Question 3.2.6 [2 marks]Define the term cellular respiration

Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break down large molecules into smaller ones, releasing energy in the process.

This process can be summarized in three main stages:

1. Glycolysis: This is the first stage of cellular respiration. It occurs in the cytoplasm of the cell where one glucose molecule (a 6-carbon molecule) is broken down into two molecules of pyruvate (a 3-carbon molecule). This process produces a small amount of ATP and does not require oxygen.

2. Krebs Cycle (Citric Acid Cycle): This is the second stage of cellular respiration. It occurs in the mitochondria of the cell. Here, the pyruvate molecules are further broken down and electrons are transferred to carrier molecules. This process produces a small amount of ATP and requires oxygen.

3. Electron Transport Chain: This is the final stage of cellular respiration. It also occurs in the mitochondria. Here, the electrons from the carrier molecules are used to create a large amount of ATP. This is the stage that produces the most ATP and requires oxygen.

The overall equation for cellular respiration is:

C6H12O6 (glucose) + 6O2 (oxygen) -> 6CO2 (carbon dioxide) + 6H2O (water) + energy (as ATP)

The carbon dioxide and water are waste products that are excreted from the body. The ATP produced is used by the cell to carry out various functions.