Biology Notes
Chapter 4: Food and Digestion
SQs:
1. Why do we need food?
We need food for three main reasons:  To supply us with a ‘fuel’ for growth.
 To provide materials for growth and repair of tissues
 To help fight disease and keep our bodies healthy.
2. What is diet?
The food we eat is called our “diet”.
3. What is a balanced diet?
A diet that contains all necessary food types and in the correct amounts and proportions to
keep body healthy.
4. What are the substances need for the body to work properly and stay healthy?
Carbohydrates, lipids, proteins and vitamins along with dietary fibre and water. Food
should provide you with all of these substances but they must also be present in right
amounts.
5. What is the use of carbohydrate?
Carbohydrates make up only 1% of the mass of human body. They are body’s main ‘fuel’
for supplying cells with energy by oxidizing glucose in process of cell respiration. Glucose
and other sugars belong to one group of carbohydrates
6. Where is glucose found?
Naturally in many sweetest tasting foods such as fruits and vegetables.
7. What is fructose and lactose?
Fructose is monosaccharide sugar found in fruits and lactose is sugar found in milk ( also
disaccharide of glucose and galactose)
8.What is sucrose?
Disaccharide made from glucose and fructose. Main sugar transported in phloem of plants.
9.What are the physical properties of sugar?
 Taste sweet
 Soluble in water
10. Where do we get the sugar we need?
Natural foods such as fruits and vegetables and from digestion of starch.
11.What is starch?
Polysacchride of glucose that is large, insoluble molecule and acts as storage carbohydrate
in plants.
#Sugar content
Can of cola= 7 tablespoons (27g) of sugar
Tin of baked beans=10g
What is glycogen?
Polysachride of glucose that acts as storage carbohydrate in animals and fungi. Found in
liver and muscles.
#Breakdown of starch and glycogen to be absorbed into blood.
What is cellulose?
Polysaccharide of glucose that forms plant cells walls. Cannot be digested by humans as gut
doesn’t make enzyme need to breakdown cellulose molecule. This means it cant be used as
source of energy. It forms dietary fibre which gives muscles of guts something to push
against as food is moved through intenstine. This helps to keep the gut contents moving,
avoiding constipation and helping to prevent serious disease of intestine (colitis and bowel
cancer).
#Sugar types
Monosaccharide – single sugars
Disaccharride- Two monosaccharides joined together
Polysaccharides- Polymers of sugar