Lesson 1
Digestion
Chapter 3
• Recognize the organs of the alimentary canal and know their
functions.
• Understand the importance of mechanical digestion in the mouth.
• Understand the function of enzymes as biological catalysts in breaking
down food to simple chemicals.
The breakdown of food
• Your food needs to be broken down so it can enter the cells in your
body.
• When food is broken down it releases nutrients
• What nutrients are we talking about?
The breakdown of food
• Your food needs to be broken down so it can enter the cells in your
body.
• When food is broken down it releases nutrients
• What nutrients are we talking about?
•
•
•
•
•
Carbohydrates
Fats
Proteins
Vitamins
Minerals
The breakdown of food
• Our food needs to be broken down into very
SMALL molecules so it can pass through the
wall of our intestine.
• Digestion = process of breaking down food
into substances that can be used by the
body
• There are two main ways food is broken
down
• Physical breakdown
• Chemical breakdown
• Can you guess what happens in each of
those processes?
Physical breakdown of food
• Food is physically broken down from large pieces into small pieces in
the mouth.
• What role do teeth play in the breaking down of food?
Physical breakdown of food
• There are four
kinds of teeth, do
you know their
function?
Physical breakdown of food
• There are four
kinds of teeth, do
you know their
function?
Physical breakdown of food
• There are four
kinds of teeth, do
you know their
function?
Physical breakdown of food
• There are four
kinds of teeth, do
you know their
function?
Physical breakdown of food
• There are four
kinds of teeth, do
you know their
function?
Teeth
• Baby (milk) teeth= 20 teeth
• Adults (permanent) teeth = 32 teeth
•
http://www.childrensuniversity.manchester.ac.uk/learning-activities/science/teethand-eating/uses-of-teeth/
Teeth
• Tooth anatomy:
• http://www.crickweb.co.uk/ks2science.html#teeth
Teeth
• Dental decay.




It is the breakdown of teeth due to bacteria activity.
Symptoms: appearance of a white/brown spot, formation of
a hole, pain, difficulty with eating.
Complications: tooth loss, abscess, infection..
https://www.youtube.com/watch?v=zGoBFU1q4g0
Teeth
• https://youtu.be/_oIlv59bTL4
Mechanical digestion
What can be done to avoid dental decay?
 Brush your teeth at least twice a day , but ideally after each meal.
 Clean between your teeth daily with a dental floss.
 Use a mouthwash daily, preferably containing fluoride and antiseptic
ingredients.
 Keep a balanced diet, but avoid simple sugars contained in sugary
snacks, soda pop…
 Go to the dentist regularly!
 http://www.childrensuniversity.manchester.ac.uk/interactives/scienc
e/teethandeating/lookingafter/
Chemical breakdown of food
• Carbohydrates, fats and
proteins are made from
large molecules which
consist of smaller molecules
joined together
Chemical breakdown of food
• Large molecules don’t dissolve in
water and can’t pass through
the lining of the digestive system
into the body.
• Smaller molecules (which they
are made from) do dissolve in
water and can pass through the
lining of the digestive system
into the body.
Enzymes
• Made from proteins
• CATALYST - Speed up chemical reactions without being changed or
used up in the reaction
• Digestive enzymes speed up the breakdown of the large molecules
into smaller ones
Activity
• Textbook
• Question 1 & 2 page 37
• Workbook
• Question 1 page 16
• Fast track
• Workbook – Question 2 & 3 page 16 & 17