Part -1 #NEET#AIIMS Digestion and Absorption|Types of Nutrition |Class 11th Topic|Biology•Zoology

Part -1 #NEET Digestion and Absorption||Class 11th Topic|Biology•Zoology
Key points for this Chapter
Digestion and Absorption
Contents
What is Digestion?
What are components of Digestive System?
Digestion and Absorption of Carbohydrates
Digestion and Absorption of Proteins
Describe the digestion and absorption of lipids in human beings
Digestion of Vitamins and Minerals
What is Appendix?
What is Reverse Peristalsis?
Diseases of the Digestive System

-What is Digestion?
-Digestion is a process of breakdown of complex food molecules into simple water: soluble molecules so that it can be easily absorbed by the body. Digestion is a catabolic process, that is, it is a breakdown process to release energy.
-There are two types of Digestion: Mechanical Digestion and Chemical Digestion.
Mechanical Digestion involves the physical breakdown of large food molecules into small molecules. Chemical Digestion involves breakdown of complex food molecules into small molecules in presence of digestive enzyme.
-What are components of Digestive System?
-Mouth is the first part of the Digestive System where the process of digestion begins. Mouth contain glands known as Salivary Glands. These salivary glands secrete an enzyme Salivary Amylase or Ptyalin that digests the carbohydrates such as starch into maltose (simple sugar).
-Pharynx is a part of the Digestive System as well as respiratory system. It pushes the food into the esophagus. A lid-like structure that covers the trachea or wind pipe at the time of swallowing of food is known as Epiglottis. It prevents the entry of food into the trachea. If food enters into the trachea, chocking may occur and this might also prove fatal.
-Esophagus is also known as food: pipe that passes the food to the stomach. The process of movement of food from the esophagus to stomach is known as Peristalsis. It is a muscular process.
-Stomach is the major part of the Digestive System where most of the digestion occurs. Stomach secretes the gastric juices which contain Hydrochloric Acid and sodium chloride. Hydrochloric Acid is secreted by gastric cells known as parietal cells. This acid is helpful in removing germs and pathogens. The environment of stomach is acidic due to hydrochloric acid. Stomach also produce an enzyme pepsinogen. Stomach also produces mucus that lubricates the stomach against hydrochloric acid.
-Small Intestine receives the partially digested food from the stomach. Small intestine is composed of 3 parts: Duodenum, Jejunum, Ileum. Here, carbohydrates, proteins and fats are digested. It receives the secretions from Pancreas and Liver. Some of the carbohydrates are also digested in small intestine with the help of Pancreatic Amylase.
-Large Intestine comprises of Cecum, Colon and Rectum. Cecum receives the food from the small intestine. Colon is a part where food is digested by gut flora. Water is majorly absorbed in this part. Rectum is the part from where the undigested food reaches the anus for excretion.

-Digestion and Absorption of Carbohydrates
Digestion of carbohydrates begins in the mouth with the help of an enzyme salivary amylase. It digests the starch into maltose. Rest of the digestion of carbohydrates occurs in small intestine with the help of the enzyme pancreatic amylase secreted by pancreas. The simplest form of carbohydrates is glucose. So all the carbohydrates consumed is finally converted into glucose for absorption.
-Digestion and Absorption of Proteins
Digestion of Proteins begins in the stomach. Stomach produce an enzyme Pepsinogen. Pepsinogen is an inactive form of enzyme pepsin. Inactive form of an enzyme is known as Zymogens. Pepsinogen is converted into pepsin by Hydrochloric Acid present in the stomach. Pepsin begins the process of digestion of proteins.
-Pancreas and Liver are two digestive glands that play an important role in the digestion. Pancreas secretes Trypsin and Chymotrypsin to digest proteins into small peptides. Other enzymes that participate in protein digestion are Carboxypeptidase and Proelastase. The simplest form of proteins is Amino acids in which they are absorbed by the body.
-Describe the digestion and absorption of lipids in human beings
Liver secretes bile that helps in digestion of fats (a form of lipid). The process of digestion of fats by bile is known as Emulsification of fats. Fat digestion is also promoted by lipase enzyme from the pancreas known as Pancreatic Lipase. The simplest form of fats are Fatty Acid and Glycerol. Lipase or bile breakdown fats into fatty acids and glycerol so that they can be absorbed by the body.
-Digestion of Vitamins and Minerals
Digestion of Vitamins and Minerals begins in the mouth. Further digestion of vitamins and minerals occurs in the small intestine where they are also absorbed and taken to the blood stream.