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

egestion

FASES OF DIGESTION:

• INGESTION
• CHEMICAL AND MECHANICAL DIGESTION
• ABSORPTION
• EGESTION

CHEMICAL DIGESTION:

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

Chemical digestion

Enzymes: Important chemicals

Work

Go to classroom and follow the link 'draw a model of the digestive system'.

• Draw the organs of the digestive system
• label the parts
• add the functions

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

Work

• Read pages 54-58
• Do questions digestive system#1 on classroom

Hand in your food diary OR lab report about food tests next lesson.