This document defines food and the essential roles it plays in the human body. It explains that food provides nutrients to maintain life and growth, and to replenish energy stores. Food is broken down into smaller molecules called end products that the body can absorb and use for respiration, growth, and repairing cells. The five main classes of food are carbohydrates, proteins, fats, minerals, vitamins, and water. Each class breaks down into specific end products, such as glucose from carbohydrates and amino acids from proteins, that the body uses for energy, growth, and repair. The document also outlines the digestive process and how different enzymes break down the major food classes into absorbable molecules.

1. Made LF: Oyegoke D.O

2. What is FOOD?
***Any nutritious substance that people or animals
eat or drink or that plants absorb in order to
maintain life and growth. is called “FOOD”.

3. Energy is used up as we go about our daily activities.
With time the energy stored becomes almost empty
and thus needs replacement.
Food is used by the body for:
 RESPIRATION
 GROWTH
 REPAIR OF DEAD CELLS

4. CLASSES OF FOOD
There are five (5) classes of food:
 CARBOHYDRATES
 PROTEINS
 FAT AND OIL
 MINERAL SALTS
 VITAMINS
 WATER
WaterProtein
Mineral saltCarbohydrate
VitaminsFat & Oil

5. •Before food can be used by the body, it has to be
broken down into smaller molecules for easy
absorption.
•These small molecules are called the “end products”.
END PRODUCTS

6. FOOD CLASSES AND THEIR END PRODUCTS
FOOD CLASSES
 Carbohydrates
 Proteins
 Fat and Oil
END PRODUCTS
 Glucose
 Amino Acids
 Fatty Acids/ Glycerol

7. Why do we need food?
We need to consume a balanced diet which contains a variety of
food in the proportions shown in the diagram below.
The body needs:
• Carbohydrates which provide
energy.
• Proteins for repair and growth.
• Vitamins and minerals to keep
the body healthy.

8. Food Groups

9. What is a balanced diet?

10. What do carbohydrates provide?
***Starchy foods contain carbohydrates, which are made
of long chains of identical small sugar molecules.
Carbohydrate
1 Sugar molecule

11.  The body has to break these large food
molecules up into smaller pieces.
 The small sugar molecules are very useful.
The body can use them to make…
 This energy is used to make the body work.
ENERGY
What do carbohydrates provide?

12. What do proteins provide?
As with carbohydrates, proteins are made of chains of
chemicals. However, instead of the chain containing identical
molecules, in protein these molecules are different.
Protein is made up of chains of amino acids(End Products).
There are over 20 different kinds of amino acid.
Protein is used to allow the body to grow and to repair the
body.

13. What happens to food in the
“Digestive System”?

14. Food enters the stomach, which is basically a muscular bag, filled with
Hydrochloric acid (HCl).
Two things happen here:
• Chemical breakdown of the food.
• Microbes are destroyed.
food enters
from the gullet
cross section of stomach
digested food leaves
muscle tissue
The stomach

15. The large intestine
The remains of the food are then passed on to large intestine
(colon).
All that is left is waste material and water. The body will want to leave
the waste material within the digestive system but the water is
valuable and so it is re-absorbed here.
The waste material is passed to the rectum where it is stored until it
leaves the body through the anus.

16. Carbohydrates are chains of identical sugar molecules. The
enzyme called Carbohydrase breaks the chemical bonds
between the individual sugar molecules (called glucose) as part of
digestion.
Starch/ Carbohydrates
Carbohydrase
Long carbohydrate
Small
sugar

17. Fats
Fats are digested in two stages:
• Firstly, bile (released by the gall bladder) allows the fat to “mix” with water by
breaking the fat up into smaller droplets. This is called emulsification.
• Secondly, an enzyme called Lipase breaks the fats down into the smaller fatty acid
molecules and glycerol.
Bile
Lipase
+
Fat
Fatty
acid
Glycerol

18. After you have read and understood
this topic, please attempt the quiz
questions that follow in your blog. I
hope you will find it tasking and
interesting.