A Digestion Question

[nigel123]

A glassful of whole milk contains lactose, proteins, butterfat (mostly triglycerides), vitamins and minerals. Explain what will happen to each component in your digestive tract.

[nigel123]

just curious..
in the mouth.. enzyme amylase is secreted to digest starch into maltose

The milk contains lactose a dissacharide. so is the lactose digested in the mouth by the amylase?

[mith]

you could write a whole essay on that. And someone apparently did

http://www.biology-online.org/9/16_dige ... n_food.htm

[MrMistery]

Vitamins and minerals are absorbed under their present state. They do not suffer any transformations.
Lipids are broken down by salivar lipase(Yes, there is such an enzyme), go through the stomach withough being attacked by any enzyme and are then attacked by intestinal and pancreatic enzymes.
Cazein(the protein in milk) is broken down in the stomach first, the the digested is finalized in the small intestine.
Lactose is NOT attacked by salivar amylase. It is attacked by the enzyme lactase in the small intestine

[mith]

that's odd, our tutorial says that amylase breaks down carbs...

[MrMistery]

What does carbs mean?

[canalon]

What does carbs mean?

Carbohydrates... usually it means sugars

[MrMistery]

Lol... Sorry i am not used to some of these words.
Now, about that lactose
As we know, enzymes have an incredible specificity, each enzyme only catalyses a single chemical reaction. Ptialine catalyses the reaction of decomposing starch into a lot of dissacharides. It is true that it breaks down carbs(as you modern people say ) but only some carbs: starch

[surya]

Casein is digested by a protease in gastic juice called rennin.Casein is broken down to paracasein.By the way rennin is not produced in adults.

Intestinal juice contains disaccharases.Lactose is broken down to glucose and galactose by lactase(disaccharase)

[MrMistery]

Rennin, or labferment, is present in the stomach of adults, only in a much smaller amount. And it doesn't exactly break down casein, it just turns the caseinogen into an insoluble form called Calcium paracazeinat(don't know if i translated it correctly)

[surya]

My Biology teacher had mentioned in class that rennin is not produced in adults.She also added that this was the reason why doctors ask patients to discontinue drinking milk after a certain age .but ,she had said that in an offhand tone.Rennin was not our major topic of discussion and i think she didnt bother to explain about that in detail.thanx a lot for correcting me.

[MrMistery]

I'm sorry, your teacher was wrong. It's that the enzyme is in such a small amount in the stomach of adults, it can not do much...