Enzymes and Digestion

Question 1

What is the structure and function of the major parts of the digestive system?

Answer 1

-Oesophagus carries food from the mouth to the stomach.
-Stomach has an inner layer that produces enzymes.
-Ileum is a long muscular tube with many villi. It produces enzymes that further digest and absorb food.
-Large intestine absorbs water.
-Rectum stores faeces before egestion.

Question 2

How does the digestive system break down food physicaly and chemically?

Answer 2

=PHYSICAL DIGESTION
-Teeth chewing
-Stomach muscles churning

=CHEMICAL DIGESTION
-Hydrolysis by digestive enzymes such as carbohydrase, lipase and protease

Question 3

Describe the nature of carbohydrate digestion.

Answer 3

-Salivary amylase hydrolyses starch to maltose
-Amylase is denatured by stomach acid
-Pancreatic amylase continues hydrolysis (Alkaline salts are also produced here)
-Maltase (MBD) hydrolyses maltose sugar

-Sucrase and Lactase also act to hydrolyse sucrose and lactose.

Question 4

Describe the nature of lipid digestion.

Answer 4

-Hydrolysed by lipase enzymes to form fatty acids and monoglycerides
-Initially split up into micelles by bile salts (Emulsification)
-Increases SA:V for lipase to work on

Question 5

Describe the nature of protein digestion.

Answer 5

-Referred tp as a ‘peptidase’:
=Endopeptidases hydrolyse peptide bonds between amino acids in the middle of a protein molecule
=Exopeptidases hydrolyse peptide bonds on the terminal amino acids of peptide molecules formed by endopeptidases
=Dipeptidases hydroyse peptide bonds between two amino acids of a dipeptide. Membrane-bound, being part of the cell-surface membrane of epithelial cells in the ileum.