Topic: B2b Lesson: 2 Title: Enzymes and digestion

1
Topic B2bLesson 2Title Enzymes and digestion

• Aims Explain how enzymes are involved in
  digestion
• Starter Write down everything you can remember
  from key stage 3 about digestion, eg. what it is
  where it takes place...

2

• What is digestion?
• Breaking down large, insoluble molecules into
  smaller, soluble molecules that can be absorbed
  through the wall of the small intestine
• What breaks down the large molecules?
• Digestive enzymes made by specialised cells
  inside glands

3
The enzymes involved...

• Carbohydrates Simple sugars
• Proteins Amino acids
• Lipids (fats) Fatty acids glycerol

4

• Digestion animation (First 5 mins 15 secs)
• Listen carefully and make notes in your book.
  You will be quizzed after the animation so listen!

5
Mini test on digestive enzymes...

• Where are the following digested
• Carbohydrates mouth and small intestine
• Proteins stomach and small intestine
• Fats small intestine
• 2. What are the following broken down into by
  digestive enzymes?
• Carbohydrates ? simple sugars
• Proteins ? amino acids
• Fats ? fatty acids glycerol
• 3. Where are most enzymes produced? Pancreas

6
Why do you think there is acid in the stomach?

• Kills bacteria in food protects us
• Denatures proteins makes digestion easier
• Activates stomach enzymes these only work in
  acidic conditions
• Ever wondered why PEPSIN (stomach enzyme) doesnt
  digest our own stomach?
• Pepsin is inactive when first made and is only
  activated by HCL to start digesting proteins.

7
What does bile do?

• Bile is produced in the liver and stored in the
  gall bladder.
• The enzymes in the small intestine need an
  alkaline pH to work best, so bile passes into the
  small intestine and neutralises acid from the
  stomach.
• Bile also emulsifies fat droplets to increase
  their surface area

8
How are villi in the small intestine adapted to
absorb food?
9
(No Transcript)
10

• How are villi specialised to carry out their job
  of absorbing digested foods?

11
Answers

• Millions provide large surface area
• Each villus has many microvilli to further
  increase surface area
• Rich blood supply for absorbed nutrients to pass
  into and be taken around body
• Branch of lymphatic system takes absorbed fatty
  acids and glycerol away to be used or stored
• Villi wall one cell thick for rapid passing
  through of nutrients

12
Digestive system summary

• Salivary glands produce ________
• Liver produces ______
• Stomach produces ________ ________
• Gall bladder stores ________
• Pancreas and small intestine both produce
  ________, ________, and ________

13
Why do people have their stomachs stapled?

• stomach band

14
This powerpoint was kindly donated to
www.worldofteaching.com http//www.worldofteac
hing.com is home to over a thousand powerpoints
submitted by teachers. This is a completely free
site and requires no registration. Please visit
and I hope it will help in your teaching.