What it does
Food is mostly big molecules: starch, proteins and fats. The body can only take in small ones, so the gut breaks them down step by step with enzymes, then absorbs the small units into the blood. This page follows one meal on that journey. At each of seven stops (mouth, oesophagus, stomach, duodenum, small intestine, large intestine, rectum and anus) it lists the juices that pour in, the enzymes that act and what each one makes, the pH, and roughly how long the food stays there. Bars show how much of the meal’s starch, protein, fat and fibre is still whole, broken part-way, broken into small units, or already absorbed. To see why each enzyme needs the right temperature and pH, try the enzyme activity lab; and for the heart that pumps the absorbed food round the body, the cardiac cycle.
Using it
- Pick a Level. Class 10 lists the main juices and enzymes. Class 11 adds the extra enzymes (maltase, lactase, chymotrypsin, nucleases and more) and how inactive enzymes such as pepsinogen and trypsinogen are switched on.
- Pick a meal, or move the sliders to set your own grams of starch, protein, fat and fibre.
- Press Next stop, tap a numbered stop in the picture, or press Play the journey to watch the meal travel all the way.
- Read the card under the picture: the juices, the pH, the time and every enzyme at work. Then look at the bars to see what has changed.
What the bars mean
- Whole: the big molecules as eaten.
- Broken part-way: maltose from starch, peptides from protein, and fat in tiny droplets.
- Small units: glucose, amino acids, and fatty acids with glycerol.
- Absorbed: taken into the blood (or, for fats, into the lymph) through the villi of the small intestine.
Fibre has no bar colours except “whole”: humans make no enzyme that digests it, so it passes right through.
Worked example
Take Roti, dal and sabzi: 60 g starch, 18 g protein, 12 g fat and 10 g fibre. In the mouth, saliva turns 30 % of the starch into maltose, so 42 g of starch is still whole and 18 g is maltose. In the stomach, pepsin breaks 40 % of the protein into peptides: 7.2 g of peptides, 10.8 g of protein still whole. In the duodenum, bile and pancreatic juice act on everything, and in the rest of the small intestine the intestinal juice finishes the job and the villi absorb it, so the page shows 90 g of 100 g absorbed. The 10 g of fibre goes on to the large intestine, which takes back water, and leaves the body.
Where this fits in school
Class 10 science (life processes) covers nutrition in humans: the parts of the gut, the juices and enzymes, and absorption by villi. Class 11 biology (digestion and absorption) adds the full list of enzymes, how they are activated and how each kind of food is absorbed. This page is an independent learning aid. It is not made by or connected with NCERT, and it does not copy any textbook.
Questions
Are the numbers real? No. The shares broken down at each stop are round numbers chosen to show the idea. Real digestion depends on the food, how well it is chewed and the person. Times vary a lot too.
Why does starch stop being digested in the stomach? Salivary amylase works near neutral pH. The stomach’s acid stops it until the food reaches the alkaline duodenum, where pancreatic amylase takes over.
Is this medical advice? No. It is a teaching model of how digestion works.
Is anything saved? No. Nothing you choose is stored or sent anywhere.
Where the numbers come from
- The stops, juices and enzymes of human digestion: standard school biology, written by fibub in its own words.
- The share of each nutrient broken down at each stop, the meals and the times are made-up round values for teaching, labelled as such on the page.
- Checked in the tests by working each stop by hand and by checking that no food appears or disappears (mass balance).
- Drawings are fibub's own simple shapes. Nothing you enter is stored or sent anywhere.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.