Chapter 8, Problem 28A

Summary Introduction

To define:

The given vocabulary termin a complete sentence.

Introduction:

Organisms obtain energy through a process called cellular respiration. This process occurs in two stages; glycolysis and aerobic respiration. Glycolysis is an anaerobic process. Aerobic respiration includes Krebs cycle and electron transport.

Answer to Problem 28A

Krebs cycle- A series of reactions in which pyruvate is broken down into carbon dioxide is called Krebs cycle.

Explanation of Solution

The end products of glycolysis are two ATP molecules and two pyruvate molecules. Most of the energy from the glucose is still present in pyruvate. In the presence of oxygen, pyruvate is transported into the mitochondrial matrix, where it is finally converted to carbon dioxide. The series of reactions involved in breaking down pyruvate to carbon dioxide is called Krebs cycle or tricarboxylic acid (TCA) cycle. It is also called citric acid cycle.

The Krebs cycle starts with acetyl CoA combining with a 4- carbon compound to form a 6- carbon compound known as citric acid. Citric acid is then broken down in a series of steps releasing carbon dioxide and generates one ATP, 3 NADH and 1 FADH₂. Finally acetyl CoA and citric acid are regenerated and the cycle continues. Two turns of Krebs cycle occurs for one glucose molecule.