CONCEPTS IN BIOLOGY

PART II. CORNERSTONES: CHEMISTRY, CELLS, AND METABOLISM

 

6. Biochemical Pathways—Cellular Respiration

 

6.4. Aerobic Cellular Respiration in Prokaryotes

The discussion so far in this chapter has dealt with the process of aerobic cellular respiration in eukaryotic organisms. However, some prokaryotic cells also use aerobic cellular respiration. Because prokaryotes do not have mitochondria, there are some differences between what they do and what eukaryotes do. The primary difference involves the electrons carried from glycolysis to the electron-transport system. In eukaryotes, the electrons released during glycolysis are carried by NADH and transferred to FAD to form FADH2 in order to get the electrons across the outer membrane of the mitochondrion. Because FADH2 results in the production of fewer ATPs than NADH, there is a cost to the eukaryotic cell of getting the electrons into the mitochondrion. This transfer is not necessary in prokaryotes, so they are able to produce a theoretical 38 ATPs for each glucose metabolized, rather than the 36 ATPs produced by eukaryotes (table 6.2).

TABLE 6.2. Aerobic ATP Production: Prokaryotes vs. Eukaryotic Cells

Stage of Aerobic Cellular Respiration

Prokaryotes

Eukaryotes

Glycolysis

Net gain 2 ATP

Net gain 2 ATP

Krebs cycle

2 ATP

2 ATP

ETS

34 ATP

32 ATP

Total

38 ATP

36 ATP

 

6.4. CONCEPT REVIEW

8. How is aerobic cellular respiration different in prokaryotic and eukaryotic organisms?