ELECTRON TRANSPORT CHAIN OF BACTERIA.pptx

The NADH and FADH2 formed in glycolysis, TCA cycle and fatty acid oxidation are energy-rich molecules because they contain a pair of electrons that have high transfer potential.
ATP is generated as a result of the energy produced when electrons from NADH and FADH2 are passed to molecular oxygen by a series of electron carriers, collectively known as the electron transport chain (ETC).
The electron transport chain is also called the Cytochrome oxidase system or as the Respiratory chain.
The electron transport chains of bacteria (prokaryotes) operate in plasma membrane (mitochondria are absent in prokaryotes).
In bacteria, the protons are transported from the cytoplasm of the bacterium across the cytoplasmic membrane to the periplasmic space located between the cytoplasmic membrane and the cell wall .

NADH (NADH is the electron donor) to acceptors and moves protons (H+) across the plasma membrane similar to mitochondrial electron transport chain, it is quite different from the latter in its construction.
E. coli transport chain is short, consists of two branches (cytochrome d branch and cytochrome o branch), and a quite different array of cytochromes (e.g., Cyt b558, Cytb562, Cyt d, Cyt o).
Coenzyme Q (ubiquinone) carries electrons and donates them to both branches, but the branches operate under different growth conditions.
The cytochrome d branch shows very high affinity for oxygen and operates at low oxygen levels (low aeration) usually when the bacterium is in stationary phase of growth.
This branch is not as efficient as the cytochrome o branch because it does not actively pump protons to periplasmic space.
The cytochrome o branch shows moderately high efficiency for oxygen and operates at high oxygen concentrations (high aeration). This branch operates normally when the bacterium is in log phase of its growth (i.e., growing rapidly), and actively pumps protons (H+) in the periplasmic space.

COMPONENTS OF ETS OF BACTERIA
ELECTRON DONOR
Bacteria can use a number of different electron donors, like NADH or succinate
QUINONE CARRIERS
Bacteria use ubiquinone (the same quinone that mitochondria use) and related quinones such as menaquinone.
PROTON PUMPS
Most oxidases and reductases are proton pumps, but some are not. Cytochrome bc1 is a proton pump found in many, but not all, bacteria (it is not found in E. coli).
CYTOCHROME ELECTRON. CARRIERS

COMPARISON BETWEEN BACTERIAL AND MITOCHONDRIAL ETS

The electron transport chains of bacteria (prokaryotes) operate in plasma membrane. In eukaryotes it occurs in the inner mitochondrial membrane.
Uses different variety of electron acceptor substances, the bacterial electron transport chains are frequently very different.
Bacterial electron transport chains vary in their electron carriers (e.g., in their cytochromes) and are usually extensively branched.
Electrons often enter at several points and leave through several terminal oxidases.

CONCLUSION
Electron transport chains in bacteria are branched

1. ETS OF BACTERIA (RESPIRATION)

2. INTRODUCTION The NADH and FADH 2  formed in  glycolysis ,  TCA cycle   and fatty acid oxidation are energy-rich molecules because they contain a pair of electrons that have high transfer potential. ATP is generated as a result of the energy produced when electrons from NADH and FADH 2  are passed to molecular oxygen by a series of electron carriers, collectively known as the electron transport chain (ETC). The electron transport chain is also called the Cytochrome oxidase system or as the Respiratory chain. The electron transport chains of bacteria (prokaryotes) operate in plasma membrane (mitochondria are absent in prokaryotes). In bacteria, the protons are transported from the cytoplasm of the bacterium across the cytoplasmic membrane to the periplasmic space located between the cytoplasmic membrane and the cell wall .

3. COMPONENTS OF ETS OF BACTERIA

4. Electron transport chain of E scherichia coli

5. Electron transport chain of E scherichia coli NADH (NADH is the electron donor) to acceptors and moves protons (H + ) across the plasma membrane similar to mitochondrial electron transport chain, it is quite different from the latter in its construction. E. coli transport chain is short, consists of two branches (cytochrome d branch and cytochrome o branch), and a quite different array of cytochromes (e.g., Cyt b 558 , Cytb 562 , Cyt d, Cyt o). Coenzyme Q (ubiquinone) carries electrons and donates them to both branches, but the branches operate under different growth conditions. The cytochrome d branch shows very high affinity for oxygen and operates at low oxygen levels (low aeration) usually when the bacterium is in stationary phase of growth. This branch is not as efficient as the cytochrome o branch because it does not actively pump protons to periplasmic space. The cytochrome o branch shows moderately high efficiency for oxygen and operates at high oxygen concentrations (high aeration). This branch operates normally when the bacterium is in log phase of its growth (i.e., growing rapidly), and actively pumps protons (H + ) in the periplasmic space.

6. Electron transport chain of P aracoccus denitrificans Paracoccus denitrificans is a gram-negative, facultative anaerobic soil bacterium. It is a model prokaryote for studies of respiration.

7. But, when this bacterium grows anaerobically with nitrate as its electron acceptor , the chain is structured quite differently.

8. COMPARISON BETWEEN BACTERIAL AND MITOCHONDRIAL ETS The electron transport chains of bacteria (prokaryotes) operate in plasma membrane . In eukaryotes it occurs in the inner mitochondrial membrane. Uses different variety of electron acceptor substances , the bacterial electron transport chains are frequently very different. Bacterial electron transport chains vary in their electron carriers (e.g., in their cytochromes) and are usually extensively branched. Electrons often enter at several points and leave through several terminal oxidases. Bacterial electron transport chains are usually shorter and possess lower phosphorus to oxygen (P/O) ratios than mitochondrial transport chain. CONCLUSION Electron transport chains in bacteria are branched, modular, and inducible.