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Life processes is the longest biology chapter in Class 10, and it is easy to drown in labels: villi, alveoli, nephrons, xylem, phloem. Students who do well usually learn it as a set of journeys rather than a list of organs. Where does the glucose come from, where does it go, and what carries it? This post gives you those journeys, a worked set of answers, the mistakes examiners see most often, and a routine to fix them.
What does the syllabus include?
The CBSE Class X Science syllabus for 2026-27 lists "'Living Being'. Basic concept of nutrition, respiration, transport and excretion in plants and animals" under Unit II, World of Living, which carries 25 of the 80 theory marks. Two practicals come from this chapter: preparing a leaf peel to show stomata, and showing that carbon dioxide is given out during respiration. Everything below is from Chapter 5 of the NCERT Class 10 Science textbook. Check the current syllabus for your year.
Where do plants get their food from?
Plants make their food. In photosynthesis, carbon dioxide and water are converted into carbohydrates using sunlight absorbed by chlorophyll, and oxygen is released. A balanced summary is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. NCERT breaks it into three events: light is absorbed by chlorophyll; light energy becomes chemical energy and water is split; carbon dioxide is reduced to carbohydrate. Carbon dioxide enters through stomata, which guard cells open and close.
This is harder to believe than it sounds. Messig and Groß (2018) studied high-school students' ideas about plant nutrition and found that many reasoned about plants using ideas from human eating, such as food being taken in from outside. Showing students the classic van Helmont experiment, in which a willow gained weight while the soil barely changed, did not change their view; it reinforced their earlier ideas. So if your gut feeling is "plants eat from the soil", say the correct version aloud until it feels natural: minerals and water come from the soil, food is made in the leaf.
What happens to glucose during respiration?
NCERT's Figure 5.8 shows three pathways. All start the same way: in the cytoplasm, glucose (six carbons) is broken into pyruvate (three carbons).
In yeast, without oxygen: pyruvate becomes ethanol and carbon dioxide. This is fermentation, a kind of anaerobic respiration.
In mitochondria, with oxygen: pyruvate becomes carbon dioxide and water, releasing far more energy. This is aerobic respiration.
In our muscles, short of oxygen: pyruvate becomes lactic acid, and its build-up during sudden activity causes cramps.
The energy released is used to make ATP, which NCERT calls the energy currency of the cell.
How are materials transported and wastes removed?
In humans, the heart has four chambers, which keeps oxygenated and deoxygenated blood apart. Blood passes through the heart twice in each circuit of the body, which NCERT calls double circulation. Haemoglobin in red blood cells carries oxygen. In plants, xylem moves water and minerals up from the roots, helped by the pull of transpiration, and phloem moves food, using energy from ATP. NCERT calls this movement of food translocation.
For excretion, each kidney contains many nephrons. Blood is filtered in Bowman's capsule, and useful substances such as glucose, amino acids, salts and most of the water are reabsorbed along the tubule.
A worked example. NCERT says the initial filtrate in a healthy adult is about 180 litres a day, while only a litre or two is excreted as urine. What fraction is reabsorbed? If 2 litres are excreted, 178 litres are reabsorbed, and 178 ÷ 180 ≈ 0.99. So about 99 per cent of the filtrate goes back into the blood. That is why NCERT stresses re-absorption, and why dialysis, which has no re-absorption step, works differently from a kidney.
Which mistakes come up most often?
Saying respiration is breathing. Breathing moves air in and out; respiration releases energy from food inside cells.
Saying only animals respire. Plants respire all the time, day and night.
Putting the first step of respiration in the mitochondria. Glucose is broken to pyruvate in the cytoplasm.
Mixing up xylem and phloem. Xylem carries water and minerals; phloem carries food.
Calling fish circulation double. In fish, blood passes through the two-chambered heart only once per circuit.
A practice routine for this chapter
Draw the three respiration pathways from Figure 5.8 from memory, with where each happens.
Trace one oxygen molecule from your nostrils to a muscle cell in five lines: nostrils, lungs and alveoli, blood and haemoglobin, heart, tissues.
Trace one water molecule from the soil to the air through a plant: root, xylem, leaf, stomata.
Label the nephron, heart and digestive system diagrams with the book closed, then correct them in a different colour. Our guide on drawing the diagram first explains why this helps.
If a process such as double circulation is hard to picture from a still diagram, seeing it move can help. The Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read.
Pick one journey from this post today and write it out in five lines without the book.
