List the chemical changes which a starch molecule undergoes from the time it reaches duodenum to the time it's carbon atoms become part of the carbon dioxide molecules.Where in the body do they occur?

1. Hydrolysis: In the duodenum, starch molecules are broken down into smaller glucose molecules through the process of hydrolysis. This occurs in the small intestine.

2. Absorption: The glucose molecules are then absorbed into the bloodstream through the walls of the small intestine.

3. Cellular respiration: Once in the bloodstream, the glucose molecules are transported to cells throughout the body where they undergo cellular respiration. During this process, the glucose molecules are broken down further to release energy, with carbon atoms eventually becoming part of carbon dioxide molecules. Cellular respiration occurs in all cells of the body, particularly in the mitochondria.

Chemical Changes of Starch in the Digestive Tract

Duodenum

- Salivary amylase: Breaks down starch into dextrins and maltose.
- Pancreatic amylase: Further degrades dextrins and maltose into glucose.

Small Intestine

- Small intestinal lactase: Breaks down lactose (a sugar found in milk) into glucose and galactose.
- Small intestinal sucrase: Breaks down sucrose (a sugar found in fruits and vegetables) into glucose and fructose.

Absorption into Bloodstream

- Glucose, galactose, and fructose are absorbed into the bloodstream through the small intestine.

Liver

- Gluconeogenesis: Convert fructose and galactose into glucose.

Cells

- Glycolysis: Breaks down glucose into pyruvate.
- Pyruvate oxidation: Converts pyruvate into acetyl-CoA.
- Citric acid cycle (Krebs cycle): Oxidizes acetyl-CoA to produce carbon dioxide.

Carbon Dioxide Exhalation

- Carbon dioxide diffuses into the blood and is exhaled through the lungs.