During which of the phases of cellular respiration is the majority of ATP formed?
Glycolysis
All phases produce the same number of ATP molecules.
Oxidative phosphorylation (Electron Transport Chain)
Krebs cycle
The Correct Answer is C
A. Glycolysis: Glycolysis produces a small amount of ATP directly through substrate-level phosphorylation, yielding 2 ATP molecules per glucose molecule. While it initiates the breakdown of glucose to pyruvate, the majority of energy is not generated at this stage.
B. All phases produce the same number of ATP molecules: ATP production is not uniform across the phases of cellular respiration. Each phase contributes differently, with oxidative phosphorylation generating the largest share of ATP, making this statement incorrect.
C. Oxidative phosphorylation (Electron Transport Chain): The electron transport chain and chemiosmosis in oxidative phosphorylation produce the majority of ATP during cellular respiration, typically yielding 34 ATP per glucose molecule. High-energy electrons from NADH and FADH₂ drive proton pumping across the mitochondrial membrane, creating a proton gradient that powers ATP synthase to generate large quantities of ATP.
D. Krebs cycle: The Krebs cycle produces a small number of ATP molecules directly through substrate-level phosphorylation (1 ATP per cycle per acetyl-CoA). Its main contribution is generating NADH and FADH₂, which carry electrons to the electron transport chain for the production of most ATP.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
In gram-negative bacteria, the cell envelope is a complex structure composed of three main layers: an inner (cytoplasmic) membrane, a periplasmic space, and an outer membrane. The inner membrane is a phospholipid bilayer that regulates transport and energy production. The periplasmic space lies between the inner and outer membranes and contains a thin layer of peptidoglycan along with enzymes involved in nutrient processing and defense. The outer membrane contains lipopolysaccharides (LPS), porins, and other proteins that provide structural support, act as a barrier to certain antibiotics, and contribute to the organism’s pathogenicity.
100 Multiple Choice 0.5 points
Correct Answer is D
Explanation
A. Transduction: Transduction is the transfer of bacterial DNA from one cell to another via a bacteriophage (virus). It does not require direct physical contact between bacterial cells; the virus mediates the DNA transfer.
B. Transformation: Transformation involves the uptake of free DNA fragments from the environment by a bacterial cell. Physical contact between cells is not necessary, as the DNA is incorporated from the surrounding medium.
C. Transduction and conjugation: While conjugation requires physical contact, transduction does not. Therefore, combining the two does not accurately describe a process that exclusively requires cell-to-cell contact.
D. Conjugation: Conjugation is a process in which one bacterial cell transfers DNA directly to another through a pilus (sex pilus). Physical contact is essential for this mechanism, making it the only option listed that requires cell-to-cell interaction for DNA transfer.
E. Transformation and conjugation: Transformation does not require physical contact, so pairing it with conjugation does not correctly reflect the requirement for contact in all listed processes. Only conjugation depends on direct contact.
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