BlogNEETDigestion and Absorption

Digestion and Absorption

Digestion is the straightforward act of breaking down food molecules into smaller components, as we’ve taught. This procedure starts in the mouth and continues via the stomach, small intestine, large intestine, and finally the anus. This is how digestion works on a physical level. Let’s take a closer look at the chemical process of digestion that occurs when biomolecules are digested.

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    What is Digestion?

    The process of digestion involves breaking down large, insoluble food molecules into smaller molecules that may be absorbed into the bloodstream. Many digestive fluids and enzymes are used in this process, including saliva, mucus, bile, and hydrochloric acid, among others.

    The human body’s food digestion process is divided into four stages:

    • Food enters the body through the mouth, travels into the stomach, and then into the small intestine, where it is digested.
    • Through microscopic holes in the small intestine, nutrients from digested food are absorbed into the bloodstream.
    • The undigested meal is transferred to the large intestine, where any unprocessed water or nutrients are reabsorbed.
    • The remaining waste food product is discarded.

    What is the function of the digestive system?

    Your digestive system is built specifically to convert your food into the nutrients and energy you require to live. When that’s done, it neatly wraps your solid waste, or stool, for disposal the next time you have a bowel movement.

    What is the significance of digestion?

    Your body requires nutrients from the food you consume and the liquids you drink to keep healthy and perform correctly. Carbohydrates, proteins, lipids, vitamins, minerals, and water are all nutrients. Your digestive system breaks down and absorbs nutrients from the food and liquids you consume so that they may be used for vital functions such as energy, cell growth, and cell repair.

    Mechanism of Digestion

    When food enters the mouth, it is mechanically digested by mastication (chewing) and also becomes when it comes into contact with saliva. Saliva contains salivary amylase, a digestive enzyme that begins the digestion of starch in meals.

    The food will be in the form of a tiny, circular slurry mass called a bolus after it has been masticated and starch digested. The motion of peristalsis transports it down the esophagus and into the stomach.

    Gastric fluids kick-start protein digestion in the stomach. Pepsin and hydrochloric acid are the most common ingredients in these juices. Because the HCl may cause damage to the stomach wall, the stomach secretes mucus, which forms a sticky covering that protects the stomach from the acid’s harmful effects.

    Protein digestion occurs simultaneously thanks to peristalsis, which allows the quantity of food to combine with the digestive enzymes. After some time, a thick liquid called chyme is created, which enters the duodenum, where it interacts with pancreatic digestive enzymes and liver bile juice before passing through the small intestine. The chyme gets taken into the bloodstream when it has been thoroughly digested.

    It’s worth noting that the small intestine is responsible for 95% of nutrient absorption. In the large intestine, where the pH is slightly acidic, water and minerals are reabsorbed back into the circulation. Some vitamins generated by bacteria in the colon, such as vitamin K and biotin, are also taken into the bloodstream in the colon. During feces, waste material exits the rectum.

    Disorders of the Digestive System

    Inflammation of the intestine is caused by a variety of bacterial, protozoan, parasitic, and viral infections. Jaundice, vomiting, diarrhoea, constipation, indigestion, and other conditions are prevalent.

    Malnutrition-related diseases are especially widespread in developing and impoverished countries.

    • Protein Energy Malnutrition (PEM): In babies and toddlers, Protein Energy Malnutrition (PEM) causes Marasmus and Kwashiorkor.
    • Marasmus: Marasmus is caused by a lack of protein and calories in the diet. Leg thinning, acute emaciation, dry and wrinkled skin and mental impairment are all symptoms of this illness.
    • Kwashiorkor: Kwashiorkor is caused by a protein deficit. Muscles are dying away, yet there is still some fat beneath the skin. Swelling and severe edema of body parts characterize the disorder.


    The process of absorbing or assimilating chemicals into cells or across tissues and organs via diffusion or osmosis is known as absorption. The bio-macromolecules are broken down in the duodenum and absorbed in the jejunum and ileum of the gut. The undigested food travels to the big intestine, where it absorbs some water and minerals.

    • Food is absorbed through diffusion due to a concentration gradient or through aided transport by a carrier protein.
    • The osmotic gradient is what transports water.
    • Active transport against the gradient is used to absorb amino acids, glucose, monosaccharides, and Na+ in the blood.
    • Micelles form chylomicrons (protein-coated fat globules) that are carried into the villi’s lacteals (lymph vessels) and discharged into the bloodstream.

    Varied areas of the body absorb different amounts of nutrients, with the small intestine absorbing the most.

    • Medications for the mouth
    • Water, simple carbohydrates, and alcohol in the stomach
    • Maximum absorption occurs in the small intestine.
    • Water and minerals in the large intestine

    Assimilation is the process by which an absorbed nutrient travels through the bloodstream and lymphatic system to various parts of the body for use.

    Carbohydrate Digestion and Absorption

    Carbohydrates are an important ingredient in human nutrition. Sugar and starch are the two forms of carbohydrates that the human digestive system can process.

    The small intestine and three enzymes found in the mouth, Lactase, Sucrase, and Maltase, break down sugar in the gastrointestinal tract.

    In the same way, starch is broken down by Amylase enzymes found in the mouth and stomach. Carbohydrates are absorbed in the small intestine with the help of Villi, which are tiny finger-shaped projections. In addition, see: Carbohydrates

    Carbohydrate digestion begins chemically in the mouth. The flowchart below depicts the set of stages required in breaking down carbs into monomers in detail.

    Digestion and Absorption of Proteins

    Proteins are essential for bodily cell and tissue growth and replenishment. Protein digestion occurs in the stomach with the help of protease and pepsin enzymes, which break down proteins into amino acids. The presence of hydrochloric acid in the stomach aids the process. Amino acids are small molecules that are taken into the bloodstream through the small intestinal wall.

    Digestion and Absorption of Lipids

    Lipids are insoluble in water chemical molecules made up of fatty acids. Lipids are most commonly found as fats. Because lipids are insoluble, digestion and absorption of fats is a difficult process.

    Fats stay together as a big glob of insoluble substance after reaching the stomach because they are hydrophobic. Bile juice, which contains bile salts, is used to break it down. Pancreatic lipase, the body’s main fat-absorbing enzyme, subsequently acts on these broken molecules. Pancreatic lipase degrades fats into free fatty acids and monoglycerides, which are small enough to pass past the small intestine and into the bloodstream.

    Food is an essential component of any live organism’s sustenance and growth. Humans have evolved specific systems for converting food into energy and distributing it to all of the body’s cells. From the mouth to the anus, the human digestive system is made up of a succession of interrelated organs.

    Also read: ATP Adenosine Tri-Phosphate


    What exactly is digestion?

    Digestion is the mechanical and biological process of reducing complex food molecules into simpler compounds that may be absorbed.

    What is the purpose of bile?

    The liver produces bile, which is a dark yellowish-green or brown fluid that is stored in the gallbladder. It is made up of water and organic molecules such as bile acids, lipids, bilirubin, and cholesterol.

    Describe the elimination process.

    The last stage of digestion is elimination. Food residues that cannot be digested or absorbed are expelled or egested from the body as semi-solid faeces during this procedure.

    Where does the digestive process take place?

    The digestive process starts in the mouth and continues to the stomach, small intestine, large intestine, and finally the anus.


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