Overview of cellular energy metabolism• Electron-rich food molecules synthesized by plants are used by plants themselves, and by animals and other eukaryotes.• The electrons are removed from fuel substances, such as sugars, and donated to other molecules such as oxygen that act as electron acceptors.• In the process, some energy of the electrons is released and used to drive the synthesis of ATP.
OIL RIGOxidation and Reduction Oxidation Reduction Is Is Loss Gain• Oxidation involves the loss of electrons from an element, frequently gaining oxygen or losing hydrogen• Reduction involves a gain of electron, frequently involves losing oxygen or gaining hydrogen.
Cellular respiration includes both the reactions that transfer electrons fromorganic molecules to oxygen and the reactions the make ATP.In this overall reaction, electrons and protons are transferred from glucose tooxygen, forming water, and the carbons left after the transfer are released ascarbon dioxide.
The first series of oxidative reactions that remove electrons from cellular fuel molecules Glycolisis • Sugars such as glucose are partially oxidized and broken down into smaller molecules. • It starts with the six-carbon sugar glucose and produces two molecules of the three-carbon organic substance pyruvate in 10 sequential, ezyme-catalyzed reactions. • Pyruvate still contains many electrons that can be removed by oxidation
Glycolisis: a)Phosphorylation An energy-requiring reaction • Outline: Oxidation of Glucose (6 carbons) to two Pyruvate (3 carbons) is coupled to the reduction of ADP to ATP • Begins with phosphorylation = the adding of two phosphates • Glucose 1, 6 diphosphateThe phosphate groups allow a strongerinteraction between the hexose and its enzyme
The subsequent energy-releasing reaction Glycolisis: b)Lysis• Involves the breaking of the hexose diphosphate into two triose phosphate molecules.• The triose phosphate is an intermediate in many biochemical reactions.
The subsequent energy-releasing reaction Glycolisis: b)Lysis • Electrons are removed from the phosphorylated glucose derivatives • 4 ATP are produced, giving a net gain of 2 ATP • The removed electrons are accepted by the electron carrier molecule NAD+NAD+ = Nicotinamide Adenine Dinucleotide (NAD+ when oxidized, NADH whenreduced)
c) OxidationThe major oxidation of glycolysisremoves 2 electrons and 2 protonsfrom G3P.Both electrons and one proton (H+)are picked up by NAD+ to formNADH. The other proton is releasedinto the cytosol.Each Triose phosphate is oxidized Right before oxidation, oneto a 3 carbon molecule called other phosphate is added toPyruvate each of the G3P molecules
Each triose phosphate adds aphosphate to ADP reducing this to ATP(called substrate level phosphorylationreaction)