3.2 Mechanical and chemical digestion

Digestion

The process by which the body breaks down food into smaller molecules, so that nutrients can be absorbed into the bloodstream and used by the cells.

The sites of digestion

• Mouth

• Stomach

• Small intestine

Another name for carbohydrates

Starch

Another name for fats

Lipids

The two main types of digestion

Mechanical and Chemical

Mechanical digestion

The physical breakdown of food into smaller pieces.

Where mechanical digestion begins

In the mouth

Mechanical digestion in the mouth

• The teeth breaks down the food by chewing

• The tongue helps move the food and mixes it with saliva, forming bolus

Where mechanical digestion continues

In the stomach

Mechanical digestion in the stomach

Muscles contract and relax in a process called churning.

Churning

A process where stomach and intestinal muscles contract to break down food and mix it with digestive juices

Importance of mechanical digestion

It increases the surface area of the food.

Chemical digestion

The process by which enzymes break down large food molecules into smaller molecules.

Where chemical digestion begins

In the mouth

Chemical digestion in the mouth

The saliva contains amylase, which breaks down carbohydrates.

Chemical digestion in the stomach

The stomach contains pepsin enzymes, which break down proteins

Chemical digestion in the small intestine

• There are enzymes in the small intestine that continue digestion

• Trypsin breaks down proteins into smaller peptides.

• Pancreatic amylase breaks down starches (carbohydrates) into maltose.

• Lipase breaks down lipids (fats) into fatty acids and glycerol.

The importance of mechanical digestion

It breaks down food into smaller pieces and increases the surface area, making it easier for enzymes to work.

The importance of chemical digestion

It breaks large food molecules into small soluble molecules that can be absorbed into the bloodstream and used by the body’s cells.

Enzymes

Biological catalysts that break down large food molecules into smaller, absorbable units.

Amylase

A digestive enzyme produced by the salivary glands and the pancreas.

Function of the amylase

It acts in the mouth and small intestine to break down starch (complex carbohydrates) into maltose (simpler sugars).

Pepsin

A digestive enzyme produced by the stomach.

Function of the pepsin

It acts in the stomach to break down proteins into peptides.

Trypsin

A digestive enzyme produced by the pancreas.

Function of the trypsin

It acts in the small intestine to break down proteins into peptides.

Lipase

A digestive enzyme produced by the pancreas.

Function of the lipase.

It acts in the small intestine to break down lipids into fatty acids and glycerol.