TAILIEUCHUNG - Biochemistry, 4th Edition P110

Biochemistry, 4th Edition P110. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | How Do Neurotransmission Pathways Control the Function of Sensory Systems 1053 a b FIGURE GABA y-aminobutyric acid and glycine are inhibitory neurotransmitters that activate chloride channels. Influx of Cl causes a hyperpolarization of the postsynaptic membrane. GABA receptors are similar in many respects to nicotinic acetylcholine receptors with an a2ßy8 stoichiometry. a Top view b side view. Images courtesy of Donald Weaver University of Nova Scotia and Valerie Campagna-Slater University of Toronto. H I H3N C ch2 ch2 coo- I COO- Glutamate Glutamate decarboxylase h3n ch2 ch2 ch2 coo- y-Ammobutyrate GABA GABA-glutamate transaminase Succinate O semialdehyde dehydrogenase c ch2 ch2 COO-------------------- -OOC ch2 ch2 coo- H Succinate semialdehyde Succinate FIGURE Glutamate is converted to GABA by glutamate decarboxylase. GABA is degraded by the action of GABA-glutamate transaminase and succinate semialdehyde dehydrogenase to produce succinate. been used illegally as a hallucinogenic drug under the street name of angel dust. Sadly it has caused many serious long-term psychological problems in its users. y-Aminobutyric Acid and Glycine Are Inhibitory Neurotransmitters Certain neurotransmitters acting through their conjugate postsynaptic receptors inhibit the postsynaptic neuron from propagating nerve impulses from other neurons. Two such inhibitory neurotransmitters are y-aminobutyric acid GABA and glycine. These agents make postsynaptic membranes permeable to chloride ions and cause a net influx of Cl which in turn causes hyperpolarization of the postsynaptic membrane making the membrane potential more negative . Hyperpolarization of a neuron effectively raises the threshold for the onset of action potentials in that neuron making the neuron resistant to stimulation by excitatory neurotransmitters. These effects are mediated by the GABA and glycine receptors which are ligand-gated chloride channels Figure . GABA is derived by a decarboxylation

• Sinh học
• Nền tảng của hóa sinh học
• trao đổi chất protein
• RNA trao đổi chất
• nguyên tắc của hóa sinh
• Axit amin
• công nghệ DNA