Cell signaling: Receptors and messengers Flashcards
(22 cards)
Specificity
Membrane receptor binds only one type of chemical messenger
Affinity
The strength with which a chemical messenger binds
Saturation
The degree to which receptors are occupied by a messenger. If all occupied, saturated.
Function of the EC receptors
- Bind chemical messengers from outside environment
What are chemical messengers called
ligands
What does binding of a ligand cause
An intracellular response
What is an intracellular receptor
A receptor located in the cytoplasm of the cell. Binds ligands within the cell and then takes the receptor to the nucleus to initiate transcription
What types of molecules bind easily with IC receptors
Lipid soluble (fats) and nonpolar - cross membrane easily
What types of molecules need to be brought into the cell
Water soluble molecules
Lipid-soluble first messenger
Able to cross membrane. Bind to receptors inside the cell
Water-soluble first messenger
Not able to cross the membrane, must first bind to the plasma membrane. Involves secondary messengers (i.e. kinases)
Water-soluble second messenger
Released in response to exposure of the first messenger, occurs inside the cell. Induces signal transduction cascade, i.e. - cAMP
What function do Ca+ and cAMP serve
The act as second messengers and mediate downstream cell effects. cAMP binds to cAMP dependent protein kinases.
Where is Ca2+ usually found
In the cytosol, in very low levels
Where does Ca2+ usually diffuse from
from the membrane and ER, usually via calcium channels
What is the role of Ca2+
2nd messenger and acts as an electrical stimuli.
What is different about Ca as a second messenger
Binds to calmodulin and combines with and alters response proteins directly
What are eicosanoids
Family of molecules that are used in inflammatory process. Derived from arachidonic acid metabolites (2 enzymes)
How are arachidonic metabolites made?
Acid is cleaved from the phospholipid membrane by phospholipase, then are processed into cyclooxygenases and lipoxygenases
How is the eicosanoid pathway interrupted
It can be manipulated by aspirin and other NSAIDs by inhibiting the enzymes cyclooxyrgenase and lipooxygenase
Allosteric activator (modulation)
A molecule that binds to an enzyme and changes the active site to bind an appropriate substrate. Can be an activator or deactivator. controls cell function
Covalent modulation
The addition and/or elimination of molecules that attach to the enzyme (protein). Best example of these types of molecules is phosphorylation
