Download Bioloical Oxidation - Home

Biologic 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.
Oxidation and Reduction
Oxidation: 1) Addition of oxygen.
2) Removal of H2
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.
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 acompound that
acts as acarrier 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 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
ATP
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
miassive energy production in the form of heat , which
it happens may destroy the living cells
AH2
B
CH2
↓
↓
↓
A
BH2
→ etc
C
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.
[Biological oxidation ]
Glucose oxidation
1- glycolysis:
it is the oxidation of glucose to give pyruvet 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