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MED 103- BIOLOGY I > 30. TRANSDUCTION > Flashcards

30. TRANSDUCTION Flashcards

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1
Q
  1. What is Transduction?
A
  • the signal from the receptor is converted to a different
    form
  • this form can cause a specific cellular response
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2
Q
  1. What does Transduction require?
A
  • it usually requires a series of changes
  • these happen in a series of different target molecules
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3
Q
  1. What are Signal Transduction Pathways?
A
  • they are cascades of molecular interactions
  • they relay signals from receptors to target molecules in
    the cell

CASCADES: a series of enzymic reactions
: at each step, they convert an inactive
enzymes into an active enzyme

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4
Q
  1. Within a Signal Transduction Pathway, what happens at each step of the pathway?
A
  • the signal is transduced into a different from
  • this is usually a conformational change in the protein

CONFORMATIONAL= change in shape

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5
Q
  1. What do many signal pathways include?
A
  • Phosphorylation Cascades

Eg: MAPK Signalling Pathway
: this is activated by a growth factor receptor

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6
Q
  1. Which enzymes are present during the Process of Phosphorylation?
A

PROTEIN KINASES:
- these are the enzymes that add a phosphate to the
next protein kinase in line
- they activate protein kinases

PHOSPHATASES:
- these are the enzymes that remove the phosphates
- they deactivate the protein kinases

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7
Q
  1. Provide a description for Label 1.
A
  • a relay molecule activates Protein Kinase 1
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8
Q
  1. Provide a description for Label 2.
A
  • the active Protein Kinase 1 transfers a phosphate
  • it transfers it from ATP to an inactive molecule of
    Protein Kinase 2
  • this activates the Second Kinase
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9
Q
  1. Provide a description for Label 3?
A
  • the Active Protein Kinase 2 catalyses the
    phosphorylation
  • this speeds up the process
  • it also catalyses the activation of Protein Kinase 3
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10
Q
  1. Provide a description for Label 4?
A
  • the Active Protein Kinase 3 phosphorylates a protein
    (the pink one in this case)
    ⁺
  • this brings about the cell’s response to the signal
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11
Q
  1. What are the Second Messengers?
A
  • they are small molecules and ions
  • they are non-proteins
  • they are water-soluble
  • they act in the signal transduction pathways
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12
Q
  1. What are two examples of Second Messengers?
A
  1. cAMP
  2. Ca²⁺
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13
Q
  1. What is Cyclic AMP (cAMP)?
A
  • it is a Second Messenger
  • it is produced from ATP through the enzyme Adenylyl Cyclase
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14
Q
  1. What do many G-Proteins Trigger?
A
  • they trigger the formation of cAMP
  • cAMP acts as a Second Messenger in the Signal
    Transduction Pathways
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15
Q
  1. When do Calcium Ions (Ca²⁺) act as Second Messengers?
A
  • when they are released into the Cytosol of a cell
  • they act in many different pathways
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16
Q
  1. Why are Calcium Ions important Second Messengers?
A
  • they are cells that are able to regulate their concentration in the Cytosol
17
Q
  1. What are some other examples of Second Messengers?
A
  1. Diacylglycerol (DAG)
  2. Inositol Triphosphate (IP₃)
18
Q
  1. What does IP₃ trigger (Inositol Triphosphate)?
A
  • it triggers an increase in Calcium Concentration in the cytosol
  • when this occurs in the Smooth ER
  • it can prevent cancer or try to stop it
19
Q
  1. Provide a description for Label 1.
A
  • a signal molecule binds to a receptor
  • this leads to the activation of Phospholipase C
20
Q
  1. Provide a description for Label 2.
A
  • Phospholipase C cleaves a plasma membrane phospholipid
  • this phospholipid is called PIP₂
  • it is cleaved into DAG and IP₃
21
Q
  1. Provide a description for Label 3.
A
  • DAG functions as a Second Messenger
  • it does this in other pathways
  • DAG activates PKC
  • PKC goes on to Phosphorilate many targets
22
Q
  1. Provide a description for Label 4.
A
  • IP₃ quickly diffuses through the cytosol
  • it binds to an IP₃ Gated Calcium Channel
  • this happens in the ER membrane
  • this causes the channel to open
23
Q
  1. Provide a description for Label 5.
A
  • the Calcium ions flow out of the ER
  • they flow down their concentration gradients
  • this raises the Ca²⁺ level in the Cytosol
24
Q
  1. Provide a description for Label 6.
A
  • the calcium ions activate the next protein
  • they do this in one or more signalling pathways
25
Q
  1. What is the Response?
A
  • the transduced signal triggers a specific cellular response
26
Q
  1. What does Cell Signalling lead to?
A
  • it leads to the regulation of cytoplasmic activities
  • this is known as a Cytoplasmic Response
  • it can also lead to Transcription
  • this is known as a Nuclear Response
27
Q
  1. In the cytoplasm, what are cell signalling pathways responsible for regulating?
A
  • a variety of cellular activities
28
Q
  1. What is the Nuclear Response to a signal?
A
  • this is when other pathways regulate genes
  • they do this by activating transcription factors
  • these turn gene expressions on and off

EG: steroid hormone signalling pathways
: MAPK signalling cascades

29
Q
  1. What are the two important benefits of Multistep Signalling Pathways?
A
  1. Amplification of the Signal
    - this is the amplification of the response
    - this contributes to the specificity of the response
  2. Provides more opportunities for:
    • co-ordination
    • regulation
30
Q
  1. What is Signal Amplification?
A
  • each protein in a signalling pathway amplifies the signal
  • it does this by activating multiple copies of the next component in the pathway

AT EACH STEP:
- the number of activated products is much greater in the preceding step

31
Q
  1. What is meant by the Specificity of Cell Signalling?
A

DIFFERENT KINDS OF CELLS:
- have different types of Proteins

DIFFERENT PROTEINS:
- allow for cells to detect and respond to different
signals

EVEN THE SAME SIGNAL:
- can have different effects in cells with different
proteins and pathways

32
Q
  1. What gives the cell great specificity?
    What is this specificity found in?
A
  • the different combinations of proteins in a cell
  • the specificity is found in:
    • the signals the cell detects
    • the responses it carries out
33
Q
  1. What is Pathway Branching and Cross Talk?
A
  • this helps the cell to further co-ordinate incoming signals
34
Q
  1. What are Scaffolding Proteins?
A
  • they are large relay proteins
  • they are attached to other relay proteins
35
Q
  1. What is the function of Scaffolding Proteins?
A
  • they increase the signal transduction efficiency
  • they do this by grouping together different proteins
  • these proteins are all involved in the same pathway
  • they also help to make a more efficient activation of signalling pathways
36
Q
  1. What terminates the signal response quickly?
A
  • the reversal of the ligand binding
  • the ligand is releases from the receptor
37
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes

MED 103- BIOLOGY I (53 decks)

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