Name and briefly describe the 4 stages of aerobic respiration of glucose.

Question

What will be an ideal response?

Answer 1

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Stage 1: Glycolysis. In this pathway, glucose (a 6-carbon compound) is oxidized and forms 2 molecules of the 3-carbon compound pyruvate, produces NADH + H+, and generates a net of 2 molecules of ATP. Glycolysis occurs in the cytosol of cells.

Stage 2: Transition reaction. The transition reaction converts 2 molecules of the 3-carbon pyruvate from glycolysis into 2 molecules of the 2-carbon molecule acetyl-CoA (Fig. 9-6). The transition reaction also produces NADH + H+ and releases carbon dioxide (CO2) as a waste product. The transition reaction is given this name because these molecules are transitioning from the cytosol into the mitochondria of cells where this reaction occurs.

Stage 3: Citric acid cycle. In this pathway, acetyl-CoA enters the citric acid cycle, resulting in the production of NADH + H+, FADH2, and ATP. Carbon dioxide is released as a waste product. Like the transition reaction, the citric acid cycle takes place within the mitochondria of cells.

Stage 4: Electron transport chain. The NADH + H+ produced by stages 1 through 3 of cellular respiration and FADH2 produced in stage 3 enter the electron transport chain, where NADH + H+ is oxidized to NAD+ and FADH2 is oxidized to FAD. At the end of the electron transport chain, oxygen is combined with hydrogen ions (H+) and electrons to form water. The electron transport chain takes place within the mitochondria of cells. Most ATP is produced in the electron transport chain; thus, the mitochondria are the cell's major energy-producing organelles.