Biological Oxidation A.Energy is required to maintain the structure and function of the living cells. This energy is derived from oxidation of carbohydrates,lipids and proteins of diet. B.The energy liberated is partly converted into useful form ATP, which is known as energy currency of the living cells. C.Each gram of carbohydrate and protein give 4kcal upon oxidation,while each gram of fat give about 9kcal.

Respiration

Cellular Rispiration

Oxidation and Reduction Oxidation: 1) Addition of oxygen. 2) Removal of hydrogen H 3)Removal of electron from ion or atom. Reduction: 1)removal of oxygen from compound 2)addition of hydrogen 3)addition of electron. Commonly the oxidation reduction are accompanied by the reductions reactions and they are called redox reactions.

Redox reaction

Bioenergetics Difinition: Bioenergetics or thermodynamics is the study of the energy changes accompanying biochemical reactions. ATP acts as an energy carrier: The free energy made available through the catabolism of fuels (carbohydrates,lipids,amino acids)is not transmitted directly to the reaction requiring energy. Instead it is used to synthesize a compound that acts as a carrier of free energy,which is adenosine triphosphate (ATP). Free energy from fuels

Biologic work ATP is the link between energy-producing and energy consuming biologic processes. ATP Structure It is a member of a class of compounds called nucleotide triPO4 ( ATP,GTP,UTP,CTP,TTP). It has 3 component parts : abase(adenine), a sugar(ribose),and 3 phosphoryl group. That joined to ribose by a PO4 ester bonds and to each other by phospho-anhydride bonds.

ATP

ATP Structure Importance of ATP thus phospho-anhydride bond between PO4 mole 1,2, 2,3. break down PO4 mole is accompanied by a large decrease in free energy. i.e. release energy : ATP ADP + Pi AMP+PPi 7.3 K cal/mol

Break down of one energy bond of ATP give 7.3 kcal. Because ATP has a high energy bonds. It can serve as a link between energy yielding processes or exergonic reactions e.g. catabolism of glucose and fatty acids and energy requiring process or enderogenic reactions (e.g. anabolic pathways) A) catabolic reaction give energy, which can be stored in the form of ATP. B) Anabolic reactions which can utilize energy through hydrolysis of ATP. Hydrogen plays an important role in liberation of energy

in this redox reaction, H2 is oxidized while O2 is reduced and if occurs it will be accompanied by massive energy explosion. This is done in body but instead of massive energy is liberated. hydrogen must be transfers to oxygen in gradual steps. That ’ s small reactions of energy are liberated and stored for further use. Hydrogen atom is formed of one electron (e) and one proton. the removal of hydrogen atom or electron from compound by release of energy. Redox potential : (electron affinity). Oxygen has the highest electron affinity ( ↑↑↑ highest redox potential). Hydrogen has the lowest electron affinity ( ↓↓↓ lowest redox potential).

Redox potential : it is the chain of different compound of increasing redox potential between hydrogen and oxygen. The living cells depend on redox reaction for this energy requirements. The reactions started by removed of H2 from the substrate that transferred to different components of redox chain and finally to oxygen to form water.Components of redox chain have potential higher than hydrogen and lower than oxygen.. * During hydrogen (H+ and electron transfer through different components of the redox chain, energy is steps and small utilizable amounts instead of a massive energy production in the form of heat, which it happens may destroy the living cells

AH2 B CH2 A BH2 C → etc ↓ ↓ ↓ Hydrogen is transferred from A to B to C because B has higher redox potential ( electron affinity ) than A, while C has higher redox potential than B etc. in this way hydrogen ( electron + H+ ) moves from compounds of lower redox potential to compounds of higher redox potential.

During cellular respiration, most electrons travel this downhill pathway: Food NADH electron transport chain oxygen

[Biological oxidation ] Glucose oxidation 1- glycolysis: it is the oxidation of glucose to give pyruvat in the presence of oxygen or lactate in absence of O2 site : in cytoplasm of all tissues Tissues with no or little mitochondria, mature RBC, cornea, lens, retina,skeletal muscles depend mainly of glycolysis. Stage of glycolysis: 1- Energy requiring stage one molecule of glucose is converted into 2 moles of glyceraldehydes 3 - PO4 these steps requires 2 ATP (energy loss)

2-energy producing stage: a)- the 2 moles of glyceraldehydes – 3 -PO4 are converted into pyruvate (aerobic glycolysis) or lactate (anaerobic glycolysis). * steps produce ATP Energy ATP production of glycolysis. ATP production of glycolysis: ATP production = ATPproduced – ATP ultize ATP production = 4 ATP – 2 ATP = 2 ATP 4 ATP from 2 glyceradehde by sybstrate level phosphoration Oxidation of extra mitochondrial NADH+ + H+, CYtoplasmic NADH+ + H+ cannot penetrate mitochondria membrane, it can be used to produce energy ( 4 or,6 ATP) by respiratory chain phosphorylation in the mitochondria.

* this can be done by using special carrier. 2ATP + 2NADH+H 8 ATP 2ATP + 2X3 ATP 8ATP In tissue with no or little mitochondria or leak in oxygen ATP=2 only not 8