This MCQ module is based on: Photosynthesis — How Plants Make Food
TOPIC 35 OF 46
Photosynthesis — How Plants Make Food
🎓 Class 7
Science
CBSE
Theory
Ch 10 — Life Processes in Plants
⏱ ~14 min
🌐 Language: [gtranslate]
🧠 AI-Powered MCQ Assessment
▲
Myaischool Lt Science Assessment
▲
[myaischool_lt_science_assessment grade_level="class_7" science_domain="biology" difficulty="basic"]
Meera's Question in the Kitchen Garden
One Sunday morning, Meera was helping her mother water the spinach patch behind their house in Patna. As she tilted the watering can, she thought about her school tiffin — a stuffed paratha, a banana, and some boiled moong. "Amma," she said, "I eat food that comes from plants. But where do plants get their food from? Nobody feeds them!" Her mother smiled and pointed at the bright green leaves glistening in the sunlight. "Look carefully. These leaves are their tiny kitchens."
Think first: A small sapling becomes a huge tree over many years. Where does all that extra wood, bark and leafy tissue come from? It cannot come from the mouth (plants don't have one), so it must be built from something the plant takes in from its surroundings. What do you think those ingredients are?
10.1 Autotrophs — The Self-feeders
Living things can be sorted by how they get their food. Green plants, certain algae and a few bacteria make their own food from simple substances in their surroundings. They are called autotrophs. Animals, fungi and most bacteria cannot build food from sunlight and air; they must eat other organisms. These are called heterotrophs.
Nutrition in plants: The process by which plants take in simple raw materials from the soil and air and turn them into complex, energy-rich food is called plant nutrition. The special method green plants use is called photosynthesis.
10.2 Photosynthesis — Food from Sunlight
The word photosynthesis comes from two Greek roots: photo (light) and synthesis (putting together). It is the process in which green plants use sunlight to put together carbon dioxide from the air and water from the soil to form a sugar called glucose. Oxygen is released as a side product.
The Word Equation
Carbon dioxide + Water — (sunlight, chlorophyll) → Glucose + Oxygen
The Chemical Equation
Using chemical symbols, the same process is written as:
\[ 6\,CO_2 \;+\; 6\,H_2O \;\;\xrightarrow[\text{chlorophyll}]{\text{sunlight}}\;\; C_6H_{12}O_6 \;+\; 6\,O_2 \]Here \(C_6H_{12}O_6\) is glucose — the plant's immediate food, which it may later store as starch.
The Four Raw Materials
| Raw material | Where it comes from | How it enters the leaf |
|---|---|---|
| Carbon dioxide | Surrounding air | Through tiny pores called stomata |
| Water | Soil | Absorbed by roots, carried up to leaves by xylem |
| Sunlight | The Sun | Trapped by the green pigment chlorophyll |
| Chlorophyll | Inside leaf cells | Present in cell organelles called chloroplasts |
10.3 Chlorophyll — The Green Trap for Sunlight
Chlorophyll is a green pigment packed inside oval bodies called chloroplasts. Chloroplasts are most abundant in the leaves, which is why leaves look green. Chlorophyll acts like a tiny solar panel: it catches sunlight and converts that light energy into chemical energy stored in glucose.
10.4 Stomata — Doors for Gases
If you look at the underside of a leaf under a microscope, you will see thousands of tiny mouth-like openings. These are called stomata (singular: stoma). Each stoma is bordered by two bean-shaped guard cells that can swell up to open the pore or shrink to close it.
Through stomata:
- Carbon dioxide from the air enters the leaf for photosynthesis.
- Oxygen produced during photosynthesis escapes into the air.
- Extra water vapour is released — this is called transpiration (more in Part 3).
10.5 Where Does the Glucose Go?
The glucose made in leaves has two fates:
- Used immediately for the plant's own energy needs — growth, flowering, fruit-making.
- Stored as starch in leaves, stems, roots, fruits and seeds. Starch is insoluble, so it stays put without upsetting the cell's water balance.
That is why a potato, a grain of rice and a chapati all taste bland but release energy when digested — they are packed with starch originally built by photosynthesis.
