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9 Cards in this Set
- Front
- Back
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What is the difference between competitive and noncompetitive inhibitors |
Competitive inhibitors are ligands that bind to the same active,catalytic site as with endogenous substrate. Noncompetitive inhibitors are ligands that binds to a different site on the enzyme and alter the shape of the molecule and thereby reducing its catalytic activity |
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What are stereoisomers? |
Molecules with the same molecular formula but different arrangement of atoms in 3d spaces |
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Explain what G-protein coupled receptors are and discuss signal transduction in G-protein receptors |
G-protein couples receptors are the largest family of receptors for pharmaceutical agents. The extracellular and to some extent the transmembrane determines the ligand binding and its selectivity. The intracellular domain mediates the receptor interaction with its effector molecule
G-protein consists of an alpha, beta and gamma subunits. When the cell is inactive. The alpha subunit binds the GDP molecule. When the ligands binds the extracellular domain, it cause the G-protein to change its shape, thus triggering the alpha subunit to release the GDP to bind the GTP. This causes the alpha subunit to detach and trigger other proteins in the signaling pathway. |
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Explain what the tyrosine kinase are, what types of ligand activates these receptors and how do they change the activity of specific enzymes cascade |
Tyrosine kinase are enzymes that can transfer phosphate group from ATP to tyrosine residues of specific proteins in the cell.
The types of ligands that activates these receptors are epidermal growth factor, nerve growth factor and insulin
Before a ligand binds on the tyrosine receptor binding site..the polypeptides exists as individuals structures. However, as soon as the ligand binds the binding site, it causes the receptor to aggregate, to form a complex called a dimer through a process known as dimerization. This dimer is unphosphorylated but the tyrosine region are activated. The phosphorylation of the dimer is achieved by the kinase activity of the receptor which transfer phosphorus from ATP to the tyrosine kinase itself. This makes the dimer to become phosphorylated. The phosphorylation dimer triggers relay proteins to bind on the phosphorylated region of the tyrosine and they undergo conformational change. This activated relay protein triggers a transduction pathway, thus leading to a cellular response. |
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Describe how type 1 nuclear receptors are activated |
The type 1 nuclear receptors are located inside the cell and are bound to accessory heat shock protein. They are activated when the steroids diffuse through the cell membrane, to bind on the binding site. On activation, heat shock protein dissociate an the two steroid receptor protein dimerize and translocate to the nucleus. They then binds to specific DNA sequence of genes and initiates transcription. |
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Define the agonist, antagonists, efficacy and affinity. |
Agonist: drugs that binds to a receptor and activates the receptor. Antagonist: drugs to a receptor but doesn't activate it. It binds to the receptor to stop the agonist from binding Affinity: is the tendency of a drug to bind its receptor. Efficacy- tendency of a drug to activate its receptor. |
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What is the difference between a competitive antagonist and a noncompetitive antagonist |
Competitive antagonist binds to the same binding site as the agonist but are reversibly bound. Noncompetitive antagonist blocks the agonist irreversibly by forming covalent bonds |
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Describe how tolerance occurs at a cellular level? |
The continuous and repeated exposure to agonist can desensitize receptors, usually by phosphorylating the serine or threonine residues in the c-terminal domain of the GPCR Phosphorylation of the receptors reduces the G protein coupling efficiency and binding affinity. Phosphorylation also signals the cell to internalize the membrane receptors. Through internalization and regulation of the receptor genes, the number of receptors decreases. Disease states can also alter the number and function of receptors |
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Under what conditions may the receptor be up regulated and under what conditions may the receptors be down regulated? |
Continuous exposure to agonist leads to down regulation Continuous exposure to antagonist leads to up regulation. |
