Quick Guide To The Differences Between Chemical And Mechanical Digestion

The topic of digestion is often overlooked in discussions on healthy living. However, proper digestion and regular bowel movements are essential for good health. The gastrointestinal tract plays a vital role in the body’s overall well-being by helping to absorb nutrients and get rid of waste products. If your system does not work correctly, you may experience abdominal cramps, bloating, gas and diarrhea.

Digestion is the breakdown of large food molecules into small ones. It can be divided into two categories based on how they are broken down: chemical digestion and mechanical digestion. Today, we shall briefly see what these two types of digestion are and how they differ.

Mechanical Digestion

Breakdown of the food particles mainly done by your teeth is termed mechanical digestion. While talking about mechanical digestion, you might be confused that this type of digestion only occurs in your mouth. Still, the scope of mechanical digestion does not limit to your mouth but is continued throughout the whole digestive tract. For example, all these mentioned events are mechanical digestion.

â— Chewing by teeth in your mouth

â— Churning of food in the stomach

â— Further segmentation in the small intestine

The initial breakdown of food happens in the mouth due to the grinding action of teeth. It’s also known as mastication or chewing. The tongue then pushes the mechanically processed food as a bolus into the throat.

The food is passed through the whole digestive tract through a process called Peristalsis, a wave of contraction and relaxation of smooth circular and longitudinal muscles of the digestive tract.

Chemical Digestion

Chemical digestion is a term used to convert food into energy, which takes place inside the cells of our body. The primary purpose of chemical digestion is to break down large molecules such as carbohydrates, lipids, and proteins into smaller ones and release their energy in ATP (adenosine triphosphate).

Chemical digestion starts in the mouth when teeth are used for chewing and mixing with saliva. Saliva contains amylase, an enzyme that helps break down starch into simple sugars.

Chemical digestion is governed by different chemical substances present in the digestive tract, i.e., enzymes, acids, and bile. These are secreted in the lumen of the digestive system through other body processes such as salivary glands, pancreas, and stomach.

â— The digestion of carbohydrates (mainly starch and glycogen) present in our food is done through an enzyme known as amylase, primarily secreted by salivary glands and the pancreas.

â— Another enzyme, called Protease, digests proteins and converts them into smaller polypeptide chains which are further digested to amino acids by secretions of the pancreas.

â— Lipids are also digested in the digestive system through bile which emulsifies lipids.

â— Also, the nucleic acid content present in the foods is digested by the action of several nucleases, which are secreted through your pancreas.

Dissimilarities of Mechanical and Chemical Digestion

Mechanical digestion breaks down food into digestible bits, which is primarily accomplished by the teeth. In contrast, chemical digestion is the process of breaking down high molecular weight chemicals in food into little ones that the body may easily absorb.

â— The mouth plays a vital role in mechanical digestion, and however, most of the chemical digestion takes place in the stomach.

â— The surface area available for enzymatic reactions for chemical digestion rises by mechanical digestion. On the other hand, chemical digestion improves nutrient absorption by breaking down large molecules into smaller ones.

Similarities Between Mechanical and Chemical Digestion

In contrast to dissimilarities, both of these types of digestion may also have some similarities.

â— Animals’ digestion, absorption, and elimination of ingested food are aided by mechanical and chemical digestion.

â— The stomach plays an essential role in both mechanical and chemical digestion.


While mechanical digestion is the physical breakdown of food through chewing, chemical digestion involves the actions of enzymes that break down food into smaller molecules for absorption by the small intestine. Visit MARHAM.PK now to schedule your consultation with a Gastroenterologist today if you face any problem regarding your gastrointestinal tract (GI Tract) or give a routine checkup. We have the best available Gastroenterologist for you!

Frequently Asked Questions (FAQs)

1- Why do we require both chemical and mechanical digestion?

The digestion process could not be possible if either chemical or mechanical digestion fails to be carried out correctly. To have your food fully digested, it is necessary to keep this functioning properly.

2- Which type of digestion starts earlier?

Mechanical digestion starts earlier than chemical digestion to break down pieces of food into tiny particles for the effective working of enzymes present in saliva.

3- Does mechanical digestion occur in the small intestine?

Mechanical digestion takes place in the small intestine as well. This is known as segmentation, comprising localized segmentation contractions of mainly circular muscles of the small intestine.

4- What is the role of water in chemical digestion?

Water plays an essential role in chemical digestion, thus termed hydrolysis to break down complex food particles, which otherwise is very slow.