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.24 Sucrase, 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)

Animation of enzymes Which enzyme is where?

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

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

Digesting starch

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

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

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

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

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

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

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

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

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

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