the enzymatic oxidation of fuel molecules by molecular oxygen; includes aerobic and anaerobic but often used to refer to aerobic
Electrons from organic compounds (in the form of hydrogen atoms) are not transferred directly to O₂, but instead are usually first transferred to an electron carrier, a coenzyme
-accepts hydrogens and electrons in the oxidation reactions of catabolism
the reduced form of NAD⁺
-Represents stored energy that is tapped to synthesize ATP
How does NAD⁺ trap electrons from glucose and other organic molecules?
Enzymes called dehydrogenases remove a pair of hydrogen atoms (2 electrons and 2 protons) from the substrate (glucose), thereby oxidizing it.
The enzyme then delivers the 2 electrons along with only one hydrogen proton to NAD+. The other proton is released as a hydrogen ion (H+) into the surrounding solution
By receiving 2 negatively charged electrons but only one positively charged proton, NAD+ has its charge neutralized when it is reduced to NADH.
The name NADH shows that a hydrogen has been received in the reaction.
NAD+ is the most versatile electron acceptor in cellular respiration and functions in several of the redox steps during the breakdown of glucose.
How do electrons that are extracted from glucose and stored as potential energy in NADH finally reach oxygen?
-NADH passes the electrons to the electron transport chain.
-Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction.
-O2 pulls electrons down the chain in an energy-yielding tumble.
-The energy yielded is used to generate ATP
occurs in the cell cytoplasm and breaks down glucose into two molecules of pyruvate
transported into the mitochondrion and then is broken down to an acetyl group
Citric acid cycle
occurs in the mitochondrial matrix and completes the breakdown of glucose by oxidizing a derivative of pyruvate to CO2
powered by the redox reactions of the electron transport chain and accounts for most (90%) of the ATP synthesis generated by cellular respiration
3 phases of Glycolysis
--2 ATP hydrolyzed to create fructose- 1,6 bisphosphate
--6 carbon molecule broken into two 3
carbon molecules of glyceraldehyde-3-
molecules broken down into two
pyruvate molecules producing 2 NADH
and 4 ATP