19. Substances A and B have affinity for the same receptor but substance B is a full agonist whereas A lacksefficacy. When co-administered with A, the efficacy of B is reduced and remains the same when the doseof B is doubled. What type of ligand is substance A?a) Partial agonistb) Inverse agonistc) Non-competitive antagonistd) Competitive antagoniste) Positive allosteric modulator

Competitive Antagonism Mechanism:1. Binding Site Competition- A competitive antagonist binds to the…

Answered: 19. Substances A and B have affinity…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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21. GABA, benzodiazepines and barbituates share a common receptor target and elicit similar pharmacodynamic responses yet are susceptible to different antagonists. Which property or process best explains this observation? a) The three molecules target different sub-types of the receptor b) The three molecules are different types of ligands (e.g. full, partial, inverse agonists) c) The three molecules have affinity for distinct binding sites on the receptor d) The three molecules activate different G-proteins e) The three molecules interact with different repressor proteins
8. Select the correct definition of agonist and antagonist: a) An agonist activates the receptor. An antagonist produces an effect opposite to that of an agonist. b) An agonist partially activates the receptor. An antagonist blocks activation of the receptor. c) An agonist partially activates the receptor. An antagonist produces an effect opposite to that of an agonist. d) An agonist activates the receptor. An antagonist blocks activation of the receptor.
30. What do the pharmacodynamic mechanisms of the following four compounds share in common? Antihistamines Compoun Caffeine Naloxone a) They all reduce receptor activation by endogenous agonists b) They are all receptor antagonists c) They all bind to ion channels d) They all inhibit enzyme function e) They all activate transcription Propranolol
1) A drug that binds at the same site as the neurotransmitter and prevents the neurotransmitter from opening ion channels would be termed a(n) a) direct antagonist b) direct agonist c) indirect agonist d) indirect antagonist 2) A drug that binds at a site different from that of the neurotransmitter and opens ion channels would be termed a(n) a) direct antagonist b) direct agonist c) indirect agonist d) indirect antagonist
22. Xenobiotics Y & Z are agonists for a G-protein coupled receptor and tyrosine kinase receptor, rerspectively. When combined, cross-talk between activated signaling pathways can lead to which of the following types of interaction? a) Additive effects b) Antagonistic effects c) Synergistic effects d) b & c e) all of the above
1. Ionotropic GABA receptors are ligand-gated Cl channels which open during GABA-ergic signaling. a) Describe how under normal circumstances the opening of these channels leads to an IPSP. Do this in the context of Eci. b) Some cells in the body express a Na*/K+/2Cl cotransporter which pumps Cl- into the ICF. Where these pumps are present, the same GABA receptor is actually excitatory. Again, in the context of Ea describe how the same receptor would be excitatory in cells which actively pump Cl- into the ICF. You do not need to repeat information you provided in part (a)
1)The concept of saturation is defined as? a) The ability of a receptor to bind only one type or a limited number of structurally related types of chemical messengers. b) The degree to which receptors are occupied by messengers. c) A decrease in the total number of target-cell receptors for a given messenger d) The increased responsiveness of a target cell to a given messenger 2. Phosphodiesterase activity produces one of the following actions a) Breakdown cAMP b) Increases cAMP c) Increases PKC activity d) Increases cytosolic IP3 levels 3. Phospholipase C leads to one of the following? a) Increase in cAMP b) Breakdown of cAMP c) Increase in cytosolic levels of IP3 and DAG d) A decrease in cytosolic Ca++ concentration
7. Organophosphates, which are found in a lot of insecticides, block the activity of acetylcholineesterase. What might be a result of blocking this important enzyme? A)Hyperstimulation of the nicotinic receptor B)Accelerated ACh breakdown in the synaptic cleft C)Muscle paralysis due to limited activity in the muscle cell
9. If you were to compare an agonist bound receptor and an antagonist bound receptor Which of the following statements is common to all receptors? a) A channel opens when activated b) There is a conformational change when activated c) The receptor is dimerized when activated d) There are no structural differences 10. Most xenobiotics act transiently and therefore interact with their receptor through weak interactions. Which type of interaction would you not expect to see when examining the receptor ligand interactions for an uncharacterized xenobiotic? a) Van der Waals interactions b) Hydrogen bonds c) Hydrophobic interactions d) All of the above e) None of the above 11. Name the interaction the arrow is pointing to (image to the right): a) Hydrogen Bond b) Pi stacking c) Cation-pi interaction d) Electrostatic interaction H-O 0 NH3 -H 12. Non-competitive antagonists share which of the following characteristics with non-competitive enzyme inhibitors? a) Bind covalently with target…
13. Flumazenil is the antidote for benzodiazepine overdose, acting as a competitive antagonist at GABAa receptors in the CNS. The effective dose of flumazenil to treat overdose thus depends on which of the following benzodiazepine properties? a) Intrinsic activity and dose b) Receptor affinity and dose c) Selectivity and intrinsic activity d) Selectivity and receptor affinity e) Selectivity and dose
34. A 32-year-old woman has had progressive intermittent double vision for the past 6 weeks and weakness in her legs for the past 2 weeks. Physical examination shows bilateral ptosis and normal sensory function in her legs. The most likely mechanism of these findings is antibody to which of the following? OA) Acetylcholine receptor B) Cholinesterase C) Motor end-plate membrane D) Myosin E) Postsynaptic membrane
Beta-blockers are used to treat cardiovascular disorders because they are antagonists at beta-adrenergic receptors. Within the cell this activity will be seen as? OA) Increased signaling via the G₁ protein B) Increased protein kinase A activity Decreased phospholipase C activity D) Decreased cAMP levels E) Increased inositol 1,4,5-trisphosphate levels

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