Pharmacology Flashcards
(57 cards)
What is signal transduction?
When a chemical messenger is released from one cell and binds to a receptor on another cell to initiate a response within it
What does signal transduction allow?
Coordination
Integration
How do chemical messengers target specific cells and only produce a response within these cells? What does this allow?
They receptors on these specific cells will have a complementary shape with the chemical messenger
Specificity, which means that all cells won’t carry out the same function but rather specialised functions
Can two cells with the same receptor carry out different responses when the chemical messenger binds to them?
Yes
Can cells have several different receptors for the same chemical messenger? Why?
Yes, this means they can trigger several different responses within the same cell
What classification of chemical messengers are able to pass through the phospholipid bilayer?
Hydrophobic/Lipophillic
Where are the receptors for hydrophobic messenger founds?
Within the cell
How are hydrophobic messengers transported through the blood?
Bound to a protein in the plasma. When the messenger passes a cell with the appropriate intracellular receptor, their affinity for this binding protein will decrease, causing them to unbind and move through the phospholipid bilayer to bind to it
Name two hydrophobic messengers
Steroid hormones
Nitric oxide
What are steroid hormones?
Hydrophobic messenger
Bind to intracellular receptors found on DNA. When they bind to the DNA they can alter the rate of gene transcription
What is nitric oxide?
Hydrophobic messenger
Binds to soluble guanlyl cyclase, which is a type of intracellular receptor. When it binds to this receptor it will generate cGMP, which is a phosphate that acts as a second messenger and regulates cell activity
What are second messengers?
Chemical messengers that are created after the extracellular chemical messenger binds to its receptor. These messengers are involved in initiating a response within the cell. They apply to both extracellular and intracellular responses.
What chemical messengers are unable to pass through the phospholipid bilayer?
Hydrophilic/Lipohobic
Where are the receptors of hydrophilic chemical messengers found?
Surface receptors in the plasma membrane of the cell
What are the four types of surface receptors?
Ionotropic receptor
Receptor kinases
Non-receptor tyrosine kinases
G-protein coupled receptor
What are ionotropic surface receptors? How do they work?
Recptors which are part of an ion channel
When their chemical messenger binds, it will result in the ion channel opening or closing, which will affect the ion concentration inside and outside the cell (membrane potential). This will result in a cellular response, which is normally to stimulate fast IPSP and EPSP
What are receptor kinases? How do they work?
Receptors which have an enzyme (tyrosine kinase ) physically built into their structure.
When their chemical messenger binds, the tyrosine kinase is either activated or inactivated, which either stimulates or inhibits tyrosine kinase from phosphorylating its substrate . This results in a cellular response, which is usually to stimulate proliferation or differentiation
What are non-receptor tyrosine kinase receptors? What type of enzyme is involved? How do they work?
Receptors don’t have the kinase enzyme physically built into its structure but instead the enzyme is bound onto it.
JAK kinase
When their chemical messenger binds, the JAK kinase is either activated or inactivated, which either stimulates or inhibits tyrosine kinase from phosphorylating its substrate . This results in a cellular response, which usually affects protein synthesis
What are G-protein coupled receptors? How do they work?
Receptor that have a G-protein attached to them.
When their chemical messenger binds, a subunit of the G-protein is displaced across the membrane and will bind to another protein. This stimulates a cellular response
Describe the structure of G-proteins
Made up of seven transmembrane spanning segments. Sometimes segments are seen in the plasma membrane
Explains why G-proteins are referred to as 7TM
Describe the mechanism of G-protein coupled receptor which is coupled to adenylyl cyclase
When the chemical messenger binds, activates G-protein.
Results in the alpha-subunit of the G-protein displacing itself across the membrane so that it can bind to the enzyme, adenylyl cyclase.
When the alpha-subunit is bound to adenyl cyclase, produces a second messenger, cAMP
cAMP regulates the activity go another enzyme, PKA.
cAMP will activate PKA, which causes it to phosphorylate a protein as it is a kinase enzyme
The phosphorylated protein can cause a cellular response, which can vary
Describe the mechanism of G-protein coupled receptor which is coupled to phospholipase C
When the chemical messenger binds, activates G-protein.
Results in the alpha-subunit of the G-protein displacing itself across the membrane so that it can bind to the enzyme, phospholipase C
When the alpha-subunit is bound to adenyl cyclase, produces two second messenger, IP3 and DAG
IP3 and DAG both activate PKC, but IP3 does it out indirectly and DAG carries it out directly
IP3 has to release Ca2+ ions from the endoplasmic reticulum in order to activate PKC
PKC will phosphorylate a protein, as it is a kinase
The phosphorylated protein can cause a cellular response, which can vary
Why does double activation of PKC occur?
Two secondary messengers activate it
What secondary messengers are associated with phospholipase C?
IP3 and DAG
