Term
What is signal transduction? |
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Definition
Communication between cells; language cells use to organize themselves
-Influences cell behavior
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Term
signal transduction in multicellular organisms |
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Definition
-Co-ordinates function within an organ, between organs, and during development
-Errors in signaling are responsible for many diseases; diabetes
and cancer
-Uses proteins closely related to those used in unicellular organisms, but much more complex
-Mainly via extracellular signaling molecules (exceptions)
Note exception: displayed on external surface of cell
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Term
Signal Transduction: General Principles Summary |
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Definition
•Mainly accomplished via extracellular signal molecules
•Most cells both emit and receive signals
•Reception of the signal depends on a receptor
•The receptor activates one or more intracellular signaling proteins to relay the signal
•Different types of cells can respond differently to the same extracellular signaling molecule
•Each cell is programmed to respond to specific combinations of extracellular signal molecules
•Cells can adjust their sensitivity to chemical signals
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Term
Receptors can be intracellular |
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Definition
1. Intracellular receptors
A. signal is hydrophobic
Example: Steroid hormones such as androgen
-intracellular receptors are ligand-activated transcription factors (androgen receptor)
B. Signal is a gas
Example: nitric oxide
-Intracellular receptor;
guanylyl cyclase
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Term
Receptors can be on the cell surface |
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Definition
2. Cell Surface Receptors
-Bind to hydrophillic signaling molecules
-The three largest groups
1. Ion-channel linked receptors
-rapid synaptic signaling
-mediated by neurotransmitters
2. G-protein-coupled receptors
-indirectly regulate the activity of
membrane-bound target proteins
3. Enzyme-coupled receptors
-enzymes or are linked with enzymes
-heterogeneous class
-most are protein kinases
(or associated with protein kinases)
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Term
Why does the specific way a cell reacts to its environment vary?
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Definition
-Types of receptors
-Intracellular machinery (proteins that integrate and interpret the signals).
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Term
Animal cells are exposed to and depend on many extracellular signals |
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Definition
Typical mammalian cell is exposed
to hundreds of different signals
-signal molecules work in combination
1. Multiple signals required for survival
2. Additional signals required for proliferation
or differentiation.
3. Deprivation of survival signals leads to
cell death.
-respond selectively
1. Each cell has a set of receptors
2. Receptors allow cell to respond to a
set of signal molecules
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Term
Six required steps for communication between cells |
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Definition
1. Synthesis of a signaling molecule by a signaling cell
2. Release of the signal molecule
3. Transport the signal to the target cell
4. Detection of the signal by the target cell
5. Transmit the signal within the cell (2nd messengers/Po4 events)
-read and understand the signal
-alter behavior to fit signal
6. Remove signal (usually terminates the cellular response)
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Term
generalized intracellular signaling pathway activated
by an extracellular signal |
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Definition
1. Receptor; signal transducer
-binds ligand
-converts into one or more
intracellular signals that alters behavior
2. Transmission of the signal relies on
intracellular signaling proteins and small
intracellular signaling molecules (2nd messengers)
-intracellular signaling molecules
mostly are of one or two kinds:
A. proteins that become
phosphorylated by protein kinases
B. proteins that are induced to
bind GTP when the signal arrives
-second messengers; cAMP, Calcium etc..
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Term
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Definition
signaling molecules (or their modifications) have a rapid turnover in the cell
1.Lifetime of a signaling molecule or a modification is short
- rapid changes in cellular concentration of the signaling molecule
-rapid response to the signal and a rapid termination of the signal
2. Accomplished by
-enzymes that remove the modification (phosphatases),
-enzymes which degrade the intracellular signaling molecule or
-enforced confirmation changes in the intracellular signaling molecule
which inactivate it.
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Term
Cells can adjust their sensitivity to a signal; desensitization |
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Definition
1) Receptor Sequestration
2) Receptor Down- Regulation
3) Receptor Inactivation
4) Inactivation of Signaling Molecule
5) Production of Inhibitory Protein |
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