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MCB2050 Part 1 > Signal Transduction and G Protein-Coupled Reactions > Flashcards

Signal Transduction and G Protein-Coupled Reactions Flashcards

1
Q

How do hydrophobic hormones diffuse through the cell?

A

Through the cell membrane and activate cytosolic receptors.

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2
Q

How do hydrophobic hormones diffuse through the cell.

A

They bind to plasma membrane receptors and activate signal transduction pathways.

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3
Q

Some plasma membrane receptors activate G-protein switch proteins that trigger a variety of 1. __________ or induce the generation of 2. ______________.

A
  1. Downstream pathways
  2. Intracellular second messagers
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4
Q

What do Tyrosine Kinases do?

A

Trigger signal transduction pathways involving sequential activation of downstream kinases.

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5
Q

Give three examples of hydrophobic signals in the cell.

A
  1. Steroids
  2. Retinoids
  3. Thyroxine
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6
Q

Give three examples of hydrophilic signals in the cell.

A
  1. Small molecules
  2. Peptides
  3. Proteins
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7
Q

Cells respond to environment signals such as?

A
  • Temperature
  • Light
  • Oxygen
  • Sounds
  • Odurs
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8
Q

Give examples of ways cells respond to signals from other cells.

A
  • Hormones
  • Growth factors
  • Neurotransmitters
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9
Q

What is signal transduction?

A

The process of sensing external stimuli and conveying the information to intracellular targets.

Extracellular signal –> Intracellular space

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10
Q

Describe the process of hydrophobic signalling molecules.

A
  1. Hydrophobic hormones diffuses through the cell membrane into the cytoplasm.
  2. In the cytoplasm, the hormone binds to a receptor/activator. Very often the receptor is a transcriptional activator residing in the nucleus
  3. The receptor-hormone complex is recognized by a transporter molecule that takes it to the nucleus.

Some receptors are in the nucleus and are activated by the hormone.

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11
Q

What is ‘Dex’? What does it activate?

A

Dexamethasone activates the Glucocorticoid receptor.

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12
Q

In the absence of ‘Dex’, where is the Glucocorticoid receptor.

A

In the cytoplasm

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13
Q

In the presence of ‘Dex’, where is the receptor-hormone complex moved to?

A

Moved to the nucleus when the hormone activates the receptor site.

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14
Q

The control b-galactosidase is _________ regardless of the presence of ‘Dex”.

A

Cytoplasmic

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15
Q

Hydrophilic signalling molecules work differently than hydrophobic signalling molecules. Describe the reaction that takes place to enter the cell and the nucleus.

A
  1. The binding of the signal molecule to a specific cell surface receptor changes he conformation (shape) of the receptor and its activation.
  2. The activated receptor initiates downstream signal transduction proteins and/or second messengers.
  3. Signal transduction leads to the activation of effector protein(s) causing:
  • Short term responses (Modification of cellular metabolism, function, movement)
  • Long term responses in the nucleus (Modification of gene expression, development)
  1. Termination (or down-regulation) from negative feedback or removal of the extracellular signal from the receptor.
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16
Q

Membrane receptors bind only a single type of _________ signalling molecules.

A

Hydrophilic

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17
Q

All hormone receptors are highly _______ for their ligands.

A

Specific

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18
Q

Each receptor binds only a ______ type of hormone.

A

Single

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19
Q

When a hormone binds to its specific receptor, the hormone changes the _________ of the receptor sending a signal to the cascade.

A

Conformation

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20
Q

Give examples of small molecules, peptides, and proteins that are used for hydrophilic signalling molecules.

A

Small molecules: Adrenaline, acetylcholine
Peptides: Glucagon
Proteins: Insulin, growth hormones

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21
Q

List the four types of extracellular signalling.

A
  1. Endocrine signalling
  2. Paracrine signalling
  3. Autocrine signalling
  4. Signalling by plasma-membrane attached proteins
22
Q

Describe endocrine signalling.

A

Affects target cells some distance from the site of synthesis.

  • Far proximity
  • Hormone gets secreted into the blood by the endocrine gland through the blood vessel and is secreted to the distant target cells
  • Uses the blood and blood stream
23
Q

Describe paracrine signalling.

