IB5.10.1 Objectives
B5 Lesson 10 Digestion
After studying this topic, you should be able to:
 explain why food has to be digested
 explain the role of enzymes in chemical digestion
 describe the functions of the parts of the human
digestive system
 explain how digested food molecules are absorbed
into the blood
© Oxford University Press 2011
Starter
Name and describe the function of each part
of the human digestive system.
mouth – food is chewed here
salivary glands – releases enzymes into the mouth
oesophagus – a.k.a. gullet
stomach – releases enzymes; churns food
pancreas – releases enzymes into small intestine
liver – makes bile
gall bladder – stores bile and releases it into small
intestine
small intestine – food is digested and absorbed here
large intestine – water and minerals are absorbed into
the blood, leaving faeces which pass out of the anus
(egestion)
The human digestive system
What is the difference between
physical digestion and chemical
digestion.?
Definition – Physical digestion.
• is the breaking of food into smaller pieces by:
– chewing in the mouth by teeth
– squeezing in the stomach
How does this help chemical digestion?
Definition – Chemical digestion
Carbohydrates, fats, and
proteins are digested by
enzymes. This is known as
chemical digestion.
•Can you name the enzyme responsible for digesting
each type of food?
Food
carbohydrates
fats (lipids)
proteins
•These are the enzymes.
•Where do they work?
Food
Type of enzyme
carbohydrates
carbohydrases
fats (lipids)
lipases
proteins
proteases
•This is where they work.
•What do they break food down into?
Food
Type of enzyme
Part of gut where
enzyme works
carbohydrates
carbohydrases
mouth and small
intestine
fats (lipids)
lipases
small intestine
proteins
proteases
stomach and
small intestine
•These are the products of digestion.
•Enzymes work well at specific pH values.
Look at the table.
Food
Type of enzyme
Part of gut where
enzyme works
Products of
digestion
carbohydrates
carbohydrases
mouth and small
intestine
Starch, converted
to maltose and
then to glucose, a
simple sugar
fats (lipids)
lipases
small intestine
fatty acids and
glycerol
proteins
proteases
stomach and
small intestine
amino acids
•What pH values do you think these
enzymes work best at and why?
 carbohydrases
 lipases
 proteases
Bile
• Liver makes it
• Gall bladder stores it
• Released into small intestine.
Emulsification
Small intestine
• Small digested food molecules are absorbed
into the blood plasma or lymph in the small
intestine by diffusion
Adaptations of the small intestine
• While watching the animation write down a
list of adaptation the small intestine has for
the efficient adsorption of digested food.
Large Intestine
• Adsorbs water and some minerals into blood.
• semi-solid waste that is left passes out of the
anus – egestion.