LITTLE ABOUT LESOTHO FROM THE TIME MOSHOESHOE THE FIRST WAS BORN
Botany_203_ppt[1].pptx
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3. Step 5: Succinyl CoA is then converted to succinate (4 carbon molecule) and one
GTP molecule is produced.
Step 6: Succinate is converted into fumarate (4 carbon molecule)and a molecule of
FADH, is produced.
Step 7: Fumarate is converted to malate (another 4 carbon molecule)
Step 8: Malate is then converted into oxaloacetate and NADH is also produced here.
4. Electorn transport chain
Introduction
The electron transport chain is a cluster of proteins that transfer electrons through a
membrane within mitochondria to form a gradient of protons that drives the creation of
adenosine triphosphate (ATP).
ATP is used by the cell as the energy for metabolic processes for cellular functions.
5. Where Does the Electron Transport Chain
Occur?
During the process, a proton gradient is created when the protons are pumped from the
mitochondrial matrix into the intermembrane space of the cell, which also helps in
driving ATP production.
Often, the use of a proton gradient is referred to as the chemiosmotic mechanism that
drives ATP synthesis since it relies on a higher concentration of protons to generate
“proton motive force”.
The amount of ATP created is directly proportional to the number of protons that are
pumped across the inner mitochondrial membrane.
6. Electorn transport chain
Respiratory chain :
In the Krebs cycle NADH and H are produced from NAD”. NADH then transfers the
hydrogen atom to the respiratory chain (also called electron transport system) where
electrons are transported in a series of oxidation-reduction steps to react, ultimately, with
molecular oxygen.
The oxidation reduction substances which take part in respiratory chain are:
A coenzyme called coenzyme Q
A series of cytochrome enzymes (b,c,a,a3)
Molecular oxygen (O²)
Cytochromes are electron transport intermediates containing haem of related prosthetic
groups, that undergo valency changes of iron atom. Haem is the same iron containing group
that is oxygen carrying pigment in haemoglobin. The path of electrons in the respiratory
chain appears to be as follows.
8. Steps
Step 1:NADH is oxidized by coenzyme Q. This oxidation yields enough free energy to
permit the synthesis of a molecule of ATP from ADP and inorganic phosphate.
Step 2:Coenzyme Q is in turn oxidized by cytochrome b which is then oxidized by
cytochrome c. This step also yields enough energy to permit the synthesis of a molecule
of ATP.
Step 3:Cytochrome c then reduces a complex of two enzymes called cytochrome a and
as (for convenience the complex is referred as cytochrome a).
Step4: Cytochrome a is oxidized by an atom of oxygen and the electrons arrive at the
bottom end of the respiratory chain.
Step 5: Oxygen is the most electronegative substance and the final acceptor of the
electrons. A molecule of water is produced. In addition, this final oxidation provides
enough energy for the synthesis of a third molecule of ATP.
9. Oxidative Phosphorylation
Oxidative phosphorylation is the process of ATP formation, when electrons are
transferred by electron carriers from NADH or FADH2 to oxygen”.
Oxidative phosphorylation is the final step in cellular respiration. It occurs in
the mitochondria. It is linked to a process known as electron transport chain.
The electron transport system is located in the inner mitochondrial
membrane. The electrons are transferred from one member of the transport
chain to another through a series of redox reactions.
10.
11. Steps in Oxidative Phosphorylation
Delivery of Electrons by NADH and FADH2
Electron Transport and Proton Pumping
Splitting of Oxygen to form Water
ATP Synthesis
Chemiosmosis
12. Delivery of Electrons by NADH and
FADH2
Reduced NADH and FADH2 transfer their electrons to molecules near the beginning
of the transport chain. After transferring the electrons, they get oxidised to NAD+ and
FAD and are utilised in other steps of cellular respiration.
13. Electron Transport and Proton Pumping
The electrons move from a higher energy level to a lower energy level, thereby
releasing energy. Some of the energy is used to move the electrons from the matrix to
the intermembrane space. Thus, an electrochemical gradient is established.
14. Splitting of Oxygen to form Water
The electrons are then transferred to the oxygen molecule which splits into
half and uptakes H+ to form water.
15. ATP Synthesis
ATP SynthesisThe H+ ions pass through an enzyme called ATP synthase while flowing
back into the matrix. This controls the flow of protons to synthesize ATP.
16. Chemiosmosis
Oxidative phosphorylation uses the chemical reactions that release energy to drive a
chemical reaction that requires energy. These 2 sets of reactions are coupled and
interrelated.
The electrons that flow through electron transport chain is an exergonic process and the
synthesis of ATP is an endergonic process. These two processes are ingrained within a
membrane. As a result, energy will be transmitted from the electron transport chain to
ATP synthase by the movement of proteins. This process is termed as chemiosmosis.
Endergonic Process is a chemical reaction in which energy is absorbed. There will be a
change in free energy and it is always positive. Exergonic Process is a chemical
reaction in which there will be a positive flow of energy from the system to the
surrounding environment. Chemical reactions are also considered exergonic when they
are spontaneous.
