Question

For the next few questions, use these answer choices: a) Agonist b) Antagonist c) Up-regulation d) Down-regulation e) Desensitization 51) This kind of molecule binds to a receptor and blocks 52) A cell can become more responsive to a signal 53) One explanation for drug tolerance includes a loss of its activity. molecule by initiating a(n) of receptors. receptor affinity for its signal molecule, also known as 54) If levels of a signal molecule are abnormally low, a patient might be given a(n) for that signal molecule to return him or her to homeostasis.

Answer 1

1. Antagonist - these oppose or block the actionof Agonist. They act either by mimicking the structure of agonist (thus competing with agonist) or bind to Allosteric site to block it's action. They can be classified as Competitive antagonist, irreversible antagonist, physiological antagonist, chemical antagonist etc.

2.Up Regulation - In this process the cell becomes more responsive by Increasing the number of receptors (up regulation of receptor).

3. Desensitization - with prolonged stimulation the aome cell may eventually loose ability to mark response which may be due to loss of downstreaming signaling molecule or by increasing it's threshold level for activation.

4. Agonist - they mimick the action of normal physiological molecules so they help in restoring the normal level of activation of receptor.

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