Chapter 7, Problem 1BYB

Summary Introduction

To write:

The differences between the aerobic and anaerobic pathways.

Given:

Aerobic pathways produce more ATPs compared to anaerobic pathways.

Introduction:

There are two types of respiration aerobic and anaerobic. Aerobic pathways utilize oxygen while anerobic pathways do not use oxygen. Glycolysis is the first step of respiration common to both aerobic and anaerobic. The end product of glycolysis, which is pyruvate has different fates in aerobic and anaerobic pathways.

Explanation of Solution

In aerobic pathways, the 2 molecules of pyruvate produced from one molecule of glucose during glycolysis are converted to 2 molecules of acetyl CoA. Each molecule of acetyl CoA enters the tricarboxylic acid (TCA) cycle or the Krebs cycle which occurs in the mitochondria. In the Krebs cycle, the acetyl CoA undergoes sequential modifications producing NADH and FADH₂. These products then enter the electron transport chain which produces ATP, with utilization of the oxygen. Approximately, 36 molecules of ATP are produced from a single glucose molecule in the aerobic pathways.
In anaerobic pathways, the 2 molecules of pyruvate undergo fermentation process. Many cells like tumour cells and muscle cells convert pyruvate to lactate. Anaerobic organisms like yeast, convert pyruvate to acetaldehyde and acetaldehyde to ethyl alcohol. During both the processes, 2 molecules of ATP are produced. This process takes place in the cytoplasm.

One of the major differences in the aerobic and anaerobic pathways is the ATP production. Aerobic pathway is able to extract approximately 36 molecules of ATP and anaerobic pathway is able to extract only 2 molecules from each glucose molecule.

Conclusion

The aerobic pathways occur in mitochondria while anaerobic takes place in the cytoplasm. The aerobic pathway utilizes oxygen and anaerobic pathways do not use oxygen. The aerobic pathway has high energy yield compared to anaerobic pathway. Therefore, comparatively the aerobic pathways are more efficient than the anaerobic pathways.