Question

How do carbohydrates, proteins, and fats get digested in human beings?
A. They all are digested only in the stomach
B. They all are digested only in the small intestine
C. Carbohydrate digestion starts at the mouth. Protein and fat digestion start at the stomach and digestion of all three biomolecules complete at the small intestine.
D. None of the above.

Answer 1

Hint: The oral cavity is the first point of entry for the food into the digestive system and in the oral cavity, salivary amylase is the only digestive enzyme present. The stomach has pepsins and various types of enzymes act on the food in the small intestine.

Complete answer:
As a first step or start of the digestion process, the food is masticated in the mouth. Here, the saliva produced by the salivary gland gets mixed up with the food particles. Saliva contains an enzyme salivary amylase that converts the starch present in the food into the simple disaccharide, maltose sugar. So, carbohydrate digestion starts at the mouth. When the food reaches the stomach, HCL in the stomach activates some enzymes that digest proteins and also provides an acidic medium which is optimum for the enzymes to act properly. In the small intestine, complete digestion occurs with the help of enzymes from the pancreas, bile from the gallbladder, and also by the enzymes present in the intestinal juice itself.

Additional information
-Saliva is secreted from the parotid, the submandibular, and the sublingual glands present in our mouth.
-Saliva has mucus that will moisten the food and also will buffer the food ph. Additionally,
-The two-chief process in the mouth is the chewing and wetting action of the food provided by the teeth and the saliva. Both these processes will shape the food we eat into a mass known as a bolus. Bolus will be easily swallowed.
-The tongue will help in swallowing the bolus by moving it from our mouth to the pharynx.
The pharynx can either send the food to the lungs via the trachea or to the stomach via the esophagus.
-The closing of the epiglottis (a cartilaginous flap) in the tracheal opening prevents the food from entering into the trachea.
-The bolus will now enter the esophagus and eventually, it leads to the duodenum of the small intestine.
-In the small intestine, the pancreatic juice and bile will act. Eventually, by the enzymes in the succus entericus, the digestion of carbohydrates, proteins, and fats will be completed.

So, the correct answer is ‘Carbohydrate digestion starts at the mouth. Protein and fat digestion start at the stomach and digestion of all three biomolecules complete at the small intestine’.

The image represents the digestive system in the human body.
Note:
The carbohydrates get digested and get converted to monosaccharides such as glucose. Fats get digested into fatty acids and glycerol. Proteins are broken down into amino acids. The digested foods are absorbed in the body through the intestinal villi.