Chapter 8, Problem 1FIB

Summary Introduction

Introduction:

The breakdown of glucose is carried out in two major processes: glycolysis and cellular respiration. Glucose breakdown starts in the cytosol of the cell through glycolysis and further proceeds to the cellular respiration in the presence of oxygen. Cellular respiration occurs in the mitochondrion of the cell.

Answer to Problem 1FIB

Correct answer:

The complete breakdown of glucose in the presence of oxygen occurs in two stages: glycolysis and cellular respiration. The first of these stages occur in the cytosol of the cell, and the second stage occurs in organelles called mitochondria. Which stage generates the most ATP? Cellular respiration.

Explanation of Solution

Glycolysis takes place in the cytosol of the cell and it involves both the energy investment and energy harvesting stage. During glycolysis six-carbon, glucose molecule breaks down into two molecules of pyruvate. In the energy investment stage, two ATP molecules are used to convert glucose into fructose bisphosphate, which further breaks down into two molecules of glyceraldehyde-3-phosphate. During energy harvesting stage, the G3P molecules undergo a series of reactions that capture energy in four ATP and two NADH molecules.

Cellular respiration is the second stage in the breakdown of glucose after glycolysis and it occurs in mitochondria of the cell. Cellular respiration occurs only in the presence of oxygen. Two molecules of pyruvate produced in glycolysis breakdown into six carbon dioxide molecules and six water molecules. During cellular respiration, the chemical energy from two pyruvate molecules is used to produce 34 ATP.

Conclusion

Glycolysis and cellular respiration both are the important phase in the breakdown of glucose. Glycolysis occurs in cytosol while cellular respiration occurs in mitochondria of the cell.