Chemical Digestion: Breaking Down Molecules for Absorption

 

What is Chemical Digestion?

Chemical digestion is the process of breaking down large, insoluble molecules into small, soluble molecules using enzymes.

Why is Chemical Digestion Important?

• Large molecules like starch, proteins, and fats cannot pass through the walls of the digestive system.
• Chemical digestion breaks them down into smaller molecules (like glucose and amino acids) that can be absorbed into the blood and used by the body.

 

Key Players: Digestive Enzymes

Enzyme	Substrate	Product	Where It Works
Amylase	Starch	Maltose (a sugar)	Mouth (saliva), small intestine
Protease	Proteins	Amino acids	Stomach, small intestine
Lipase	Fats (lipids)	Glycerol and fatty acids	Small intestine

 

How Chemical Digestion Works

1. Carbohydrate Digestion

• Starts in the Mouth:
  • Salivary glands produce amylase, which breaks down starch into maltose.
• Continues in the Small Intestine:
  • Pancreatic amylase breaks down remaining starch.
  • Maltase converts maltose into glucose.

 

 

 

Stages of Food Breakdown

Food goes through 5 stages as it travels through the digestive system:

• Ingestion: Taking in food and drink through the mouth.
• Mechanical Digestion: Breaking food into smaller pieces without changing the molecules.
• Chemical Digestion: Breaking large, insoluble molecules into small, soluble ones.
• Absorption: Moving small food molecules and ions into the blood through the intestinal wall.
• Assimilation: Using digested food molecules in body cells, where they become part of the cells.
• Egestion: Removing undigested or unabsorbed food as faeces through the anus.

 

•  The role of chemical digestion is to produce small soluble molecules that can be absorbed