Role of Digestive Enzymes

Digestion

Digestion means a person's ability to digest food. Under this process food is treated with heat, enzymes, or a solvent to promote decomposition or to extract essential components from food. Under this process breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the bloodstream. During all these processing the digestive system/tract  plays a very crucial role. The digestive tract is a long tube-like structure that starts with the mouth and ends in the large intestine.

Apart from this there are so many digestive enzymes present in our digestive tract which help in the digestion process and make digestion easier. Digestive enzymes help in digestion of complex food into simpler form and these digestive enzymes are produced by different parts of the digestive tract.

There are mainly two main process if Digestion which happens in Mouth, They are:

  1. Mastication: this is done with the help of mouth, tongue and saliva.

  2. Lubrication of Food: under this process masticated food is converted into bolus with the help of salivary enzymes.


Different Types of Digestive Enzymes

There are mainly three main types of Digestive Enzymes present in our body. They’re grouped based on the reactions they catalyze:

  • Amylase Enzyme: They break down starches and carbohydrates into sugars.

  • Protease Enzyme: it breaks down proteins into amino acids.

  • Lipase Enzyme: It breaks down lipids, which are fats and oils, into glycerol and fatty acids.

  • Nuclease Enzyme: They break nucleic acid into nucleotides.


Function of Different Digestive Enzymes along with their Secretion Location

  1. Different Types of Digestive Enzymes produced inside the Mouth, They are:

  1. Lipase Enzyme: digestion of lipid is  initiated in the mouth.lipase starts the digestion of the lipids/fats.

  2. Salivary Amylase: digestion of carbohydrates  also initiated  in the mouth. Amylase, produced by the salivary glands, breaks complex carbohydrates to smaller chains, or even simple sugars. It is sometimes called ptyalin.

  3. Lysozyme: Food contains nonessential nutrients, e.g. bacteria or        viruses, it acts as an antimicrobial agent.

  1. Different Types of Digestive Enzymes produced inside Stomach, They are:

  1. Pepsin: It is the main gastric enzyme. It is produced by the stomach cells called "chief cells" in its inactive form  they are known as pepsinogen. Pepsinogen is then activated by the stomach acid into its active form, known as pepsin.

Function: It helps in breaking down protein in the food into smaller particles known as peptide and amino acids. First step of protein digestion occurs in the stomach, whereas digestion of carbohydrates and lipids starts in the mouth.   

  1. Gastric Lipase: It is an acidic lipase  secreted by the gastric chief cell in the fundic region of mucosa in the stomach. Optimum pH for gastric lipase is in between 3-6. 

Function: It is responsible for digestion of dietary fat present in our stomach.

  1. Hydrochloric Acid(HCL): It helps to denature the ingested protein and kill any bacteria and virus that remains in food, it also helps in activating pepsinogen to convert them into pepsin.

  2. Intrinsic Factor: It is produced by parietal cells of the stomach. It self in transformation and absorption of various micro nutrients.

  3. Mucin: It is highly acidic in nature and destroys different bacteria and viruses present in food.

  4. Gastrin: This hormone is produced by the G-cell of the stomach and it is mainly endocrine hormone. It stimulates parietal cells for HCL production and production of several intrinsic factors.

  1. Role of Pancreas in Digestion Process

Pancreas secretes pancreatic juice and this pancreatic juice contain various digestive enzymes, They are:

  1. Trypsinogen: they are present in inactive form, once they are activated they are converted into trypsin, which help in breakdown of protein. Trypsinogen is activated with the help of enterokinase enzyme.

  2. Chymotrypsinogen: It is present in inactive form and with the help of enterokinase it is converted into active chymotrypsin.

  3. Carboxypeptidase: It is a protease that takes the terminal amino acid group from protein.

  4. Pancreatic Lipase: It degrades triglycerides into two fatty acids and a monoglyceride. 

  5. Cholecystokinin: It is a unique peptide released by duodenal I- cell, they are also produced in response to chyme containing high fat.

  1. Enzymes produced by Small Intestine

There are various digestive enzymes which are produced by small intestine, they are:

  1. Secretin: It is an endocrine hormone produced by the duodenal S type cell in response to decrease acidity of gastric chyme.

  2. Cholecystokinin (CCK): It  is a unique peptide released by the duodenal "I cells" in response to chyme containing high fat or protein content. It also increases gallbladder contraction, causing release of pre-stored bile into the cystic duct, and eventually into the common bile duct and via the ampulla of vater into the second anatomic position of the duodenum.

  3. Gastric Inhibitory Peptide (GIP): It is a kind of peptide that decreases gastric motility and is produced by duodenal mucosal cells.

 

Multiple Choice Questions

  1. Which of the following matches between Digestive Enzyme and Molecule Digested is incorrect?

  1. Protease - Peptide

  2. Amylase - Carbohydrate

  3. Lipase - Fats

  4. Amylase - Starches

Answer: (2)

  1. Which of the following statements about the location of Digestive Enzymes is true?

  1. The majority of digestive enzymes' work is done in the small intestine

  2. Proteases are found only in the stomach

  3. Most digestive enzymes are produced in the small intestine

  4. The pancreas is part of the alimentary canal, and the source of many digestive enzymes.

Answer: (2)

FAQ (Frequently Asked Questions)

1. What are Digestive Enzymes?

Digestive Enzymes present in our digestive tract which help in the digestion process and make digestion easier. Digestive enzymes help in digestion of complex food into simpler form and these digestive enzymes are produced by different parts of the digestive tract.

 2. Explain four types of Cell present in the Stomach?

  1. Parietal Cell: this type of cells Produce hydrochloric acid and several  intrinsic factors.

  2. Gastric Chief Cell: They  Produce pepsinogen. Chief cells are mainly found in the body of the stomach. 

  3. Mucous Cell: They Produce mucin and bicarbonate to create a "neutral zone" to protect the stomach lining from the acid or irritants in the stomach chyme.

  4. G Cell: They Produce the hormone gastrin in response to distention of the stomach mucosa or protein, and stimulate parietal cell production of their secretion.