Chapter 26 biosynthesis of membrane lipids and steroids

Because three Na+ ions move outward for every two K+ ions that move inward, the process is electrogenic-it creates a net separation of charge across the membrane, making the inside of the cell negative relative to the outside. The resulting transmembrane potential of -50 to -70 mV (inside negative relative to outside) is essential to the conduction of action potentials in neurons, and is also characteristic of most nonneuronal animal cells. The activity of this Na+K+ ATPase in extruding Na+ and accumulating K+ is an essential cell functiom about 25% of the energy-yielding metabolism of a human at rest goes to support the Na+K+ ATPase.

The NH proton in pyrroles is moderately acidic with a p K a of . Pyrrole can be deprotonated with strong bases such as butyllithium and sodium hydride . The resulting alkali pyrrolide is nucleophilic . Treating this conjugate base with an electrophile such as iodomethane gives N -methylpyrrole. N -Metalated pyrrole can react with electrophiles at the N or C positions, depending on the coordinating metal. More ionic nitrogen–metal bonds (such as with Li, Na, and K) and more solvating solvents lead to N -alkylation. Nitrophilic metals, such as MgX, lead to alkylation at C (mainly C2), due to a higher degree of coordination to the nitrogen atom. In the cases of N -substituted pyrroles, metalation of the carbons is more facile. Alkyl groups can be introduced as electrophiles, or by cross-coupling reactions. [ citation needed ]

Chapter 26 biosynthesis of membrane lipids and steroids

chapter 26 biosynthesis of membrane lipids and steroids

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