Oxidation and reduction processes in metabolism

1. OXIDATION REDUCTION
(REDOX REACTIONS)
Group members name
Maryam khan
Huba siddiqui
Maryam abdul khaliq
Ayesha noor

2. Q: What is oxidation and reduction?
• Oxidation and reduction, often referred to together as redox reactions, are fundamental
processes in chemistry that involve the transfer of electrons between atoms.
• Oxidation:
• Loss of electrons: During oxidation, an atom or molecule loses one or more electrons.
• Increase in oxidation number: Oxidation is assigned an increase in oxidation number.
Oxidation numbers are hypothetical charges assigned to atoms to keep track of electron
transfers in a reaction.
• Examples:
• A metal atom losing electrons to form a positively charged ion (e.g., iron (Fe) rusting).
• A molecule losing an oxygen atom (O) and gaining a double bond (e.g., ethanol burning in
oxygen).
• Reduction:
• Gain of electrons: Conversely, reduction involves a gain of electrons by an atom or molecule.
• Decrease in oxidation number: Reducti: Reduction is assigned a decrease in oxidation
number.
• Examples:
• A non-metal atom gaining electrons to form a negatively charged ion (e.g., chlorine (Cl)
gaining an electron to become chloride (Cl-)).
• A molecule gaining a hydrogen atom (H) and losing a double bond (e.g., converting a ketone
to an alcohol).

3. REDOX REACTION
• Coupled processes: Oxidation and reduction always occur
simultaneously. The electrons lost in oxidation are gained in
reduction. They cannot happen independently.
• Redox agents: The species causing oxidation is called the
oxidizing agent, and the one causing reduction is the reducing
agent

4. Types of redox reaction
• Redox reactions come in various flavors, each with its own
characteristics. Here's a breakdown of the five main types of redox
reactions:
•
• 1. Combination Reactions:
•
• Description: Two or more elements or simple compounds combine
to form a single, more complex compound.
• Redox aspect: This can be a redox reaction only if at least one of the
starting elements is in its free (uncombined) state. In this case, the
element that loses electrons (goes from a free state to a combined
state) undergoes oxidation.
• Example:
• Reactants: 2H2(g) + O2(g) → 2H2O(l)
• Analysis: Hydrogen (H) goes from a free element (H2) to a
combined state (H2O), losing electrons (oxidation). Oxygen (O2)
remains unchanged.

5. DECOMPOSITION REACTION
Description: A single compound breaks down into two or more simpler substances.
Redox aspect: Not inherently redox. However, if the decomposition involves a change in
oxidation state for an element, it becomes a redox reaction.
Example (Non-redox):
Reactants: CaCO3(s) → CaO(s) + CO2(g)
Analysis: No change in oxidation states for Ca or C.
3. Displacement Reactions:
Description: A more reactive element replaces a less reactive element in a compound. This
can happen for metals or non-metals.
Redox aspect: Redox because the more reactive element displaces the less reactive one by
gaining electrons (reduction), while the less reactive element loses electrons (oxidation).
Subcategories:
Metal Displacement: A more reactive metal displaces a less reactive metal from a salt
solution.
Example: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
Analysis: Iron (Fe) displaces copper (Cu) by gaining electrons (reduction). Cu loses
electrons (oxidation).
Non-metal Displacement: A more reactive non-metal displaces a less reactive non-metal
from a compound. This is less common than metal displacement.
Example: Cl2(g) + 2KI(aq) → 2KCl(aq) + I2(s)
Analysis: Chlorine (Cl) displ

6. 4. Disproportionation Reaction:
Description: A single element in a compound undergoes both oxidation and reduction
simultaneously to form two different products.
Redox aspect: The element changes its oxidation state in two ways, with one part
being oxidized and another part being reduced.
Example:
Reactants: 2ClO⁻(aq) + 2H⁺(aq) → ClO₃⁻(aq) + Cl⁻(aq) + H₂O(l)
Analysis: Chlorine (Cl) in ClO⁻ undergoes both reduction (forming Cl⁻) and oxidation
(forming ClO₃⁻
5. Comproportionation Reaction:
Description: The opposite of disproportionation. Two atoms of the same element in
different oxidation states combine to form a newcompound with an intermediate
oxidation state.
Redox aspect: Both elements undergo a change in oxidation state, but in opposite
directions, to reach a common intermediate state.

