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BIOC192 2024 > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

What is signal transduction?

A

When an activated receptor starts a chain of events where messages are passed on through the cell to create a cellular response

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2
Q

What does signal transduction often provide?

A

Opportunities for coordination and regulation of the cellular response

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3
Q

What are the two mechanisms for signal transduction?

A

Second messengers and phosphorylation

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4
Q

What is the second messenger pathway often used by?

A

The G protein-coupled pathway

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5
Q

What are the second messengers used by GPCRs?

A

cAMP, cGMP, Calcium ion, inositol 1,4,5-triphosphate, diacylglycerol

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6
Q

What is the GPCR pathway of second messangers?

A

Intracellular molecules that change in concentration in response to receptor activation, this transmits signals from receptor to molecules as they are not attached to the membrane

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7
Q

What do phosphorylation and dephosphorylation events do?

A

Turn protein activity on and off as required

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8
Q

What is phosphorylation?

A

When the protein kinase transfers phosphates from ATP to protein

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9
Q

What is dephosphorylation?

A

When the protein phosphatase rapidly removes the phosphates from proteins to control signal transduction

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10
Q

What does signal transduction using protein kinase create?

A

A phosphorylation cascade

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11
Q

What are some mechanisms of signal transduction to regulate cellular activity?

A

Ligand dissociation, internalisation, phosphatase

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12
Q

What is internalisation?

A

The receptor is removed from the cell surface through endocytosis so it can no longer respond to a ligand

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13
Q

What is GPCRs?

A

The use of G proteins to start signal transduction, GPCR activates G protein which further communicates with other proteins in the cell

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14
Q

What are the two types of G protein?

A

G-alpha-s and G-alpha-I

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15
Q

What is G-alpha-s

A

Stimulatory G protein, which activates an enzyme called adenylate cyclase

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16
Q

What is the G protein made up of?

A

1x alpha, beta and gamma subunits

17
Q

What is G-alpha-I

A

Inhibitory G protein, which decreases the activity of adenylate cyclase

18
Q

What is the process of signal transduction for Gs-coupled GPCR?

A

Agonist ligand binds to GPCR which activates G-alpha-s protein to activate adenylate cyclase to increase the levels of cAMP and simulate the protein kinase A

19
Q

What is the process of signal transduction for Gs-coupled GPCR with the glucagon receptor?

A

Receptor activation from glucagon from the liver cells causes G protein activation and further signal transduction events leading to glycogen breakdown

20
Q

What is the process of signal transduction for Gs-coupled GPCR with the GLP-1 receptor?

A

Receptor activation from GLP-1 from the gut cells causes G protein activation and further signal transduction events leading to insulin secretion

21
Q

What is a RTKs?

A

Receptor tyrosin-kinase, a membrane-spanning dimer which undergoes a conformational change leading to a phosphorylation cascade

22
Q

What do RTKs use?

A

Phosphorylation of adaptor proteins to start signal transduction

23
Q

What are adaptor proteins?

A

Proteins that contain a variety of protein-binding modules that link protein-binding partners together

24
Q

How do adaptor proteins work?

A

By communicating with other proteins in the cell

25
Q

How does insulin receptor signal transduction work in muscle and adipose cells?

A

Receptor activation causes phosphorylation of an adaptor protein and further signal transduction events leading to GLUT-4 translocation

26
Q

What type of ligand is insulin?

A

Peptide ligand

27
Q

How does insulin receptor signal transduction work in liver cells?

A

Receptor activation causes phosphorylation of an adaptor protein and further signal transduction events leading to glycogen synthesis

28
Q

How do ligand gated ion channels work?

A

Agonist ligand binding causes a conformational change allowing ions to flow directly through the channel to produce effects. These are much faster as they don’t need sequential events

29
Q

How are responses controlled in signal transduction?

A

Based on where the receptors are expresses

30
Q

Is a cell specific to only one type of receptor?

A

No

31
Q

How do the same ligand/receptor pairings have different effects in different cells?

A

They use a different combination of relay modules

32
Q

What is cross-talking?

A

The communication pathway to help the cell coordinate signals from incoming ligands

BIOC192 2024 (25 decks)

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