A

Affects target cells in close proximity.

  • Uses secretory cells to secrete hormones to the adjacent target cell.
24
Q

Describe autocrine signalling.

A

Cells respond to the signals they produce. The target sites are ON the SAME cell.

  • Hormone produced by the SAME cell targets the receptor sites on that cell.
25
Q

Describe signalling by plasma-membrane-attached proteins.

A

The signalling cell it attached to the adjacent target cell and the hormones contact the specific receptor and they stay attached.

26
Q

Proteins can be modified by multiple protein ________ or ___________.

A

Kinases or phosphatases

27
Q

How can kinase/phosphatase activity be regulated?

A
  • Phosphorylation
  • Binding to other proteins
  • Binding of second messenger small molecules
28
Q

Phosphorylation can _______ or __________ protein function.

A

Activate or inhibit

29
Q

Specific protein phosphatases oppose the effects of kinase by _____________ .

A

Removing the phosphate .

30
Q

What are the two types of kinases in animal cells?

A

Tyrosine (Y) kinases and Serine (S)/Threonine (T) kinases

31
Q

Describe G proteins: GTPase switch proteins

A
  • Hydrophilic hormones bind to membrane receptors
  • The G-protien coupled receptors (GPCR) activate G-protiens (GTPase switch proteins)
  • G-protiens exchange GDP to GTP leading to a conformational change and activation
32
Q

An active G-protein sends a ___________.

A

Signal

33
Q

G-protein has intrinsic GTPase activity, which can be accelerated by _____________ (GAPs)

A

GTPase-accelerating proteins (GAPs)

34
Q

Once the initial signal is sent, the G-protein inactivates itself. How does it do this?

A

It inactivates itself y hydrolyzing GTP to GDP

35
Q

How is G-protein activity regulated?

A

It is regulated by the exchange of GDP to GTP.

36
Q

Does association with the GTP switches the protein on or off?

A

On.

37
Q

After sending the signal, GTP is ______ and the protein is switched “off”.

A

Hydrolysed.

38
Q

GTP fills the spot on the receptor active G protein, the signal is transduced, and an ________ dephsophorylates the GTP to produce GDP.

A

Inactivator protein

39
Q

Conformation of the G protein is altered by _______.

A

GTP/GDP binding.

40
Q

________ (GDP-bound) G protein is capable of interacting with upstream effector proteins.

A

Inactive

41
Q

______ (GTP-bound) G protein is capable of interacting with downstream effector proteins.

A

Active

42
Q

The downstream effector (often an enzyme) produces ______.

A

Secondary messager molecules.

43
Q

What is the role of secondary messengers?

A

Secondary messengers carry and amplify the signals from receptors (via G-protiens) to the effector molecules.

44
Q

Describe the characteristics of secondary messengers.

A
  • Short lived molecules
  • Diffuse rapidly
  • Allow enzymatic amplification
45
Q

Which of the following are water-soluble: Ca2+ ions, DAG, NO, cAMP, cGMP, IP3.

A

Ca2+ ions, cAMP, cGMP, IP3

46
Q

Which of the following are lipid-soluble: Ca2+ ions, DAG, NO, cAMP, cGMP, IP3.

A

DAG, NO

47
Q

What is the function of 3’,5’-Cyclic AMP (cAMP)

A

Activates protein kinase A (PKA).

48
Q

What is the function of 3’,5’-Cyclic GMP (cGMP)

A

Activates protein kinase G and opens cation channels in rod cells.

49
Q

What is the function of 1,2-Diacylglycerol (DAG)

A

Activates protein kinase C

50
Q

What is the role of Inositol 1,4,5-trisphosphate (IP3)

A

Opens the Ca2+ channels in the endoplasmic reticulum

51
Q

What happens when adenylyl class is activated by a stimulatory hormone and the G protein complex is activated by GDP?

A

cAMP is released.

52
Q

Describe the amplification of epinephrine down to the resulting product.

A

Epinephrine –> Adenylyl cyclase –> cAMP –> Protein kinase A –> Activated enzyme –> Product

MCB2050 Part 1 (13 decks)

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