Cell signalling Flashcards

1
Q

What is the purpose of cell communication?

A

Homeostasis
Self preservation
Processing information
Voluntary movement

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2
Q

What is endocrine communication?

A

Endocrine glands consider the direct secretion and release of hormones int the blood

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3
Q

What is the process of glucagon secretion?

A

Glucagon is secreted by alpha-cells of islets of Langerhans
Traverses out of the pancreas and released into blood vessels
Binds to glucagon receptor (G-coupled receptor)
Secondary messenger system to increase hepatic glucose output

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4
Q

What type of receptor are glucagon receptors?

A

G-coupled receptors

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5
Q

What are the examples of endocrine communciation?

A

Hormones travel within vasculature to bind onto distant target cell receptors
Insulin (Produced in pancreas, acts on muscle, liver and adipose)
Adrenaline produced by adrenal medulla

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6
Q

What is paracrine communication?

A

Denotes the secretion of hormones diffusion from the source to localized target cells

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7
Q

Describe the paracrine communication involved in hyperglycemia:

A

Insulin secretion by B-cells in the islets of Langerhans

Inhibits glucagon secretion

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8
Q

What is paracrine signalling?

A

Hormones act on adjacent cell

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9
Q

What are the examples of paracrine communication?

A
Osteoclast activating factor produced by adjacent osteoblasts
Nitric oxide (mediates vasodilation) produced by endothelial cells
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10
Q

How do antigen presenting cells present antigens?

A

Antigens undergo internalization and fragmentation and the endoplasmic reticulum, proteases cleave antigen into antigenic fragments, associated to MHC molecules on cell surface membranes

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11
Q

What receptors bind to MHC Class 2 molecules?

A

TCRs

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12
Q

The interaction between T-cell receptors and MHC-II is an example of what?

A

Signalling between membrane attached proteins

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13
Q

What is autocrine signaling?

A

Communication with self

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14
Q

What is the examples exhibited by T-cells during autocrine cell signaling?

A

Secretion of IL-2 from activated T-Cell
Binds onto cell surface membrane receptor
IL-2 promotes differentiation into T-effector and memory cells

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15
Q

What are ionotropic receptors?

A

Ligand binding –> opens ion permeable pore traversing the membrane

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16
Q

What is the structure of ionotropic receptors?

A

Transmembrane protein consists of a central pore within quaternary structure: Ligand-binding domain results in pore opening

17
Q

Describe the sequence events upon ligand binding on ionotropic receptors?

A

Ligand binds onto receptor protein
Change in conformation of channel proteins –> Opening of a pore
Pore facilitates the movement of ions according to concentration gradient

18
Q

What are the examples of ionotropic receptors?

A

Ligand: ACh
Location: Skeletal muscle
Physiological effect: Muscle contraction

19
Q

What are the sequence events following binding of G-protein coupled receptor?

A

7-TM receptor & heterotrimeric G-protein are inactive
Ligand binding –> conformational change of receptor
Unassociated g-protein binds to the receptor –> Bound GDP molecule is phosphorylated to GTP
G-protein dissociates into two components (Alpha, and g-beta/gamma)
Binding to target proteins

Internal GTPase activity on alpha subunit dephosphorylates GTP to GDP
Heretrotimeric G dissociates upon ligand deactiviation

20
Q

What are the two components in which G-protein splits into?

A

Alpha subunit

Beta & Gamma subunits

21
Q

What is associated with the alpha subunit?

A

GTP and GTPase

22
Q

What is the name for the transmembrane protein involved in G-protein coupled receptors?

A

7-tm

23
Q

What are the examples of a Gs linked receptor?

A

B1- adrenergic receptor

Converts ATP to cAMP via adenyl cyclase activity, activates protein Kinase A

24
Q

What is the example of a Gi protein-linked receptor?

A

Inhibits adenyl cyclase, reduction in cAMP and PKA

M2 muscarinic receptor on heart

25
Q

What is the example of a Gq-protein linked receptor?

A

AT-1 antgiotensin receptor

26
Q

What is the function of phospholipase c?

A

Converts PIP2 to IP3 and DAG

27
Q

What is IP3 in regards to phospholipase C?

A

Secondary messenger

28
Q

What does IP3 stimulate?

A

Calcium release

29
Q

What are enzyme-linked receptors?

A

Ligand binding –> receptor clustering activates enzyme activity with the cytoplasmic domain
Enzyme phosphorylates receptor
Phosphorylation of receptor leads to binding of signalling proteins to cytoplasmic domain
Signalling proteins recruit other signalling proteins
Signal terminates when a phosphatase dephosphorylates the receptor

30
Q

How is the signal terminated in enzyme-linked receptor signaling?

A

Phosphatase enzyme dephosphorylates receptor

31
Q

What are type-1 intracellular receptors?

A

Cytoplasmic
Located within the cytosolic compartment associated with chaperone molecules
Chaperone molecules involved in conformational folding
Hormone complex bind to receptor (heat shock proteins dissociate)
Behave as transcriptional factor upon binding to promoter region

32
Q

What are chaperone molecules?

A

Heat shock proteins associated with steroid hormones

Chaperone molecules assist with conformational change of hormone

33
Q

Which type of hormone acts on intracellular receptors?

A

Steroid hormones are membrane-permeable

34
Q

What are the examples of steroid hormones?

A

Cortisol, and corticosteroids

35
Q

what are type-2 intracellular receptors?

A

Nuclear, hormone ligand forms complex within the nucleus, binding to the transcriptional region.