Medicine Sem 2 > Molecular biochemistry W12 > Flashcards

Molecular biochemistry W12 Flashcards

(42 cards)

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1
Q

Name the 5 different mechanism of intracellular communication

A
  • Contact-dependent (Juxtacrine) signaling
    -Paracrine signaling
    -Synaptic signaling
    -Endocrine signaling
    -Autocrine signaling
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2
Q

Name 2 key components required for signaling

A

-Ligand
-Receptor

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3
Q

What is a ligand

A

A molecule that binds to a receptor

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4
Q

What is a receptor

A

A protein thar=t binds to a ligand to trigger a cellular response

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5
Q

What does contact -dependent(Juxtacrine) signaling require

A
  • Direct cell to cell membrane contact
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6
Q

What does paracrine signaling involve

A
  • Local mediators acting on nearby cells
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7
Q

Explain what happens in Synaptic signaling

A

-neurons transmit electrical signals and reease neurotransmitters at distant synapses

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8
Q

In endocrine signaling what does encorine cells release, to where and why

A

Endocrine cells release hormones into the bloodtsream to reach distant targets

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9
Q

Name 2 types of receptors

A
  • Cell surface receptos
    -Intracellular receptors
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10
Q

What are cells surface receptors for

A
  • For large or hydrophilic molecules that cant pass through the membrane
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11
Q

What are intracellular receptors for

A

For small, hydrophobic molecules that can cross the membrane

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12
Q

Explain the steps in signal processing , starting from a Ligand

A
  • Ligand binds to a receptor on the target cell
    -Once ligand binds, the receptor chsnges chape or structureo this is cslled activation
    -The activated receptor triggers intracellular signaling pathways
    -Then at the end of the signaling pathways, effector proteins are activated , which change the cell behaviour
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13
Q

Give examples of effector proteins

A

-Transcription regulators
-Ion channels
-Metabolic enzymes
-Cytockeleton proteins

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14
Q

Explain specificity and response in signal processing

A

-Each cell has specific receptors for particular ligands

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15
Q

Name a type of intracellular receptor

A

Cytosolic receptors

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16
Q

In cytosolic receptor signaling what are ligands

A

They are lipophilic molecules

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17
Q

Explain the process that takes place in cytosolic receptor signaling startign from a ligand

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A
  • A ligans diffused through the cell membrane and binds to receptors in cytosol
    -This forms the hormone-receptor complex
    -The hormone -receptor comples then:
    The hormone–receptor complex:

Enters the nucleus.

Dimerizes (forms a pair).

Binds to Hormone Response Elements (HREs) on DNA

Acts as a transcription factor, starting gene transcription.

Leads to mRNA synthesis, then protein production in the cytosol.

18
Q

What are steroid hormones derivied from and are they hydrophobic or hydrophilic

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A
  • Derived from cholesterol
    -They are hydrophobic
19
Q

Name the 3 types of membrane rececptors used by hydrophillic ligands

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A
  • Ion-channel-coupled receptors
    -G- Protein-coupled receptoes (GPCRs)
    -Enzyme-coupled receptors
20
Q

When does ion-channel-coupled receptors open

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A

-They open when a ligand binds, allowing ions to pass through

21
Q

What is G-protein-couple receptors linked to + explain what happens once a ligand binds

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A
  • Linked to a G protein which binds to GDP/GTP
    -Ligand binind activates the G protein, triggering signaling cascades
22
Q

Explain the characteristics of enzyme couple receptors + what ligand binding activates

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A
  • Either have enzymatic activity themselves or are associated with enzymes
    -Ligand bindign activates enzyme function and starts signaling
23
Q

Name the 3 stages of signaling with second messengers

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A
  • Reception
    -Transduction
    -Response
24
Q

Explain what happens in the Recepetion stage of signaling with second messengers starting with a ligand

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A

-The ligand binds to a specific membrane receptor
-This activates the receptor and starts the signaling process

25
Explain what happens in the transduction stage of signaling with the second messenger
-The activated receptor triggers a signaling cascade inside the cell -Second messengers are produced , this causes a signal amplification
26
What happens in the Response stage of signaling with second messengers
- The cascade leads to activation of target proteins -This causes a change in cell behavior
27
Explain what happens in signal transduction via cascades staring with a ligand
Signal Transduction via Cascades: The ligand (1st messenger) binds to a membrane receptor. Receptor activates enzyme 1, which produces a 2nd messenger. 2nd messenger activates enzyme 2, which synthesizes the final product. Each level amplifies the signal further.
28
What are second messengers+ function
Intracellular molecules that respond to extracellular signals - They amplify the signal inside the cell
29
What is the function of kinases
Add phosphate to proteins
30
What is the function of phosphatses
- Remove phopshates
31
G-proteins are activate when bound to what? They are inactive when bound to what?
- Active when bound to GTP -Inactive when bound to GDP
32
Name the types of cellular responses
- Slow response - Fast response -Very fast response
33
What does slow cellular reponses involve + how long does it take
- Involve gene expression and new protein synthesis -Takes an hour or more
34
What does fast cellular response : -Not involved in -How long does it take -What does it involve -What is it often triggered by
- Do not involve gene transcription. Happen in seconds to minutes. Involve things like cell movement, secretion, metabolism. Often triggered by rapid phosphorylation of cytoplasmic proteins.
35
How long does it take for very fast cellular resposes to occur and via what changes
- Occurs in milliseconds via changes in membrane potential
36
Name the 2 different types of hormones + charcateristics
- Hydrophobic hormone- lipophilic -Hydrophilic hormone - water soluble
37
What does hydrophobic hormones: -bind to -what level do they work at -What type of affects do they cause
-Bind to intracellular receptors -Work at the DNA lebel -Cause long term, delyaed effects
38
Where is Hydrophobic hormones inactivated and excreted
Inactivated in live Excreted in bile
39
What does hydrophillic hormones : -Bind to -How do they act -Where are the stored + when are they released
- Bind to cell surface receptors -Act quickly -Sored in secretory granules and released when needed
40
Give an example of hydrophilic hormones
- Catecholamines
41
What is the purpose of adaption/desensitization of a signal
-It orevents overstimulation by the same signal
42
Name the 5 processes that adaptaion and desensitization can happen through
- Receptor inactivation -Receptor down -regulation -Surface receptor inactivation -Changes in intracellular signaling proteins -Inhibitor protein production
Medicine Sem 2
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