Topic 3: Digestion + Absorption

Question 1

How is the small intestine adapted for the movement of substances?

Answer 1

-Internal walls folded into villi’s: Gives a large S.A
-Villi’s have walls that are one cell thick: Shortens diffusion pathway
-Villi’s have lots of capillaries: Helps maintain the concentration gradient by transporting absorbed nutrients away
-Many mitochondria: Provides ATP for active transport

Question 2

How are the epithelial cells adapted for efficient digestion?

Answer 2

-Many microvilli’s: Increases S.A for diffusion further
-Many mitochondria: Provides ATP for active transport
-Contains carrier proteins: Aid active transport
-Contains channel proteins: Aids facilitated diffusion

Question 3

Describe how Carbohydrates are digested.

Answer 3

In the mouth, salivary glands secretes amylase and the pancreas also secretes pancreatic amylase which is released into the small intestine which hydrolyses the glycosidic bonds in starch to form maltose. In the small intestine, it produces membrane bound disaccharidases (Maltase, Sucrase, Lactase). Maltase breaks glycosidic bonds to hydrolyse maltose into alpha-glucose. (Disaccharides to monosaccharides)

Question 4

How is sucrose made?

Answer 4

The condensation of a Glucose molecule and a fructose molecule

Question 5

How is lactose made?

Answer 5

The condensation of a galactose molecule and a glucose molecule

Question 6

How is maltose made?

Answer 6

The condensation of 2 alpha-glucose molecules