The complete digestion of carbohydrates, proteins and fats occurs in

The small intestine is the primary site for the complete chemical digestion of all major macronutrients: carbohydrates, proteins, and fats [1]. While digestion begins in the mouth (carbohydrates) and stomach (proteins), it is only in the small intestine that these substances are fully broken down into their simplest absorbable forms [1]. This process is facilitated by secretions from the liver (bile) and the pancreas (pancreatic juice), as well as intestinal enzymes [2]. Bile emulsifies fats into smaller globules to increase enzyme efficiency, while pancreatic and intestinal juices contain proteases, amylases, and lipases that finalize the breakdown of proteins into amino acids, carbohydrates into glucose, and fats into fatty acids and glycerol [2]. Once digestion is complete, the small intestine also serves as the main site for nutrient absorption into the bloodstream [3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.3 > p. 86
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > Small Intestine > p. 126
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > In a Nutshell > p. 134