Defence
Which is the first enzyme to mix with food in the human digestive tract?
Answer (Detailed Solution Below)View answer ▾Hide ▴
Answer: Option C — Salivary amylase (ptyalin)
Detailed Solution
Digestion begins in the mouth. As we chew food, it is mixed with saliva, secreted by three pairs of salivary glands: the parotid (the largest, near the ears), submandibular and sublingual glands. An adult produces about 1-1.5 litres of saliva a day.
Saliva contains the enzyme salivary amylase, also called ptyalin. It is the first enzyme to act on food. It begins the digestion of starch (a complex carbohydrate), breaking it down into maltose (a simpler sugar) and dextrins. This is why a piece of chapati or bread starts to taste slightly sweet when chewed for a long time. Saliva works best at a nearly neutral pH (about 6.8). Once the food reaches the acidic stomach, salivary amylase stops working. Saliva also contains mucus, which moistens and lubricates food, and lysozyme, which kills some bacteria.
The process of digestion continues along the tract:
Stomach: gastric glands secrete hydrochloric acid, which kills germs and provides an acidic medium, and pepsin, which begins protein digestion. In infants, rennin helps curdle milk.
Small intestine (duodenum): bile from the liver emulsifies fats. Pancreatic juice contains pancreatic amylase (starch), trypsin (proteins) and lipase (fats).
Small intestine (ileum): intestinal juice completes the digestion of carbohydrates into glucose, proteins into amino acids, and fats into fatty acids and glycerol. Digested food is absorbed through finger-like villi into the blood and lymph.
Large intestine: water and salts are absorbed, and undigested waste is removed.
The small intestine is the site of the complete digestion of carbohydrates, proteins and fats. It is the longest part of the alimentary canal, about 6-7 metres long.
Enzymes are biological catalysts, usually proteins, that speed up chemical reactions in the body without being used up.
Why not the other options?
- ✗Pepsin acts in the stomach on proteins.
- ✗Trypsin acts in the small intestine on proteins.
- ✗Lipase acts in the small intestine on fats.
Quick tip
Remember: Digestion starts in the mouth with salivary amylase (ptyalin: starch to maltose); pepsin in the stomach; trypsin, lipase and pancreatic amylase in the small intestine (site of complete digestion).
💬 Discussions on this question
Ask a doubt ›Still stuck on this question? Ask our faculty and fellow students — answers appear here.
Ask a doubtMore Nutrition, Vitamins & Digestion Questions
View all ›- Q1.Which vitamin helps the human body absorb and use calcium for bones and teeth?
- Q2.Bile juice, which is stored in the gall bladder, is secreted by the:
- Q3.Which vitamin helps prevent major birth defects of the brain and spine (neural tube defects) in newborn babies?
- Q4.Night blindness and xerophthalmia are caused by the deficiency of:
More General Knowledge Questions
- Q1.The techniques of Rasa and Bhava used in Indian classical dance trace their origin to which ancient text?Indian Dance Forms
- Q2.Lavani, Powada, Koli, Waghya Murali and Dhangari Gaja are folk dances of which state?Indian Dance Forms
- Q3.The one-act play associated with the Sattriya tradition of Assam is called:Indian Dance Forms
- Q4.Which dance form of Goa is known as the 'Warrior Dance'?Indian Dance Forms
- Q5.Manipuri dance is based on the Rasleela themes of:Indian Dance Forms
Nutrition, Vitamins & Digestion — Preparation
This question tests your understanding of Nutrition, Vitamins & Digestion, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers human nutrition: carbohydrates, proteins, fats, vitamins and minerals, their sources and the diseases caused by their deficiency, balanced diet, and the human digestive system with its organs, glands and enzymes. Exam questions frequently ask which deficiency causes which disease (scurvy from lack of vitamin C, rickets from vitamin D, night blindness from vitamin A and beriberi from vitamin B1), the chemical names of vitamins, and where each nutrient is digested. The liver is the largest gland in the human body and produces bile. Practise the nutrition, vitamins and digestion questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.