1. Homework
Produce an explanatory leaflet on the problem and solutions of lactose intolerance p25
Exemplars on next slide
text p.25 Q1-4 red
Small worksheet q
Questions from practical lesson

5. 3.1.2 Starch digestion and lactose intolerance
p.24
Sucrase, lactase, salivary amylase, pancreatic amylase, maltase, intestinal epithelium, lactose intolerance

6. Starch digestion begins in the mouth where three pairs of salivary glands secrete saliva into the buccal cavity
Saliva contains the enzyme amylase that catalyses the hydrolysis of starch into maltose and dextrins (short glucose chains)

7. Review – hydrolysis of maltose
Text p.22

8. Begins in the mouth
Continues in the small intestine (pancreatic amylase)
Is completed in the small intestine (intracellular maltase)

9. Animation of enzymes
Which enzyme is where?

10. Starch digestion Draw briefly fig 1 Add labels
Add ‘Maltase produced on the LINING of small intestine’
Add stomach denatures salivary amylase
Colour the gut with green for neutral and red where it is acid

11. Which enzyme, salivary or pancreatic amylase does most hydrolysis?
Why?

12. Digesting starch

13. epithelial linings are
Finger-like projections of the lining of the intestine vastly increase the surface area of
the epithelium
The microvilli of the epithelial cells are called brush borders, and many digestive enzymes are embedded within
their membranes
These projections are
the villi, and their
epithelial linings are
highly folded to
form microvilli

14. Microvilli forming the brush border Numerous mitochondria Nucleus
A number of digestive enzymes are located and function within the membranes that form the microvilli (brush border enzymes)
Nucleus

15. The activity of maltase is an example of intracellular digestion
Digestion of maltose
MALTASE
MALTOSE
MOLECULES
Alpha glucose either absorbed straight away or further down the small intestine
Lumen
Large Surface Area
The activity of maltase is an example of intracellular digestion

16. The enzyme maltase catalyses the hydrolysis of the disaccharide maltose into molecules of alpha glucose (monosaccharides) thereby completing the digestion of starch

17. Digestion of disaccharides text p.24-5 read then copy and complete
Molecular formula
Name enzyme
Where enzyme made
Product of hydrolysis
Molecular formula of product
maltose
Epithelial lining (small intestine)
sucrose
lactose

18. Digestion of disaccharides text p.24-5 read then copy and complete
Molecular formula
Name enzyme
Where enzyme made
Product of hydrolysis
Molecular formula of product
maltose
C12H22O11
maltase
Epithelial lining (small intestine)
2 glucose
2C6H12O6
sucrose
sucrase
Glucose + fructose
lactose
lactase
Glucose + galactose
All brush border enzymes

19. Lactose intolerance Which food is lactose found in?
Why do adults produce less lactase than children?
What is lactose intolerance?
What are the symptoms?
What is the dietary problem for lactose intolerant people?
How can it be overcome?
Look at Q3 and 4 p.25

21. 3.1.2 Starch digestion and lactose intolerance
Key word bingo – pick any 4
Sucrase, lactase, salivary amylase, pancreatic amylase, maltase, intestinal epithelium, lactose intolerance

22. Answers salivary amylase Sucrase Maltase intestinal epithelium Lactase
lactose intolerance
pancreatic amylase

23. membranes of the microvilli
The epithelial cells that line the villi of the small intestine synthesise molecules of the enzyme maltase, and insert them into the plasma
membranes of the microvilli
MALTASE
MALTOSE
MOLECULES
The glucose molecules formed from maltase activity are either released into the
lumen of the intestine and absorbed further along, or absorbed directly into the epithelial cells
Molecules of maltose bind to the maltase enzymes in the brush border and are hydrolysed into glucose molecules
The activity of the brush-border enzyme maltase is an example of intracellular digestion