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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
3.1.2 Starch digestion and lactose intolerance
p.24Sucrase, lactase, salivary amylase,
pancreatic amylase, maltase, intestinal epithelium, lactose intolerance
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)
• Begins in the mouth
• Continues in the small intestine (pancreatic amylase)
• Is completed in the small intestine (intracellular maltase)
Which enzyme is where?
Animation of enzymes
Starch digestion
1. Draw briefly fig 12. Add labels3. Add ‘Maltase produced on the
LINING of small intestine’4. Add stomach denatures salivary
amylase5. Colour the gut with green for
neutral and red where it is acid
Finger-like projections of the lining of the
intestine vastly increase the surface area of
the epithelium
These projections arethe villi, and their
epithelial linings arehighly folded toform microvilli
The microvilli of the epithelial cells are
called brush borders, and many digestive
enzymes are embedded within their membranes
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)
MALTASEMALTOSE
MOLECULES
Lumen
Large Surface Area
Digestion of maltose
Alpha glucose either absorbed straight away or further down the small intestine
The activity of maltase is an example of intracellular digestion
The enzyme maltase catalyses the
hydrolysis of the disaccharide maltose
into molecules of alpha glucose
(monosaccharides) thereby completing
the digestion of starch
Digestion of disaccharidestext p.24-5 read then copy and complete
disaccharide Molecular formula
Name enzyme
Where enzyme made
Product of hydrolysis
Molecular formula of product
maltose Epithelial lining (small intestine)
sucrose
lactose
Digestion of disaccharidestext p.24-5 read then copy and complete
disaccharide
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 C12H22O11 sucrase Epithelial lining (small intestine)
Glucose + fructose
2C6H12O6
lactose C12H22O11 lactase Epithelial lining (small intestine)
Glucose + galactose
2C6H12O6
All brush border enzymes
Lactose intolerance1. Which food is lactose
found in?2. Why do adults produce
less lactase than children?
3. What is lactose intolerance?
4. What are the symptoms?
5. What is the dietary problem for lactose intolerant people?
6. How can it be overcome?
7. Look at Q3 and 4 p.25
3.1.2 Starch digestion and lactose intolerance
Key word bingo – pick any 4Sucrase, lactase, salivary amylase,
pancreatic amylase, maltase, intestinal epithelium, lactose intolerance