Chap 5(Signal Transduction Mechanisms) Flashcards
What is signal transduction mechanism?
Process by which messenger binding to receptor produces response in target cell
Signal transduction mechanism differs based on what ?
whether messenger is lipophilic or lipophobic
Lipophillic Messenger located where?
Receptor inside cell
Lipophobic messenger located where?
Receptor on plasma membrane
Lipophillic messengers bind to receptor where? What occurs if it is in cytoplasm?
In cytoplasm or nucleus.
Receptor :messenger complex enters nuclues
Lipophobic messengers bind to what?
Membrane-bound receptors
Define signal transduction.
the transmission of molecular signals from a cell’s exterior to its interior
Lipophobic messengers , receptors fall into three categories, name them.
Channel linked receptors
Enzyme linked receptors
G protein linked receptors
What is a channel linked receptor
Receptor that opens/closes ion channels in response to messenger binding
Can gated ion channels open and close?
Yes.
Ligand- gated channels open or close in response to what?
Binding of ligand to receptor
What is a ligand?
Messenger that bind to recepto/channel
Channel-linked receptor is what ?
Type of ligand- gated channel
Open channel means what ?
Increased permeability
Fast channels mean what
Receptor and channel are the same protein
Slow channels mean what?
Receptor coupled to channel by G protein
What is the role of calcium in signal transduction (4)
Changes electrical properties of cell
Induces muscle contraction
induces secretion by exocytosis
binds to calmodulin
Ca-Calmodulin complex activates what ?
Protein Kinase
Calcium levels cytosol and extracellular fluid
Lower in cytosol
Calcium level is maintained at low level because of:
- active transport of calcium across membrane.
- Sequestration of calcium by binding with proteins in cytosol.
- active transport of calcium into certain organelles( Smooth endoplasmic reticulum and mitochondria)
How are calcium levels in cytosol increased?
by opening ion channels or releasing intracellular stores
Enzyme linked receptors special how?
Function as enzyme and receptor
Most enzyme linked receptors are
tyrosine kinase
Purpose of G protein
function as links between G-protein-linked receptors and other proteins in plasma membrane called effectors.
What is a second messenger?
An intracellular messenger produced by binding of an extracellular messenger to a receptor
How is second messnger produced? Involves what?Purpose?
Binding of first messenger to receptor leads to production of second messenger in the cytosol. G-proteins. Amplification.
What is phosphodiesterase?
Enzyme that degrades c-AMP
What is the amplifier enzyme?
Guanylate Cyclase
What is Phosphatidylinositol biphosphate (PIP2)
Membrane phospholipid
What is phospholipase C? Activated by what?
Amplifier enzyme. G protein.
How does termination of message occur?
Enzymatic degradation of messenger
Diffusion of messenger away from receptor
Internalization of messenger-receptor complex
Removal of calcium from cytosol
How does signal transmission occur in endocrine system?
Endocrine gland releases hormone into blood
Travels to distant target cells
