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POM 1a - Molecular Biology Of The Cell > Cell Signaling > Flashcards

Cell Signaling Flashcards

1
Q

Why do cells need to communicate?

A

Process information

Self preservation

Voluntary movement

Homeostasis

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2
Q

What are the 4 types of signalling?

A

Endocrine

Paracrine

Membrane attached proteins

Autocrine

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3
Q

What is endocrine communication?

A

Hormone travels within blood vessels to act on a distant target cell

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4
Q

Example of endocrine communication.

A

Hypoglycaemia

  • glucagon secreted by alpha cells of Islets of Langerhans
  • travels out of pancreas in blood vessels
  • stimulates glycogenolysis and gluconeogenisis w/in liver
    —> increasing blood glucose levels
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5
Q

What is paracrine communication?

A

Hormone acts on adjacent cell

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6
Q

Example of paracrine communication.

A

Hyperglycaemia

  • increased blood glucose - insulin secreted by beta-cells in Islets of Langerhans
  • insulin has paracrine effects —> inhibiting glucagon secretion
  • also has endocrine effects on the liver
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7
Q

What is membrane attached protein signalling?

A

Plasma membrane proteins on adjacent cells interacting

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8
Q

Example of membrane attached protein signalling

A

Blood borne virus —> detected in blood by antigen presenting cell

APC digests pathogen —> express major histo-compatibility class II molecules on surface

Circulating T-lymphocyte engages with MHC molecule through T-cell receptor interaction

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9
Q

What is autocrine communication?

A

Signalling molecule acts on the same cell

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10
Q

Example of autocrine signalling

A

Activates TCR will initiate a cascade o reaction within T-cell

Activated T-cell expresses interleukin-2 receptor on surface

Activated T-lymphocyte also secretes IL-2 which:
—> binds to IL-2 receptor on the same cell
—> binds to IL-2 receptor on adjacent activated T-cell

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11
Q

Process of neurotransmission.

A
  1. Propagation of the action potential
  2. Neurotransmitter release from vesicle
  3. Activation of postsynaptic receptors
  4. Activation of postsynaptic receptors
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12
Q

What are the 4 types of receptors?

A

Ionotropic

G-protein coupled

Enzyme-linked

Intracellular

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13
Q

What is an ionotropic receptor

A

Ligand binding —> opens ion permeable pore traversing the membrane

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14
Q

Events in an ionotropic receptor.

A

Ligand binds to the receptor protein

Change in conformation of channel protein —> opens pore

Pore allow soins to move in our out of cell

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15
Q

Ionotropic receptor example

A

Nicotinic Acetylcholine
Ligand: ACh
Location: skeletal muscle
Physiological effect: muscle contraction

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16
Q

What is a G-protein coupled receptor?

A

Ligand binding —> activates intracellular G-protein

17
Q

Events in a G-protein coupled receptor

A

7-TM receptor & heterotrimeric G-protein are inactive

Ligand binding —> changes conformation of receptor

Unassociated G-protein binds to the receptor —> GDP is exchanged for GTP

G-protein dissociates into two active components:
—> alpha - subunit
—> beta gamma - subunit
bind to their target proteins

Internal GTPase activity on alpha - subunit dephosphorylates GTP —> GDP

Alpha - subunit dissociates from target protein —> inactive again

Receptor remains active as long as ligand is bound and can activate further heterotrimeric G-proteins

18
Q

G-protein coupled receptor example

A

Gs protein linked receptor
—> stimulates adenylyl cyclase
—> beta-adrenergic receptor

Gi protein linked receptor
—> inhibits adenylyl cyclase
—> M2-muscarinic receptor

Gq protein linked receptor
—> stimulates phospholipase C
—> AT-1 angiotensin receptor

19
Q

What is an enzyme linked receptor?

A

Ligand binding —> receptor clustering —> activates internal enzymes

20
Q

Events of an enzyme-linked receptor

A

Ligand binding

Receptor clustering activates enzyme activity w/in cytoplasmic domain

Enzymes phosphorylate receptor

Phosphorylation —> binding of signalling proteins to cytoplasmic domain

These signalling proteins —> recruit other signalling proteins —> signal generated in cell

21
Q

Examples of enzyme-linked receptor

A

Insulin receptor

22
Q

What is an intracellular receptor?

A

Membrane permeable ligand binds to receptor inside cell

23
Q

Events in an intracellular receptor

A

Type 1 - Cytoplasmic

Located within the cytosolic compartment

Associated with chaperone molecules (heat
shock proteins, hsp)

Hormone binds to receptor ® hsp dissociates

2 hormone bound receptors form a
homodimer.

The homodimer translocates to the nucleus —> binds to DNA

Type 2 - Nuclear

Located within the nucleus

Binding of hormone ligand —> transcriptional regulation

24
Q

Example of intracellular receptors

A

Type 1: glucocorticoid receptor
Ligand: cortisol, corticosterone
Physiological effect: lower immune response, more gluconeogenisis

Type 2: thyroid hormone receptor
Ligand: thyroxine (T4), triiodothyronine (T3)
Physiological effect: growth and development

POM 1a - Molecular Biology Of The Cell (18 decks)

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