Choose all that apply to the part(s) of cellular respiration which occurs along the inner mitochondrial membrane Glycolysis Transition phase (also known as the preparatory phase) Krebs cycle (also known as the citric acid cycle) Electron transport chain Proton transport chain QUESTION 22 Choose all that apply to the part(s) of cellular respiration which produces ATP by substrate level phosphorylation Glycolysis Transition phase (also known as the preparatory phase) Krebs cycle (also known as the citric acid cycle) Electron transport chain Proton transport chain
Certainly! Here’s the correct answer followed by a detailed, textbook-style explanation.
QUESTION 1: Choose all that apply to the part(s) of cellular respiration which occurs along the inner mitochondrial membrane
✅ Electron transport chain
✅ Proton transport chain
Correct Answers:
- Electron transport chain
- Proton transport chain
QUESTION 2: Choose all that apply to the part(s) of cellular respiration which produces ATP by substrate level phosphorylation
✅ Glycolysis
✅ Krebs cycle (also known as the citric acid cycle)
Correct Answers:
- Glycolysis
- Krebs cycle
Explanation
Cellular respiration is a multi-step metabolic process that breaks down glucose to produce ATP, the cell’s main energy currency. It consists of four major stages: glycolysis, the transition phase, the Krebs cycle, and the electron transport chain (ETC). Each stage occurs in specific locations within the cell and utilizes distinct mechanisms for ATP production.
The electron transport chain and the associated proton transport chain occur along the inner mitochondrial membrane. These chains are responsible for oxidative phosphorylation, the most ATP-productive step in respiration. Electrons from NADH and FADH₂ are passed through protein complexes in the inner membrane. This electron movement powers the active transport of protons (H⁺) from the mitochondrial matrix to the intermembrane space, creating a proton gradient. The protons flow back into the matrix through ATP synthase, driving the synthesis of ATP. This entire mechanism is collectively referred to as chemiosmosis and occurs exclusively on the inner mitochondrial membrane.
In contrast, substrate level phosphorylation is a direct method of ATP synthesis, where a phosphate group is transferred from a phosphorylated intermediate to ADP. This occurs in the cytoplasm during glycolysis and in the mitochondrial matrix during the Krebs cycle. In glycolysis, two ATP molecules are produced this way. Similarly, the Krebs cycle generates one ATP (or GTP, depending on the cell type) per cycle via substrate-level phosphorylation. The transition phase does not produce ATP; instead, it generates NADH and acetyl-CoA. The ETC and proton transport chain produce ATP by oxidative phosphorylation, not by substrate-level phosphorylation.
Understanding where each stage occurs and how ATP is produced is key to grasping how cells efficiently harvest energy from glucose
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