Biochemistry II Lecture 04 PDF

BIOCHEMISTRY -II (UBT-310) Living cells have an analogous biological “circuit,” with a relatively reduced compound such as glucose as the source of electrons....

BIOCHEMISTRY -II (UBT-310) Living cells have an analogous biological “circuit,” with a relatively reduced compound such as glucose as the source of electrons. BIOENERGETICS As glucose is enzymatically oxidized, the released electrons flow spontaneously through a series of electron-carrier intermediates to another chemical species, such as O2. This electron flow is exergonic, because O2 has a higher affinity for electrons than do the electron-carrier intermediates. The resulting electromotive force provides energy to a variety of molecular energy transducers (enzymes and other proteins) that do biological work. Prof. Sanjai Saxena Department of Biotechnology Thapar Institute of Engineering and Technology, Patiala, Punjab 147001 INDIA Email: [email protected] ; [email protected] BIOCHEMISTRY-II Key Concepts in Redox Metabolism the two chemical species differ in their affinity for electrons, electrons flow spontaneously through the circuit, driven by a force proportional to the difference in electron affinity, the electromotive force (emf). Reduction potentials are a measurement of electron affinity. 1. Compounds with a very high affinity for electrons are oxidants, e.g., O2, and have a positive reduction potential (Eº’>0). 2. Very strong reductants are compounds that readily give up electrons, e.g., NADH, and have a negative reduction potential (Eº’