digestive system-1

• Biologie
• Middelbare school
• havo, vwo
• Leerjaar 2

The digestive system

1

2

3

4

5

6

7

8

heart

large intestine

small intestine

stomach

lung

liver

brain

kidney

Digestion

Digestion: Breakdown of food molecules into small food molecules 

When food is digested it is absorbed  

Big vs. Small

Big molecules -> Insoluble can not get through the gut wall

Small molecules -> Soluble can get through the gut wall

Fases of digestion. Put them in the right order.

1

2

3

4

digestion

ingestion

absorption

elimination

FASES OF DIGESTION:

• INGESTION
• CHEMICAL AND MECHANICAL DIGESTION
• ABSORPTION
• ELIMINATION

CHEMICAL DIGESTION:

• BREAKING THE FOOD INTO EVEN SMALLER MOLECULES.
• USING ENZYMES TO BREAK DOWN THE FOOD MOLECULES. 

Chemical digestion

Enzymes: Important chemicals

Chemical digestion Step 1

• starts in: the mouth 
• the enzyme: amylase (a carbohydrase)
• the liquid: saliva 
• the nutrient: carbohydrates
• the products: glucose 

The enzymes in your saliva start breaking down the carbohydrate molecules into glucose.

Down the tube!

Oesophagus

Peristalsis: moving food down your oesaphagus (gullet)

Why is your stomach rumbling? 

-peristalsis, muscle activity

- mechanical digestion

-Empty stomach and intestines make a louder sound!

In your stomach

Digestive juices are added

• Proteases -> digestion proteins -> amino acids
• Hydrochloric acid -> acid PH, best for the enzymes + acidic environment also kills germs
• Rennin (only babies) makes milk solid, stays in the stomach longer

small           intestine

In your small intestine

2 important liquids added in the first part (the duodenum)

• Pancreatic juice (carbohydrases, proteases and lipases)
• Bile from the liver, stored in the gall bladder
• Bile is alkaline neutralises acid from the stomach
• Bile emulsifies fats, increases surface area of fats lipase enzymes to act upon

In your small intestine

Intestinal juice (carbohydrases, proteases, lipases) Complete digestion of food, made by the wall of the small intestine

Ingestion

Mechanical digestion

Chemical digestion

MOVING THE FOOD INTO YOUR MOUTH

BREAKING THE FOOD INTO SMALLER PIECES.

THIS IS DONE BY YOUR TEETH

BREAKING THE FOOD INTO EVEN SMALLER PIECES.

USING ENZYMES TO BREAK DOWN THE FOOD MOLECULES. 

Amylase is an example of a

1. Carbohydrase
2. Lipase
3. Protease

During the break down of proteins you get:

1. glucose
2. amino acids
3. fatty acids

The environment of the stomach is

1. Acidic
2. Alkaline

Which enzyme breaks down carbohydrates in the mouth?

1. Maltase
2. Amylase
3. Protease
4. Lipase

What enzyme aids in the breakdown of proteins in the stomach?

1. Lactase
2. Amylase
3. Pepsin
4. Sucrase

Which enzyme assists in the digestion of fats in the small intestine?

1. Amylase
2. Pepsin
3. Lipase
4. Maltase

Peter is 180cm and weighs 99 kilos.
Calculate his BMI and tell me if his BMI is healthy.