Absorption of Digested Food

The digestive system is a special set of organs that help break down the food we eat into smaller composite particles, that are then absorbed into the bloodstream. Proteins called digestive enzymes aid the process and help to catalyse a series of chemical reactions. Before we proceed, let's learn what is meant by digestion. 

Digestion is a complex physicochemical process that transforms large particles of food into smaller, simple substances. This is followed by the absorption and assimilation of digested food that begins with the walls of the alimentary canal.

Absorption in Digestion

The process by which digested food molecules are absorbed into the bloodstream and transported to different parts of the body is known as absorption. Absorption of food begins with the small intestine. The digested food molecules pass through the walls of the small intestine and then into the bloodstream.

Once the food particles reach the bloodstream, they are transported throughout the different parts of the body, wherever necessary. 

Only smaller, soluble food molecules can pass through the walls of the small intestine, whereas larger food molecules cannot pass through as they are insoluble.

Mechanism of Absorption 

During the absorption process in digestion, a network of mucous membranes help carry the digested, soluble food molecules into the bloodstream or lymph. The process of absorption involves the following steps.

  • Diffusion

  • Active Transport

  • Facilitated Transport

  • Passive Transport

Let us revise a few important concepts with the following exercise.

Pop Quiz 1

  1. The absorption of food takes place in the ___________.

  1. Large intestine

  2. Mouth

  3. Small intestine

  4. None of the above

Diffusion

The movement of solute particles from a region of their higher concentration to a region of their lower concentration through a permeable membrane is known as simple diffusion.

Through this process, monosaccharides like glucose, ions like fluoride and chlorides and amino acids are transported into the bloodstream, on the basis of the concentration gradient between the membranes. This is the first step in the mechanism of absorption of digested food.

Active Transport

The process by which solute particles move from a region of lower concentration to a region of higher concentration using energy, such as ATP, is known as active transport. Active transport helps electrolytes such as Na+ ions to diffuse into the bloodstream, against the concentration gradient.

Facilitated Transport

It is the active movement of solute particles across a permeable biological membrane, that is aided by specific groups of carrier proteins. Facilitated transport helps to carry digested molecules like amino acids, sugars and glucose into the bloodstream.

Passive Transport 

The movement of solute particles across a permeable cell membrane without using any energy is known as passive transport. This is the final step in the absorption of food. Post digestion, simple and soluble food particles are absorbed into the bloodstream through the process of passive transport. 

Digested molecules like glycerol and fatty acids cannot be absorbed into the bloodstream. These molecules then attach to tiny droplets called micelles or micellar bodies. These complexes further transform into chylomicrons. Chylomicrons are small globules of fat that are coated by proteins.

The chylomicrons are then carried into lymph vessels, and they then pass on all the digested food particles into the blood. These digested and absorbed food particles are transported to various cells and tissues so that they can be utilised again. This last step is known as the assimilation of digested food.

The following points help illustrate the importance of absorption.

  1. The body needs to extract ingredients from the food you eat to ensure its proper functioning.

  2. As food particles break down into smaller particles, the process of absorption ensures that these particles are carried into the bloodstream.

  3. It is only through the process of absorption that digested food particles reach various cells, tissues and organs of our body.

  4. Blood carries nutrients like sugars and amino acids from the absorbed food into the liver where they are processed.

  5. From the liver, these nutrients are delivered to other parts of the body where they are required.

For more on absorption definition in biology and related processes, refer to our free PDF notes, practice papers and revision notes, available on the website. Install the Vedantu app today, and have your doubts instantly clarified.

FAQ (Frequently Asked Questions)

1. What is absorption?

The process by which digested food molecules are absorbed into the bloodstream and transported to different parts of the body is known as absorption.

2. Where is digested food absorbed into the blood in the human body?

The absorption of food begins with the small intestine. The digested food molecules pass through the walls of the small intestine and then into the bloodstream.

3. What is absorption in biology?

The process by which digested food molecules are absorbed into the bloodstream and transported to different parts of the body is known as absorption.

4. What is the definition of digestion?

Digestion is a complex physicochemical process that transforms large particles of food into smaller, simple substances.