NAD+ and FAD with dehydrogenases

Coenzymes and Electron Shuttles

• Coenzymes: NAD+ and FAD are examples, functioning as electron shuttles in cellular processes.

• Role of Electron Shuttles:

  • Pick up electrons from one location in the cell.

  • Deliver electrons through the electron transport chain (ETC).

  • After delivering, they return to pick up more electrons.

Dehydrogenases

• Definition: Enzymes that catalyze the transfer of hydrogen atoms from one molecule to another.

  • Dehydrogenases facilitate dehydrogenation (removal of hydrogen, where "de-" means removal and "hydrogenation" refers to the addition of hydrogen).

• Chemical Components of Hydrogen:

  • Each hydrogen atom (H) consists of one proton (H⁺) and one electron.

Mechanism of Dehydrogenases

• Binding with NAD⁺:

  • Dehydrogenase binds with NAD⁺ (an energy-rich molecule) that has two hydrogen atoms.

  • Removing two protons and two electrons leads to the conversion of NAD⁺ to NADH:

    • 2 protons (2 H⁺) and 2 electrons are transferred;

    • Only one proton is transferred to NAD⁺, reducing it to NADH.

• Oxidation-Reduction:

  • As NAD⁺ is reduced to NADH, the energy-rich molecule is oxidized (loses hydrogen).

  • A proton is released into the solution.

Electron Transport Chain (ETC)

• Location: The electron transport chain occurs in the inner mitochondrial membrane.

• Function: NADH (carries 2 electrons and 1 proton) and FADH₂ (also carries 2 electrons and 2 protons) deliver electrons to the ETC.

FAD and FADH₂

• FAD to FADH₂ Conversion:

  • FAD accepts two protons and two electrons from the energy-rich molecule, becoming FADH₂.

• Difference Between NADH and FADH₂:

  • Both carry two electrons to the ETC.

  • NADH carries one proton, while FADH₂ carries two protons.

Summary of Key Points

• Enzymatic Requirement:

  • Dehydrogenases are essential for converting NAD⁺ to NADH and FAD to FADH₂.

• Forms of Coenzymes:

  • NAD⁺ and FAD are the oxidized forms of NADH and FADH₂, respectively.

  • Remember the distinctions in the number of protons each carries and their roles in the electron transport chain.