

What is a ligand?

A

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

POM CELLS (15 decks)

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