Digestion Of Biological Molecules

Question 1

Describe the digestion of starch.

Answer 1

In the mouth:
- salivary amylase hydrolyses the glycosidic bonds in starch to produce maltose.
In the stomach:
- there is no amylase so, there is no digestion.
In the duodenum:
- pancreatic amylase hydrolyses the glycosidic bond in starch to form maltose.
In the ileum:
- membrane-bound maltose hydrolyses the glycosidic bond in maltose to produce alpha glucose.

Question 2

Describe the Digestion of Proteins.

Answer 2

In the mouth:
- No protease is present so, no proteins are digested.
In the Stomach:
- Endopeptidase hydrolyses the internal peptide bond in polypeptide chains, forming smaller peptide chains.
In the duodenum:
- Exopeptidase hydrolyses the external peptide bonds in smaller polypeptide chains, forming dipeptides and amino acids.
In the ileum:
- Membrane-bound dipeptidase hydrolyses the peptide bonds in dipeptides, forming amino acids which can be absorbed into the blood stream.

Question 3

Describe the digestion of lipids.

Answer 3

In the mouth & stomach:
- No lipase is present so, no lipids can be digested.
In the duodenum:
- Bile is produced in the liver and stored in the gall bladder.
- Bile is released into the duodenum where it emulsifies fats to form smaller fat droplets.
- Pancreatic lipase hydrolyses ester bonds in lipids, forming fatty acids and glycerol.
- Bile salts, fatty acids and glycerol form micelles.
In the ileum:
- Membrane-bound lipase hydrolyses ester bonds in triglycerides, forming fatty acids and glycerols.

Question 4

What is digestion?

Answer 4

Digestion is the hydrolysis of large, insoluble molecules into smaller, soluble molecules so that they can be absorbed into the bloodstream.