In which stage of cellular respiration, is the initial input (glucose), considered to have been completely oxidised? Question 18Select one: a. Pyruvate oxidation b. Citric acid cycle c. Electron transport chain d. Glycolysis

The stage of cellular respiration where the initial input (glucose) is considered to have been completely oxidized is the Citric acid cycle (b).

Here's a step-by-step explanation:

1. Glycolysis: This is the first stage of cellular respiration. One molecule of glucose (6 carbons) is broken down into two molecules of pyruvate (3 carbons each). However, glucose is not completely oxidized in this stage.

2. Pyruvate Oxidation: In this stage, each pyruvate molecule is converted into Acetyl CoA (2 carbons) and one molecule of carbon dioxide is released. Still, the glucose molecule is not completely oxidized.

3. Citric Acid Cycle (also known as Krebs Cycle or TCA Cycle): This is the stage where glucose is completely oxidized. Each Acetyl CoA enters the cycle and is completely oxidized to carbon dioxide.

4. Electron Transport Chain: This is the final stage of cellular respiration where the energy from electrons is used to create a proton gradient and ultimately produce ATP. However, the complete oxidation of glucose has already occurred in the Citric Acid Cycle.