The document discusses oxidation-reduction (redox) processes and their role in metabolism and the electron transport chain (ETC). It defines oxidation as the loss of electrons and reduction as the gain of electrons. Redox reactions are important in cellular respiration, where organisms oxidize foods through a series of metabolic reactions to generate energy in the form of ATP. The ETC involves the passage of electrons through protein complexes in the mitochondrial inner membrane, which is associated with the release of free energy used to generate ATP from ADP. Mitochondria serve as the powerhouses of cells, housing the metabolic oxidative reactions that produce reduced coenzymes utilized in the ETC to liberate energy.

1. Redox Processes
&
ETC
By
Dr Sajad Ahmad

2. Oxidation - reduction
• Oxidation is loss of electrons
• The term oxidation was originally used to
describe reactions in which an element
combines with oxygen
• Reduction is gain of electrons
• The term reduction comes from the Latin
term meaning "to lead back." Anything that
that leads back therefore involves reduction.
Oxidation is always accompanied by reduction
The total number of electrons is kept constant

3. What are oxidation and reduction?
Oxidation Reduction
addition of oxygen
e.g. 2Mg + O2  2MgO
loss of oxygen
e.g. 2CuO + C  2Cu + CO2
loss of hydrogen
e.g. CH3OH  CH2O + H2
addition of hydrogen
e.g. C2H4 + H2  C2H6
loss of electrons
e.g. Al  Al3+ + 3e-
gain of electrons
e.g. F2 + 2e-  2F-
Oxidation and reduction can be used to describe any of the following processes:

4. Changes in oxidation number
Oxidation numbers can be used to define the processes of oxidation and reduction.
oxidation
number 0 +1
H2  2H+ + 2e-
During oxidation, the oxidation number increases:
oxidation
number +3 +2
Fe3+ + e-  Fe2+
During reduction, the oxidation number decreases:

5. 5
Common uses of the terms oxidization and
reduction
Term Meaning
Oxidation To combine with oxygen
To lose hydrogen
To lose electrons
To increase in oxidation number
Reduction To lose oxygen
To combine with hydrogen
To gain electrons
To decrease in oxidation number

6. Remember this phrase: LEO the
lion says GER.
• LEO = Loss of Electrons is Oxidation
• GER = Gain of Electrons is Reduction
• Another way is to simply remember that reduction
is to reduce the oxidation number.
• Therefore, oxidation must increase the value.
• Oxidizing Agent - that substance which oxidizes
somebody else. It is reduced in the process.
• Reducing Agent - that substance which reduces
somebody else. It is oxidized in the process.

7. 7
 Oxidation-Reduction Reactions
Role in Metabolism
1. Oxidation can also be considered to be
gain of oxygen or loss of hydrogen in a
molecule.
2. Reduction can also be considered to be
loss of oxygen or gain of hydrogen in a
molecule.
3. Respiration is a redox process whereby
living organisms oxidize food to release
energy.

8. where
Ered is the half-cell reduction potential at the temperature of interest,
Eo
red is the standard half-cell reduction potential
Ecell is the cell potential (electromotive force) at the temperature of interest,
Eo
cell is the standard cell potential,
R is the universal gas constant: R = 8.314472(15) J K−1 mol−1,
T is the temperature in kelvins,
The Nernst equation for an electrochemical half-cell is

13. Electron Transport Chain
• Energy rich carbohydrates, fatty acids and
amino acids under go series of metabolic
reactions to get oxidized to CO2 and H2O
• The passage of electrons through ETC is associated
with the loss of free energy which is utilized to
generate ATP to ADP.

14. Mitochondria
• Mitochondria serves as powerhouse of the cell
• It acts as centre for metabolic oxidative reactions
to generate reduced coenzymes( NADH And
FADH2) which are utilized in ETC to liberate
energy in the form of ATP.
• Mitochondria consists of five distinct parts.
• The outer membrane
• Inner membrane
• The intermembrane space
• Cristae
• Matrix