Signal Transduction Flashcards
What is signal transduction?
relay of molecular or physical signals from a cell’s exterior to its interior leading to a cellular response.
Explain a Signal transduction..
- stimulus
- stimulated cell releases chemical messenger via transport protein
- chemical messenger binds to a receptor protein.
- Binding of messenger induces conformational change that elicits a response.
- Signal is terminated
Where do lipophilic/hydrophobic hormones bind?
Intracellular receptors.
Where do hydrophilic/lipophobic hormones bind?
Plasma membrane receptors.
Does a signal get stronger or weaker as it moves downstream?
Stronger/Amplified
What is micro-heterogeneity?
Means that a single ligand can elicit multiple, but coordinated, responses within a single cell.
How are signal transductions categorized?
By proximity to the target cell.
Explain endocrine signaling and list some examples.
Transport of molecules (hormones) through the bloodstream. –> travel long distances. Insulin, epinephrine, thyroxine, testosterone.
What are cytokines? Are they hormones?
Small signaling proteins secreted form non-glandular tissues and travel long distances. Not hormones but they travel the same way.
What is paracrine signaling?
Involves transport of signal molecules from secretory cells to its neighboring cells.
What is autocrine signaling?
The release of the signal from the send which contains its own target receptor.
Explain the release and binding of Acetylcholine.
- Action potential propagates through presynaptic neuron.
- Ca++ influx into presynapse
- ACh vesicles fuse with presynaptic membrane and release ACh into synaptic cleft.
- ACh binds to nicotinic receptors
- Na+ influx/ K+ outflux
- Postsynaptic action potential
- Nerve impulse/Muscle contraction
What kind of channel are nicotinic receptors on?
Ligand-gated
What does acetylcholinesterase do? What happens after this?
Breaks down ACh into choline and acetate. Choline is taken back into the presynaptic neuron to make more ACh.
What makes up ACh?
Choline and Acetyl CoA/Acetate.
What do acetylcholinesterase inhibitors do? What is an example?
Cause sustained skeletal muscle contraction. Neostigmine/organophosphorous
Myasthenia gravis is an autoimmune disease, usually caused by the production of antibodies to ACh receptors, resulting in inactivation of the receptors. A drug that may help to stabilize this condition would do which one of the following?
A. Stimulate the production of immune cells
B. Stimulate the production of epinephrine
C. Inhibit the production of acetylcholine
E. Inhibit monoamine oxidase
D. Inhibit acetylcholinesterase
What does an agonist do?
Binds to its receptor and elicits a specific response.
What does an antagonist do?
Binds to a receptor and prevents binding of agonists.
These channels often bind to neurotransmitters; the cellular response is to allow movement of ions across the cell membrane.
Ligand-gated Ion channels
When ligands bind, these receptors form dimers.
Enzyme-linked and Cytokine receptors
When ligand binds, these receptors activate and effector enzyme that cascades within the cell.
G-protein coupled receptors.
Can signaling molecules have different receptors on different tissues? If so, what’s an example?
Yes, ACh on nicotinic (skeletal muscle/ligand gated ion channel) and cardiac (muscarinic/GPCR).
Explain signal termination.
- inactivation of ligand-receptor complex
- loss of intermediates in the signaling pathway
- return of target proteins to their original state
