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MCPHS MEDCHEM 1 E2

MCPHS - MedChem I Exam 2 (b)

QuestionAnswer
What is the sequence off events that occur with mechanisms of action of drugs? Endogenous ligand or Drug, Molecular = target, Cellular = Signal Transduction, Tissue = alt. Function, System = alt. Parameter
Example of NO (Nitric Oxide) mech. of action? NO, Stim: Guanylate Cyclase, Increases Cyclic GMP, Smooth Muscles Relax, Decreases BP
What kind of targets are there? Specific (Quinine elim Plasmodium) reduced Fever, Non-Specific (Tylenol Re-Set Temp Reg Center, but no cure) lowers Fever only, Both = Tx's Sx & Cures Disease (Quinine also resets Temp Reg Center, so it does both)
How many diseases actually cured? 26, so Tx'ing Sx's most of the time
Where are targets located? Extracellular, Cellular, Intracellular
example: Extracellular? Heparin & coagulation proteins, Ca/Mg Caronate & HCl (effect: decrease clotting or stomach acidity) *(Mech. of Action: Neutralization of co-agulation protiens or neutralization of Hydroprotic Acids)
What are Targets? Enzymes, Carrier Molecules, Ion Channels, Receptors (The Nature of all these targets is that they are all proteins)
example: Enzymes? Nitric Oxide on guanylate cyclase, or captopril on Angiotensin Converting Enzymes (ACE)
example: Carrier Mol? Reserpine on Catecholamine trans, Omeprazole on Proton Pump (Inhibits Na/H pump)
example: Ion Chan? Nifedipine on Ca chan.'s, General Anesthetics on K chan.'s
example of Cellular Targets? Ach on Ach Rcptr (effect: Contraction of muscle) Curar on ACh Rcptr (effect: Prevents Muscle Contraction)
example of Intracellular Targets? Sulfa Drugs (effect: Inhibit bac growth), AntiCancer Drugs (effect: Inhibition of cell replication)
example of Receptors? ACh on Nicotanic & Muscarinic Rceptrs, or N.E. on alfa & beta Rcptrs
Who introduced the concept of "Receptive Substance"? John Langley (1878)
Who coined the term "Receptor"? Paul Ehrlich (1909) Drug = 1st Messenger & Stimulated Effects inside a cell are caused by 2nd Messenger
Definition of Receptor? Macromolecular component of a cell that interacts w/ a drug and initiates the chain of events leading to the drug's observed effect.
Where may Receptors be present? Cell Membranes (Dopamine, ACh Rcptrs), Cytoplasm (Glucocorticoid), Nucleus (Steroid Hormone Rcptrs)
What do Drug-Receptor Interactions do? Signal transduction (Simulates or blocks endogenous signaling)
What does Imantinib do? It is a cancer drug that Inhibits Phos.- Kinase by binding with AA residues with many weak vander wall and H-bonds Similar to the way enzyme-substrates interact
Drug-Receptor interactions resemble? Enzyme-Substrate Interactions
Intial therory of Drug-Receptor Interactions ? Lock & Key Static Fit Model
New Dynamic D-R Interaction Therory? Induced Fit Model (Dynamic Interactions = both able to conform a little to accomodate the other)
What is the name of receptor changes in shape? Induced optimal binding by ligand
Four Types of Receptors? Ligand-Gated (Chollnergic Nicotinic Rcptrs), G Protein-Coupled Rcptr (alpha & beta Adreno-Rcptrs), Enzyme-Linked Rcptrs (Insulin Rcptrs), Intracellular Rcptrs (Steroid Rcptrs)
What are Ligand-Gated Ion Chan Rcptrs Also Called? Channel Linked Receptors
What do Chan. Linked (Ligand-Gated Ion Chan.) Receptors do? Cause changed in Ionic Membrane Potential
What are G-Protein Coupled Rcptrs also Called? G-Protein cpld rcptrs AKA "Metabotropic Receptors"
What do G-Proteins Coupled Receptors do? G-Pro Cpl'd Rcptrs Phosphorylate Proteins
What do Enzyme-Linked Rcptrs do? Protein & Receptor Phosphorylation
What do Intracellular Rcptrs do? Protein Phosphorylation & alt. Gene Expression
How many times does G-Pro-Cpl'd Rcptrs Span the Membrane? 7x's
how many time does Enzyme Linked Rcptrs Span the Membrane? 1x
What kind of Responce does Ligand-Gated Ion Chan. (Chan. Linked) Rcptrs have? Ligand-Gated respond RAPID/FAST (milliseconds)
What are some examples of Ligand-Gated Ion Chan.? nACh, GABAa, NMDA, Glycine rcptrs
What is the structure of Ligand-Gated Ion Chan? "Oligomeric" 5 subunits (2 alpha, 2 beta, 1 gama) can be in any order
What are some functions of Ligand-Gated Ion Chan? Neurotransmission, Cardiac Conduction, Skeletal Muscle Contraction
What do alpha subunits tell you about the number of binding sites? alpha subunits = # of binding sites on Ligand-Gated Ion Chan.
