Question

1. Track a piece of pizza through Mary’s digestive system by drawing a simplified sketch of how various biological molecules are processed by Mary’s digestive system. Start with the pizza entering through the mouth and show how the various enzymes break it down into nutrients that can be absorbed within the body. For this question, you may assume that the only biological molecules in the pizza are polysaccharides, from the starch-filled dough, and lactose, from the cheese. You may ignore any other molecules that might be present. You should also assume that Mary did NOT take her Lactaid medication when eating the pizza.
2. How would the digestion above change if Mary took Lactaid with her meal?

Answer 1

The digestion of polysaccharides starts from mouth where the salivary glands secrete salivary amylase. It contributes to partial digestion of polysaccharides and yields oligosaccharides. Pancreatic juice is secreted in duodenum which contains pancreatic amylase undergoes complete hydrolysis of polysaccharides into oligosaccharides. Oligosaccharides are converted to disaccharides by dextrinase enzyme. Disaccharides are converted to simple sugars by the enzyme disaccharidases. The simple sugars glucose, fructose and galactose are absorbed in the intestine and used for energy fuel.

Lactaid medication is a natural lactase enzyme supplement used for lactose intolerance. As Mary taking this medication usually, she may be subjected to lactose intolerance. Lactose intolerance is the condition in which the individual is unable to digest lactose due to absence of enzyme lactase, which is one of the disaccharidases.

If she takes the medication, the lactose present in the diet is digested by lactase enzyme supplement of lactaid. And it is converted to glucose and lactose which is absorbed in the intestine and utilized for energy process. So she remain unaffected by the lactose diet and she will be normal.

If Mary does not take her medication will lead to lactose intolerance condition. Lactose from the polysaccharides digestion and from cheese is unabsorbed in the intestine due to absence of lactase enzyme. This undigested lactose is digested by bacteria releasing gas and causes bloating. The remaining undigested lactose is eliminated from the system by diarrhoea. It eventually results in bloating, indigestion, cramps and diarrhoea.