Monday 18/01/2021
B3.6: HOW THE DIGESTIVE SYSTEM WORKS
STARTER ACTIVITY: Retrieving prior knowledge
Based on what we have learnt so far, label each organs of the
digestive system in order. Write in your worksheet.
Salivary glands- mouth
A ____________________________
Oesophagus
B ____________________________
Liver
C ____________________________
Stomach
D ____________________________
Pancreas
E ____________________________
Small intestine
F ____________________________
Large intestine
G ____________________________
CHALLENGE
Do you remember what is the
difference between
‘egestion’ and ‘excretion’?
SELF-ASSESS CHALLENGE QUESTION
Egestion is the removal of undigested food from the body through
the anus as faeces.
Excretion is the removal of waste products, derived from cells’
metabolism, from the body. Examples are: (1) removal of carbon
dioxide from the lungs; (2) removal of urea from the kidneys, and
(3) removal of various toxins from the skin.
RECALLING IMPORTANT KEY POINTS
• The digestive system is the organ system that breaks food
down into small molecules; absorbs small molecules in the
bloodstream (villi) and egests undigested food (through anus).
• Digestion is helped by enzymes, which are biological catalysts
that speed up the rate of reactions by lowering the activation
energy of that reaction. All enzymes are PROTEINS and they
are NOT used up in the reactions they catalyse.
Monday 18/01/2021
B3.6: HOW THE DIGESTIVE SYSTEM WORKS
Learning objective
Be able to demonstrate and apply your knowledge & understanding
of enzymes involved in digestion (breaking down) of various food
molecules.
Lesson learning outcomes
Recall the main organs of the human digestive system and the
processes that take place in them.
Compare the enzymes that break down carbohydrates, proteins
and fats.
Discuss how various factors affect these enzymes differently.
Key words previously learnt
Enzyme, activation energy,
active-site, absorption,
villi and microvilli, egestion
New key words
Carbohydrase, amylase,
Protease, Pepsin, Tripsin
Lipase
LO1: Recall the main organs of the human digestive system
and the processes that take place in them.
INDEPENDENT ACTIVITY: For each name of process, match the
correct definition of what happens and put in the correct sequence.
Write the full sentence in your book .
In the digestive system the following processes take place:
1)_____________________________________________________
2)_____________________________________________________
3)_____________________________________________________
4)_____________________________________________________
Absorption
• removal of undigested food from the body
through the anus as faeces.
Ingestion
• large and insoluble molecules are broken down by
enzymes into small and soluble molecules.
Egestion
• food is introduced in the body by swallowing.
Digestion
• in the small intestine small and soluble molecules
pass into the blood stream through the villi.
LO1: Recall the main organs of the human digestive system
and the processes that take place in them.
SELF-ASSESSMENT: Check that you have done these correctly
In the digestive system the following processes take place:
1) Ingestion: food is introduced in the body by swallowing.
2) Digestion: large and insoluble molecules are broken down
by enzymes into small and soluble molecules.
3) Absorption: in the small intestine small and soluble
molecules pass into the blood stream through the villi.
4) Egestion: removal of undigested food from the body
through the anus as faeces.
LO2: Compare the enzymes that break down carbohydrates,
proteins and fats.
INDEPENDENT TASK: Extract the information from the videoclip to answer the questions in your worksheet.
Amylase
Protease
Lipase
Acids and alkalis
Where is it made?
Where is it made?
Where is it made?
Name the acid in the stomach
Where does it work?
Where does it work?
Where does it work?
Why do we have acid in the
stomach?
What does it do?
What does it do?
What does it do?
https://www.bbc.co.uk/bitesize/guides/z9pv34j/revision/3
LO2: Compare the enzymes that break down carbohydrates,
proteins and fats.
INDEPENDENT TASK: Extract the information from the videoclip to answer the questions in your worksheet.
Amylase
Protease
Lipase
Acids and alkalis
Where is it made? Where is it made?
• Salivary glands • Stomach
• Pancreas
(Pepsin)
• Small intestine • Pancreas
(Tripsin)
• Small intestine
Where does it
Where does it
work?
work?
• Mouth
• Stomach
• Small intestine • Small intestine
Where is it made? Name the acid in
• Pancreas
the stomach
• Small intestine Hydrochloric acid
What does it do?
Breaks down
carbohydrates
into maltose
What does it do?
Breaks down fats
into fatty acids
and glycerol
What does it do?
Breaks down
proteins into
amino acids
Where does it
work?
• Small intestine
Why do we have
acid in the stomach?
Hydrochloric acid
helps to break down
nutrients, such as
proteins. It also
protects from
harmful bacterial
and viral infections.
LO3: Discuss how various factors affect these enzymes
differently.
Enzymes that catalyse (speed up) reactions in different parts of
the digestive system have different optimal pH.
In order to work properly they have to have a specific value of pH.
What would happen if the pH was not optimal?
INDEPENDENT WORK
In your books answer the following summary questions
Figure 1
Plenary challenge
In your books, write a sentence that links as many key words
as possible from the list below (15 key words in total!)
amylase
protease lipase
stomach enzymes
acidic
pH
alkaline
curve catalyse carbohydrates
fats
amino acids optimum proteins
CHALLENGE QUESTION
Explain the importance of the digestion of food in terms of
the molecules involved and the role of enzymes in the gut.
[6 marks]