How many Trans-Membrane (TM) domains can a subunit be made out of? 4 TM domains per subunit, where TM2 compose the inside gates of the ion channel
When ligand binds to ion chan rcptr what does it do? Causes "Conformational" change in gate/pore by rotating the subunits
Where are Nicotinic ACh (nACh) Rcptrs found? nACh rcptrs found on NeuroMuscular (NM), Autonomic Ganglia (AG), & CNS
How many ACh's does it take to open ion gate of nACh gate? 2, the first one promotes binding of another mol. to 2nd. Known as "Receptor Cooperativity"
What is ACh on nACh gate? ACh is a skeletal muscle stimulator
Why is ACh a stimulator on ion gate? opens gate causing Na+ to move in depolarizing neuron
Where are GABAa receptors found? GABAa rcptrs are found in CNS (Spinal Cord, hypothalamus, hippocampus, substantia nigra, cerbral & cerebellar cortex)
What Ion moves down gradient thru GABAa channels? Cl- moves thru GABAa chan. to Hyperpolarize inside of nueron (inhibiting AP's)
How do GABA a receptors interact with Benzodiazepines & Barbiturates? Benzodiazepines & Barbiturates = Allosteric Modulation w/ GABAa
What is the effect of Cl- moving in to CNS via GABAa? Decreased Anxiety/Convulsions
What is the structural shape of GABAa? Pentameric
Where are agonist sites located on GABAa? Between alfa & beta subunits
where are benzodiazepine binding sites on GABAa? between alpha & gama subunits
What does Y205 stand for ? Y205 = Tyrosine (Beta Subunit)
What does F65 stand for? F65 = Phenylalenine (alpha Subunit)
What are Tyrosine & Phenylalenine responsible for in GABAa? The AA responsible for binding
How many Binding Domains on G-Protein Coupled Rcptrs "Metabotropic"? 2 binding sites on G-Pro Cpl'd Rcptrs (outside for Ligand, Inside for G-protein)
What is structure of G-protein coupled receptors? Seven transmembrane Alpha-Helices
Why is the receptor called G-Protein Coupled? G-Protein coupling domain protein is "Guanine-nucleotide bound)
What are the G-Proteins made up of? "HeteroTrimeric" = 3 subunits: alpha, beta, gama (one ea.) Alpha subunit binds to GDP, and Beta-Gama dislocate on outter membrane for other effects)
What does activation of G-Pro Cpl'd Rcptrs produce? 2nd Messengers
What type of Response rate is observed w/ G-Pro Cpl'd Rcptrs? "fast" but slower than GABAa. (sec to min)
Where aer G-Pro Cpl'd Rcptrs found? Ubiquitous: mAChR, Rcptrs of Catecholamine, Serotonin, Opioids, Peptides...
When Agonist (Hormone/N.T.) binds w/ G-Pro Cpl'd Rcptr what happens? Agonist bind on extracellular side of Membrane, Gs Protein exchanges GTP-GDP activating, Alpha-GTP subunit moves thru membrane to activate Adenylyl Cyclase, ATP converted to cAMP & PPi, Beta-Gama have other effects
what happens when Agonist is no longer attached to G-Pro Cpl'd Rcptr? Rcptr Reverts to Resting State, Alpha-GDP subunit back in place with Beta-Gama, Adenylyl Cyclase is Inactive
How many Muscarinic receptor effects ? 5 based on the types of G-Proteins they have
Can one Agonist have more than one effect? yes, by binding with different types of Muscarinic receptors
What is Amplification of signal? Cascade effect caused by G-Protein activation producing stronger effect inside cell
Albuterol is? Beta 2 Agonist Stimulating Adenylyl Cyclase to make cAMP that amplifies PKA causing protein phos. that cause bronchial muscles to relax
Bethanechol is? mAChR Agonist that activate Ca++ release via IP3 and Activated PKC by protein phos. that changes Tone of Bladder
What does Gs (G-Stimulatory) do? Activates Ca chan's & Adenylyl Cyclase (Blocked by Cholera Toxin)
What does Gi (G-Inhibitory) do? Act K+ chan's, Inhibits Adenylyl Cyclase (Blocked by Pertussis Toxin)
What does Go do? Inhibits Ca Chan's (Blocked by Pertussis Toxin)
What does Gq do? Activates Phospholipase C
What does G 12/13 do? Diverse Ion Transporter Interactions
Created by: MCPHS
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