7. Example:
Reactants: NO(g) + NO₂(g) → NO₂(g) (dimerization)
Analysis: Nitrogen (N) in NO is oxidized (gains oxygen) while N in NO₂ is reduced (loses oxygen).
Both reach the same +2 oxidation state in the NO₂ dimer product.
Key Points to Remember:
Not all combination or decomposition reactions are redox reactions. Identify changes in oxidation
states to confirm redox.
Displacement reactions involve a transfer of electrons between elements of differing reactivity.
Disproportionation and comproportionation involve the same element undergoing redox changes
within a single reaction.
By understanding these different types of redox reactions, you can better analyze and predict the
behavior of elements and compounds in various chemical scenarios.

8. APPLICATIONS OF REDOX REACTIONS
• Redox reactions are used in many different applications. One application is
in the manufacturing of explosives. Redox reactions are used to create the
explosive compounds. Another application is in the manufacturing of
batteries. Redox reactions are used to create the cells in a battery.
• Redox reactions are a type of chemical reaction in which electrons are
transferred between molecules. In a redox reaction, one molecule donates
electrons to another molecule, and the second molecule accepts the
electrons. These electron transfers can result in the formation of new
molecules, or in the alteration of the oxidation state of atoms in a
molecule.
• Redox reactions are important in many different applications. One major
application of redox reactions is in the production of fuels. In fuel
production, redox reactions are used to convert simple molecules into
more complex molecules that can be used as fuel. For example, in the
production of ethanol, redox reactions are used to convert glucose into
ethanol.

9. • Redox reactions are also important in the production of metals. In metal
production, redox reactions are used to convert metal ores into metal. For
example, in the production of copper, redox reactions are used to convert copper
ore into copper.
• Redox reactions are also used in the production of many different types of
chemicals. In chemical production, redox reactions are used to convert simple
molecules into more complex molecules that can be used in products such as
plastics and pharmaceuticals. For example, in the production of plastics, redox
reactions are used to convert crude oil into different types of plastics.
• Redox reactions are also used in the treatment of wastewater. In wastewater
treatment, redox reactions are used to convert pollutants into harmless molecules.
For example, in the treatment of wastewater, redox reactions are used to convert
ammonia into nitrogen gas.
• Redox reactions are vital in biological processes like photosynthesis (conversion of
carbon dioxide and water into glucose and oxygen) and respiration (breakdown of
glucose to produce energy).

10. EXAMPLES
CELLULAR RESPIRATION
• Cellular Respiration:
• Cellular respiration is the process by which cells break down glucose
and other organic molecules to produce ATP (adenosine
triphosphate), the primary energy currency of cells. It occurs in
multiple stages:
• a. Glycolysis:
• Glycolysis occurs in the cytoplasm and involves the breakdown of
glucose (a 6-carbon molecule) into two molecules of pyruvate (a 3-
carbon molecule).
• During glycolysis, glucose is oxidized to produce two molecules of
NADH (reduced form of NAD+) and a net gain of two molecules of
ATP.
• Glycolysis does not directly require oxygen and is the initial step of
both aerobic and anaerobic respiration.

11. Pyruvate Decarboxylation:
• In the presence of oxygen, pyruvate molecules
produced by glycolysis enter the
mitochondria.
• Each pyruvate molecule is converted into
acetyl-CoA through a decarboxylation
reaction, releasing CO2 and producing NADH.

12. Citric Acid Cycle (Krebs Cycle):
• Acetyl-CoA enters the citric acid cycle, a series
of enzyme-catalyzed reactions that occur in
the mitochondrial matrix.
• During the cycle, acetyl-CoA is oxidized,
leading to the production of NADH and FADH2
(reduced forms of NAD+ and FAD,
respectively), ATP, and co2.

13. d. Electron Transport Chain (ETC):
• The NADH and FADH2 generated in glycolysis, pyruvate
decarboxylation, and the citric acid cycle donate their electrons to
the electron transport chain.
• The ETC consists of a series of protein complexes embedded in the
inner mitochondrial membrane.
• As electrons move through the ETC, energy is released and used to
pump protons (H+) across the inner mitochondrial membrane,
creating a proton gradient.
• The final electron acceptor in the ETC is oxygen, which combines
with protons to form water.
• The flow of protons back into the mitochondrial matrix through ATP
synthase drives the synthesis of ATP in a process called
chemiosmosis.
• Overall, cellular respiration generates ATP through the oxidation of
glucose and other organic molecules, with oxygen serving as the
final electron acceptor in aerobic respiration.

14. Cellular respiration cycle