Enzymes in digestion

Question 1

What is an enzyme?

Answer 1

Enzymes are protein molecules made up of amino acids. These amino acids are joined together to from a long chain which is folded to produce a unique 3D structure.
An enzyme is a globular protein

Question 2

What is the role of a digestive enzyme?

Answer 2

They break down (hydrolyse) long food molecules, which are too big to digest, into smaller ones which can be absorbed

Question 3

What are the three different types of digestive enzyme?

Answer 3

Carbohydrase’s
Lipases
Proteases

Question 4

How do carbohydrates work as digestive enzymes? (amylase)

Answer 4

1. salivary and pancreatic amylase hydrolyses the alternate glycosidic bonds of starch into disaccharide maltose in the mouth and the small intestine.
2. The maltose is then hydrolysed into the monosaccharide a-glucose by a second enzyme called maltase, this is produced by the lining of the ileum.

Question 5

How do carbohydrates work as digestive enzymes? (sucrose)

Answer 5

1. sucrase hydrolyses the single glycosidic bond in the sucrose molecule into the two monosaccharides, glucose and fructose. it is secreted in the small intestine
2. lactose hydrolyses the single glycosidic bond in the lactose molecule into the two monosaccharides glucose and galactose. it is made in the small intestine

Question 6

How do lipases work as digestive enzymes?

Answer 6

• Lipids are hydrolysed by enzymes called lipases.
• Lipases are enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides.
• Lipids are split into tiny droplets called micelles by bile, salts which are produced by the liver.
• This process is called emulsification and increases the surface area of the lipids so that the action of lipases is quicker.

Question 7

How do proteases work as digestive enzymes?

Answer 7

• Proteins are large, complex molecules that are hydrolysed by a group of enzymes called peptidases.
• There are a number of different peptidases:
  1. Endopeptidases - they hydrolyse the peptide bond between amino acids in the central part of a protein
  2. Exopeptidase’s - hydrolyse the peptide bonds on the terminal amino acids of the protein formed by endopeptidases. This releases dipeptides and single amino acids
  3. Dipeptidases - hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane bound, being part of the cell-surface membrane of the epithelial cells lining the ileum.

Question 8

What is gastrin?

Answer 8

• Any of a group of digestive hormones secreted by the wall of the pyloric end of the stomach of mammals.
• It is released into the bloodstream when food enters the stomach and is carried by the circulatory system to the gastric cells in the stomach wall, which helps break apart fibrous matter in food and kills bacteria that may have been ingested.
• it also stimulates the release of bile

Question 9

What is mucus?

Answer 9

• viscous fluid that moistens, lubricates and protects many of the passages of the digestive and respiratory tract in the body.

Question 10

What is bile?

Answer 10

• made by the liver and stored in the gall bladder
• its main functions are creating the optimum pH for pancreatic enzymes to function in the small intestine
• it emulsifies fats into small droplets and increases surface area for lipase to work more efficiently