Cell Receptor & Signal Transduction Flashcards
What type of receptors are incorporated into the phospholipid cell membrane? They can be integrated with a number of intracellular proteins, enzymes, 2nd messengers and protein kinases
Membrane-bound receptors
Intracellular receptors are found in what 2 places?
Cytoplasm or nucleus
Signal transduction usually involves a _______ of events
A cascade of events
What is the fastest acting of all of the receptor mechanisms?
A membrane bound receptor that opens an ion channel
What is a drug that opens up Cl- channels?
Propofol
What type of receptor does propofol bind to?
GABA
A membrane bound receptor with signal transduction can be coupled with an enzyme and second messenger inside the cell to bring about a cell response.
These enzymes are what type of proteins?
Peripheral proteins
What is the first thing to happen after a ligand binds to a membrane bound receptor coupled with an enzyme and second messenger inside the cell? (What enzyme is activated)
Guanylate cyclase is activated
What does the activated enzyme guanylate cyclase do to GTP?
Converts GTP to cyclic GMP (cGMP)
What does cGMP activate that brings about the cellular response?
Protein kinase G
What type of enzyme can inactivate second messengers, such as cGMP, causing cGMP to break down to GMP and cease of cell response?
Phosphodiasterases
Guanylate cyclase is no longer activated when?
When the ligand is removed from the receptor site
A G-protein is coupled with a membrane bound receptor and is composed of what 3 subunits?
Alpha, beta, and gamma subunit
Which subunit is attached to GDP?
Alpha subunit
What happens to the G protein/alpha subunit when a chemical signal binds to the receptor
It separates from the receptor, GTP replaces GDP on the alpha subunit and it separates from the other subunits
What brings about the physiologic response with G protein coupled receptors?
The alpha-GTP complex
Other than separation of the chemical signal from the receptor site, what ceases physiologic response in G protein coupled signal transduction?
A dephosphorilating enzyme in the alpha subunit breaks down GTP to GDP. The alpha/GDP complex reconnects with the G protein which reconnects to the receptor and becomes inactive.
What type of receptors use G protein coupled receptors
Alpha 1
Beta 1
Beta 2
Activated Alpha 1 receptor alpha/GTP complex activates what enzyme?
Phospholipase C
Activated Phospholipase C converts PIP2 into what two substances?
Diacylglycerol
IP3
IP3 causes increased release of _______ form sarcoplasmic/endoplasmic reticulum
Calcium
Diacylglycerol and the Calcium released from IP3 stimulation activate ___________ to get target cell response.
Protein kinase C
Alpha 1 receptors are found predominantly where?
Vascular smooth muscle
Pure A1 agonist drug
Neosynephrine
Activated A1 response brings about what physiologic actions
Vascular smooth muscle contraction -
Vascular constriction -
Increase BP
B1 receptors are found where in the heart?
SA node
AV node
Ventricular contractile fibers
Activated B1 in the SA node causes:
Increased HR
Activated B1 in the AV node causes:
Increased speed of conduction
Activated B1 in ventricular contractile fibers causes:
Increased contractility
B2 receptors are found where?
Bronchiolar smooth muscle
Activated B2 in bronchial smooth muscle causes:
Bronchiolar dilation and increased airflow
What is a common B2 agonist we use for bronchiolar dilation?
Albuterol
The alpha/GTP subunit activates what enzyme in B receptors
Adenylyl cyclase
Adenylyl cyclase converts ATP to cAMP in order to activate what enzyme to bring about physiologic response to activated B receptor
Protein kinase A
If a receptor is phosphorilated to activate intracellular proteins, that means that _______ is added to bring about target cell response.
Energy is added to bring about target cell response
What steroid-based hormones use intracellular receptor mechanisms
Testosterone Aldosterone Progesterone Estrogen Cortisol
What hormones also use intracellular receptor mechanism, but is not steroid based?
Thyroid hormones
A steroid based hormone crosses the cell membrane to bind with intracellular receptor, what does the hormone/receptor complex do next?
Moves through nuclear pores into the nucleus
Once in the nucleus, the aldosterone/receptor complex attaches to DNA and activates ____________.
Transcriptases
Transcriptases are enzymes that do what?
Increase the rate of transcription of DNA to mRNA
What does mRNA have to do in order to synthesize proteins?
Leave the nucleus and carry the code to synthesize proteins
What brings about the target cell response in intracellular receptor mechanisms?
The proteins synthesized/produced.
Intracellular receptor mechanisms take seconds to minutes to work. TRUE/FALSE?
FALSE
Take hours to days to work, but last longer than other mechanisms
What vasodilating substances use membrane bound receptor and intracellular receptor signal transduction mechanism?
Histamine
Bradykinin
Prostaglandins
Adenosine
Signal transduction via opening of cell membrane ion channels is the fastest signal transduction mechanism by far, this occurs in ___________
Milliseconds
Signal transduction mechanisms coupled with second messengers, G-proteins, and phosphorylation of intracellular proteins/enzymes all occur take how long to get target cell response?
Seconds to minutes
Intracellular receptors take how long to get target cell effect?
Minutes, hours or days, but long-lasting effects.
