Textbook Question
What nutritional type is a colorless microbe that uses the Calvin-Benson cycle, uses H₂ as the electron donor to its ETC, and uses elemental S as the final electron acceptor in the ETC?
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Ch. 5 - Microbial Metabolism
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
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Table of contents
- Ch. 1 - The Microbial World and You18
- Ch. 2 - Chemical Principles20
- Ch. 3 - Observing Microorganisms Through a Microscope18
- Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells21
- Ch. 5 - Microbial Metabolism20
- Ch. 6 - Microbial Growth20
- Ch. 7 - The Control of Microbial Growth20
- Ch. 8 - Microbial Genetics19
- Ch. 9 - Biotechnology & DNA Technology20
- Ch. 10 - Classification of Microorganisms15
- Ch. 11 - The Prokaryotes: Domains Bacteria and Archaea14
- Ch. 12 - The Eukaryotes: Fungi, Algae, Protozoa, and Helminths17
- Ch. 13 - Viruses, Viroids, and Prions20
- Ch. 14 - Principles of Disease and Epidemiology21
- Ch. 15 - Microbial Mechanisms of Pathogenicity19
- Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host20
- Ch. 17 - Adaptive Immunity: Specific Defenses of the Host20
- Ch. 18 - Practical Applications of Immunology20
- Ch. 19 - Disorders Associated with the Immune System19
- Ch. 20 - Antimicrobial Drugs19
- Ch. 21 - Microbial Diseases of the Skin and Eyes21
- Ch. 22 - Microbial Diseases of the Nervous System19
- Ch. 23 - Microbial Diseases of the Cardiovascular and Lymphatic Systems20
- Ch. 24 - Microbial Diseases of the Respiratory System20
- Ch. 25 - Microbial Diseases of the Digestive System20
- Ch. 26 - Microbial Diseases of the Urinary and Reproductive Systems19
- Ch. 27 - Environmental Microbiology20
- Ch. 28 - Applied and Industrial Microbiology19
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 5, Problem 9
Why must NADH be reoxidized? How does this happen in an organism that uses respiration? Fermentation?
Verified step by step guidance1
Understand that NADH is the reduced form of NAD+, a crucial coenzyme that carries electrons during metabolic reactions. NAD+ must be available in its oxidized form to accept electrons and continue glycolysis and other metabolic pathways.
Recognize that if NADH is not reoxidized back to NAD+, the cell will run out of NAD+ and metabolic processes like glycolysis will halt, stopping ATP production and energy generation.
In organisms that use respiration, NADH is reoxidized by transferring its electrons to the electron transport chain (ETC). This process occurs in the mitochondria (or plasma membrane in prokaryotes), where electrons pass through a series of carriers and ultimately reduce oxygen to water, regenerating NAD+.
In organisms that rely on fermentation, NADH is reoxidized by transferring electrons to an organic molecule (such as pyruvate or a derivative), which acts as the final electron acceptor. This regenerates NAD+ without the use of an electron transport chain or oxygen.
Summarize that the key difference is that respiration uses an external electron acceptor (like oxygen) and an ETC to regenerate NAD+, while fermentation uses internal organic molecules to accept electrons and regenerate NAD+ to sustain glycolysis.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Role of NADH in Cellular Metabolism
NADH is a key electron carrier that stores energy by accepting electrons during metabolic reactions. It must be reoxidized to NAD+ to maintain the balance of redox reactions and allow glycolysis and other pathways to continue producing ATP.
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02:17
Introduction to Metabolism
Reoxidation of NADH in Respiration
In organisms that use respiration, NADH is reoxidized by transferring electrons to the electron transport chain, ultimately reducing oxygen to water. This process regenerates NAD+ and produces a large amount of ATP through oxidative phosphorylation.
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03:35Anaerobic Respiration
Reoxidation of NADH in Fermentation
In fermentation, NADH is reoxidized by transferring electrons to organic molecules, such as pyruvate or its derivatives, instead of oxygen. This regenerates NAD+ to sustain glycolysis but produces less ATP compared to respiration.
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Related Practice
Textbook Question
Write your own definition of the chemiosmotic mechanism of ATP generation. On Figure 5.16, mark the following using the appropriate letter:
a. The acidic side of the membrane
b. The side with a positive electrical charge
c. Potential energy
d. Kinetic energy
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Textbook Question
Use the following choices to answer the question.
a. E. coli growing in glucose broth at 35℃ with O2 for 5 days
b. E. coli growing in glucose broth at 35℃ without O2 for 5 days
c. Both a and b
d. Neither a nor b
Which culture produces the most ATP?
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Textbook Question
Fill in the following table with the carbon source and energy source of each type of organism.
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Textbook Question
Use the following choices to answer the question.
a. E. coli growing in glucose broth at 35℃ with O2 for 5 days
b. E. coli growing in glucose broth at 35℃ without O2 for 5 days
c. Both a and b
d. Neither a nor b
Which culture uses the most glucose?
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Textbook Question
Use the following choices to answer the question.
a. E. coli growing in glucose broth at 35℃ with O2 for 5 days
b. E. coli growing in glucose broth at 35℃ without O2 for 5 days
c. Both a and b
d. Neither a nor b
Which culture uses NAD+ ?
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