Digestive enzymes types functions and mechanism of action in 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 the digestion of complex food into simpler forms and these digestive enzymes are produced by different parts of the digestive tract.
There is Mainly Two Process of Digestion Which Happen in Mouth, They are:
Mastication: this is done with the help of mouth, tongue and saliva.
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 catalyse:
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
Different Types of Digestive Enzymes produced inside the Mouth, they are:
Lipase Enzyme: digestion of lipids is initiated in the mouth lipase starts the digestion of the lipids/fats.
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.
Lysozyme: Food contains nonessential nutrients, e.g. bacteria or viruses, it acts as an antimicrobial agent.
Different Types of Digestive Enzymes are Produced Inside Stomach, they are:
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.
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.
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.
Intrinsic Factor: It is produced by parietal cells of the stomach. Itself in transformation and absorption of various micronutrients.
Mucin: It is highly acidic in nature and destroys different bacteria and viruses present in food.
Gastrin: This hormone is produced by the G-cell of the stomach and it is mainly an endocrine hormone. It stimulates parietal cells for HCL production and production of several intrinsic factors.
Role of Pancreas in Digestion Process
Pancreas secretes pancreatic juice and this pancreatic juice contain various digestive enzymes, they are:
Trypsinogen: they are present in inactive form, once they are activated they are converted into trypsin, which helps in breakdown of protein. Trypsinogen is activated with the help of enterokinase enzyme.
Chymotrypsinogen: It is present in inactive form and with the help of enterokinase it is converted into active chymotrypsin.
Carboxypeptidase: It is a protease that takes the terminal amino acid group from protein.
Pancreatic Lipase: It degrades triglycerides into two fatty acids and a monoglyceride.
Cholecystokinin: It is a unique peptide released by duodenal I- cells, they are also produced in response to chyme containing high fat.
Enzymes Produced by Small Intestine
There are various digestive enzymes which are produced by small intestine, they are:
Secretin: It is an endocrine hormone produced by the duodenal S type cell in response to decreased acidity of gastric chyme.
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.
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?
Protease - Peptide
Amylase - Carbohydrate
Lipase - Fats
Amylase - Starches
Answer: (2)
2. Which of the following statements about the location of Digestive Enzymes is true?
The majority of digestive enzymes' work is done in the small intestine
Proteases are found only in the stomach
Most digestive enzymes are produced in the small intestine
The pancreas is part of the alimentary canal, and the source of many digestive enzymes.
Answer: (2)
Interesting Facts
As you grow older, the enzyme production in your body tends to decrease.
Your lifestyle and the type of diet you consume regularly makes a lot of difference with regard to the digestive enzymes in your body.
One of the best ways to keep your digestive tract in shape is through engaging in aerobic exercises on a regular basis.
Besides breaking down the food into various nutrients in your body, digestive enzymes also help to fight off certain bacterias and diseases.
FAQs on Role of Digestive Enzymes in Human Digestion Process
1. What are digestive enzymes?
Digestive enzymes are biological catalysts that break down large food molecules into smaller, absorbable units during digestion. They speed up chemical reactions in the digestive system without being consumed.
- Convert carbohydrates into simple sugars
- Break proteins into amino acids
- Split fats (lipids) into fatty acids and glycerol
- Enable nutrients to be absorbed through the small intestine
2. What is the role of digestive enzymes in digestion?
The role of digestive enzymes is to chemically break down complex food molecules into simpler forms that the body can absorb and use. Without these enzymes, most nutrients would remain too large to pass through the intestinal wall.
- Hydrolyze food using hydrolysis reactions
- Convert macromolecules into absorbable units
- Support nutrient absorption in the small intestine
- Increase efficiency and speed of digestion
3. Where are digestive enzymes produced in the body?
Digestive enzymes are produced mainly in the salivary glands, stomach, pancreas, and small intestine. Each organ releases specific enzymes for different nutrients.
- Salivary glands: secrete salivary amylase
- Stomach: secretes pepsin
- Pancreas: releases pancreatic amylase, lipase, and proteases
- Small intestine: produces maltase, sucrase, lactase, and peptidases
4. How do digestive enzymes work?
Digestive enzymes work by binding to specific food molecules at their active site and lowering the activation energy of chemical reactions. This allows large molecules to be split efficiently.
- Form an enzyme-substrate complex
- Break chemical bonds through hydrolysis
- Release smaller products
- Remain unchanged and reusable after the reaction
5. What are the main types of digestive enzymes?
The main types of digestive enzymes are amylases, proteases, and lipases, each targeting a specific macromolecule. These enzymes ensure complete digestion of carbohydrates, proteins, and fats.
- Amylases: break starch into maltose and glucose
- Proteases (e.g., pepsin, trypsin): break proteins into amino acids
- Lipases: break fats into fatty acids and glycerol
6. Why are digestive enzymes important for nutrient absorption?
Digestive enzymes are important because only small, soluble molecules can be absorbed through the intestinal villi into the bloodstream. Large macromolecules cannot pass through the intestinal lining.
- Convert starch into glucose
- Convert proteins into amino acids
- Convert lipids into fatty acids and glycerol
- Enable transport into blood or lymph
7. What happens if the body lacks digestive enzymes?
If the body lacks digestive enzymes, food is not properly digested, leading to malabsorption and digestive disorders. Nutrients remain undigested and may cause discomfort.
- Causes bloating and diarrhea
- Leads to nutrient deficiencies
- Example: lactose intolerance due to lack of lactase
- May require enzyme replacement therapy
8. What is the difference between mechanical and chemical digestion?
Mechanical digestion physically breaks food into smaller pieces, while chemical digestion uses digestive enzymes to chemically break down molecules. Both processes work together in digestion.
- Mechanical digestion: chewing and stomach churning
- Chemical digestion: enzyme action and acid breakdown
- Chemical digestion changes molecular structure
- Mechanical digestion increases surface area for enzymes
9. How does the pancreas help in digestion?
The pancreas helps in digestion by secreting pancreatic juice containing key digestive enzymes into the small intestine. These enzymes act on carbohydrates, proteins, and fats.
- Releases pancreatic amylase for starch digestion
- Releases trypsin and chymotrypsin for protein digestion
- Releases pancreatic lipase for fat digestion
- Secretes bicarbonate to neutralize stomach acid
10. Can you give examples of digestive enzymes and their substrates?
Examples of digestive enzymes include amylase, pepsin, and lipase, each acting on a specific substrate during digestion. Enzyme specificity ensures efficient breakdown of nutrients.
- Amylase → acts on starch
- Pepsin → acts on proteins
- Lipase → acts on triglycerides
- Lactase → acts on lactose
