Which of the following are true with regard to anaerobic respiration in bacteria? P. The final electron acceptor is an inorganic substance other than molecular oxygen Q. The number of ATP molecules produced per glucose molecule is more than that produced in aerobic respiration R. The number of ATP molecules produced per glucose molecule is less than that produced in aerobic respiration S. Only substrate level phosphorylation is used to generate ATP
Anaerobic Respiration in Bacteria: Key Characteristics
Let's examine the given statements about anaerobic respiration in bacteria:
Statement P: The final electron acceptor is an inorganic substance other than molecular oxygen. This statement is true. Anaerobic respiration fundamentally differs from aerobic respiration by utilizing alternatives to oxygen ($O_2$) as the final electron acceptor. These are typically inorganic molecules such as nitrate ($NO_3^-$), sulfate ($SO_4^{2-}$), ferric iron ($Fe^{3+}$), or fumarate.
Statement Q: The number of ATP molecules produced per glucose molecule is more than that produced in aerobic respiration. This statement is false. Aerobic respiration, using oxygen, harvests significantly more energy because oxygen is a highly electronegative final electron acceptor, allowing for a greater proton gradient to be established across the membrane.
Statement R: The number of ATP molecules produced per glucose molecule is less than that produced in aerobic respiration. This statement is true. Since the alternative electron acceptors used in anaerobic respiration are less electronegative than oxygen, the electron transport chain generates a smaller proton motive force. This results in less ATP synthesis via chemiosmosis compared to aerobic respiration.
Statement S: Only substrate level phosphorylation is used to generate ATP. This statement is false. While substrate level phosphorylation (e.g., during glycolysis) generates ATP in anaerobic respiration, many pathways also employ an electron transport chain coupled with chemiosmosis (oxidative phosphorylation) using an alternative final electron acceptor. This process contributes to ATP generation, although less efficiently than in aerobic conditions.
Conclusion: Based on the analysis, statements P and R are the correct descriptions of anaerobic respiration in bacteria.
The correct option is C (P and R only).
Important Questions from Photosynthesis Respiration and Electron Transport Chain
- Correctly match the Inhibitor with its respective Function in mitochondrial respiration.
Inhibitor Function P. FCCP 1. Inhibits cytochrome c oxidase Q. Cyanide 2. Makes the membrane permeable to protons R. Oligomycin A 3. Blocks mitochondrial uptake of succinate S. Butyl malonate 4. Inhibits ATP synthase - ATP biosynthesis takes place utilizing the $H^+$ gradient in mitochondria and chloroplasts. Identify the correct sites of $H^+$ gradient formation.
Match the compounds in Group I with the correct entries in Group II.
Group I Group II P) Cyanide 1) K$^+$ ionophore Q) Antimycin A 2) Electron transfer from cytochrome b to cytochrome c$_1$ R) Valinomycin 3) F$_1$ subunit of ATP synthase S) Aurovertin 4) Cytochrome oxidase 5) Adenine nucleotide translocase - During photorespiration under low $CO_2$ and high $O_2$ levels, $O_2$ reacts with ribulose 1,5- bisphosphate to yield
Match items in Group I with Group II.
Group I Group II
P. Glycolytic pathway 1. Chloroplast
Q. Eukaryotic oxidative metabolism 2. Glyoxysomes
R. Glyoxylate cycle 3. Mitochondria
S. Calvin cycle 4. Cytosol
