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)

Review – hydrolysis of maltose

• Text p.22

• 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

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

2. Why?

Digesting starch

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

Answers

• salivary amylase• Sucrase• Maltase• intestinal epithelium• Lactase• lactose intolerance• pancreatic amylase