0.20 Bis2a 06.0 energy in living systems v1.2  (Page 6/15)

Oxidative phosphorylation

While we will discuss this in detail later, in essence oxidative phosphorylation works by taking a reduced high energy compound, such as NADH+H+ or FADH2, and transferring electrons in a series of redox reactions to other compounds. The energy that is release is then "captured" by the translocation of protons (H+) across the membrane. The net result is an "energize membrand" that separates charge, negative on the inside and positive on the outside (the electrical potential) and the separation of protons (chemical potential), protons concentration greater on the outside then inside of the membrane. The overall energized state of the membrane is then similar to a charged capacitor ready to do work. ATP generation occurs by the F0F1 membrane bound ATPase that translocates protons across the membrane discharging the chemical and electrical potentials with the simultaneous synthesis of ATP. For every three protons (H+) translocated, the F0F1ATPase can synthesize 1 ATP.

Finally, oxidative phosphorylation does NOT require oxygen to function. The word oxidative in this case is in reference to redox reactions driving the process. We are very familiar with aerobic respiration which uses molecular oxygen as the terminal electron acceptor in some electron transport chains but this is a subset of reactions. As we will see later, other electron transport chains can use other compounds besides molecular oxygen as a terminal electron acceptor, such as nitrate or nitrite.

Photophosphorylation

While we will discuss this in detail later, in essence oxidative phosphorylation works by taking a reduced high energy compound, such as NADH or FADH2, and transferring electrons in a series of red/ox reactions to other compounds. The energy that is release is then "captured" by the translocation of protons (H+) across the membrane. The net result is an "energize membrane" that separates charge, negative on the inside and positive on the outside (the electrical potential) and the separation of protons (chemical potential), protons concentration greater on the outside then inside of the membrane. The overall energized state of the membrane is then similar to a charged capacitor ready to do work. ATP generation occurs by the F0F1 membrane bound ATPase that translocates protons across the membrane discharging the chemical and electrical potentials with the simultaneous synthesis of ATP. For every three protons (H+) translocated, the F0F1ATPase can synthesize 1 ATP.

Section summary

ATP functions as the energy currency for cells. It allows the cell to store energy briefly and transport it within the cell to support endergonic chemical reactions. The structure of ATP is that of an RNA nucleotide with three phosphates attached. As ATP is used for energy, a phosphate group or two are detached, and either ADP or AMP is produced. Energy derived from glucose catabolism is used to convert ADP into ATP. When ATP is used in a reaction, the third phosphate is temporarily attached to a substrate in a process called phosphorylation. The two processes of ATP regeneration that are used in conjunction with glucose catabolism are substrate-level phosphorylation and oxidative phosphorylation through the process of chemiosmosis.

Additional links

Chemwiki links

• ATP

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