Chapter 7, Problem S3.2BYB

Summary Introduction

To explain:

The role of carbohydrates in living beings.

Introduction:

The main role of carbohydrates in the body is to produce energy. It is the main source of energy to the body. Carbohydrates are digested then metabolized inside the cells (cellular respiration) for energy (ATP) production.

Explanation of Solution

The source of carbohydrates to our body is food. The food one ingests is digested firstly. The digestion is completed in the small intestine and monosaccharides like glucose are obtained. These are then transported (absorbed via microvilli) through blood to all the cells in the body that require it.

The glucose molecules undergo glycolysis in the cytosol to give pyruvate. Depending whether the respiration was aerobic or anaerobic, the pyruvate enters citric acid cycle (mitochondrial matrix) or fermentation (in the cytosol), respectively.

In fermentation, either lactate or ethanol is produced. Before the citric acid cycle starts, pyruvate is oxidized into acetyl-CoA. This then enters the citric acid cycle to yield molecules with high energy electrons. The molecules are used in electron transport chain in the inner mitochondrial membrane to generate a proton motive force. This positive force is used to generate ATP molecules by oxidative phosphorylation.

Conclusion

The main role of carbohydrates in living beings is energy production by cellular respiration.