Functions of enzyme in digestion

Question 1

What is gastric juice

Answer 1

It is a dilute solution of hydrochloric acid and two enzymes: pepsin and rennin

Question 2

What are the functions of dilute hydrochloric acid in the stomach

Answer 2

• Its stops the action of the salivary amylase
• It kills germs and potential parasites in ingested food
• Initiates the conversion of inactive form of pepsin (Pepsinogen) into pepsin
• Initiates the conversion of inactive form of rennin (Prorennin) into rennin
• Provides an acidic medium for the action of gastric enzymes

Question 3

What is the role of pepsin in the stomach

Answer 3

Pepsin catalyses the hydrolysis of proteins into short polypeptides or peptides

Question 4

What is the role of rennin in the stomach

Answer 4

Rennin commences the digestion of milk proteins by converting the soluble protein caseinogen into the insoluble casein, thus clotting or curdling milk proteins

Question 5

What does pepsin do to the insoluble casein

Answer 5

The insoluble casein remain in the stomach to be digested by pepesin

Question 6

What is pancreatic juice

Answer 6

Pancreatic juice contains sodium hydrogen carbonate and the enzymes pancreatic amylase, pancreatic lipase and trypsinogen

Question 7

What are brush border enzymes?

Answer 7

These enzymes; enterokinase, peptidases, sucrase, maltase and lactase, are bounded to the microvilli of the epithelial cells lining the villi of the small intestines

Question 8

Where does starch digestion begin in

Answer 8

Starch digestion begins in the mouth, where only a little starch is digested by salivary amylase into maltose
(Catalyses the hydrolysis of starch to maltose)

Question 9

What happens to carbohydrates that enter the small intestine

Answer 9

• The remaining starch is hydrolysed into maltose by pancreatic amylase
• Maltose is hydrolysed to glucose by maltase
• Lactose is hydrolysed to glucose and galactose by lactase
• Sucrose is hydrolysed to glucose and fructose by sucrase

Note: The end products of carbohydrate digestion are simple sugars (Monosaccharides)

Question 10

When does protein digestion start

Answer 10

It begins in the stomach

Question 11

What happens to polypeptides that reach the small intestine

Answer 11

The larger polypeptides that reach the small intestine are hydrolysed by trypsin to smaller polypeptides. The enzyme trypsin is produced as inactive trypsinogen in the pancreatic juice.
In the intestine, trypsinogen is converted to the active trypsin by intestinal enterokinase that is released into the intestinal lumen when the epithelial cells disintegrate
- The smaller polypeptides or peptides produced are further digested to amino acids (End-products), by peptidase

Question 12

How are emulsified fats broken down

Answer 12

Emulsified fats are hydrolysed by pancreatic lipase to fatty acids and glycerol (End-products of fat digestion)