Activity 10.1 — Testing a Leaf for Starch (Iodine Test) L3 Apply
You need: a potted plant (money plant or hibiscus), black paper, aluminium foil, a beaker, water, alcohol (spirit), iodine solution, a burner and forceps.
- Keep the plant in a dark cupboard for 48 hours so its leaves become starch-free (de-starching).
- Cover one half of a leaf with black paper on both sides; leave the other half exposed. Place the plant in sunlight for 4–6 hours.
- Pluck the leaf, remove the paper and boil it in water for 2 minutes to soften.
- Transfer the leaf to a small beaker of alcohol and warm it in a water-bath until the green colour fades.
- Rinse the pale leaf in warm water and spread it on a white tile. Pour a few drops of dilute iodine over it.
Predict: Which half of the leaf will turn blue-black when iodine is added — the covered half or the sunlit half? Why?
The sunlit half turns blue-black; the covered half stays pale yellow-brown. The blue-black colour is the chemical test for starch — it forms wherever iodine meets starch. Because the covered half received no sunlight, it could not carry out photosynthesis and so did not make starch. This proves that sunlight is essential for photosynthesis.
Important: Stomata are mostly found on the lower surface of a leaf. This reduces water loss because the lower surface is shaded and cooler than the upper side that faces direct sunlight.
10.6 Why Is Photosynthesis Important?
- It is the only major way food energy enters the living world. Every animal — from a grasshopper to a whale — ultimately depends on the glucose that plants make.
- It adds oxygen to the air. Without green plants, there would be no oxygen for us to breathe.
- It removes carbon dioxide from the air, keeping the atmosphere balanced and helping control Earth's temperature.
Competency-Based Questions
Meera's class sets up two identical potted plants. Plant A is kept in a bright sunny window; Plant B is moved into a dark cupboard. After three days, the teacher tests a leaf from each plant with iodine solution to check for starch.
1. Which gas is taken in by a leaf during photosynthesis? L1
(c) Carbon dioxide — it enters through the stomata and becomes part of the glucose molecule.
2. Why do leaves look green to our eyes? L2
Leaves contain a pigment called chlorophyll inside chloroplasts. Chlorophyll absorbs most of the red and blue wavelengths of sunlight but reflects the green wavelengths back to our eyes, so leaves appear green.
3. Fill in the blank: The tiny pores on the underside of a leaf through which gases move are called __________. L1
stomata (a single one is called a stoma).
4. In Meera's experiment, which plant's leaf will turn blue-black with iodine, A or B? Give a reason. L3
Plant A (the sunlit one) will turn blue-black because it carried out photosynthesis and stored starch in its leaf. Plant B stayed in darkness, so no photosynthesis occurred and little or no starch was made — iodine stays brown on that leaf.
5. True or False: Animals can carry out photosynthesis to make their own food. L1
False. Animals lack chlorophyll, so they cannot trap sunlight. They must eat plants or other animals to obtain food.
Assertion–Reason Questions
Choose: (A) Both true, R explains A. (B) Both true, R does not explain A. (C) A true, R false. (D) A false, R true.
A: Green leaves are often called the food factories of a plant.
R: Leaves contain chlorophyll, which captures sunlight energy for photosynthesis.
(A) — both statements are correct and R explains A. The chlorophyll in leaves is what makes photosynthesis possible.
A: A potato kept in a dark kitchen rack continues to contain starch.
R: The starch was stored earlier while the potato plant was carrying out photosynthesis in sunlight.
(A) — the starch is a stored food built earlier in sunlight, so it remains even when the potato is later placed in the dark.
A: Plants release oxygen during photosynthesis.
R: Oxygen is one of the raw materials needed to make glucose.
(C) — A is true; oxygen is given out. R is false; oxygen is a product, not a raw material. The raw materials are CO\u2082 and water.
Frequently Asked Questions — Photosynthesis — How Plants Make Food
What does the topic 'Photosynthesis — How Plants Make Food' cover in Class 7 Science?
The topic 'Photosynthesis — How Plants Make Food' is part of NCERT Class 7 Science Chapter 10 — Life Processes in Plants. It covers the key ideas of photosynthesis, chlorophyll, sunlight, carbon dioxide, water, glucose, oxygen, leaves, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Photosynthesis — How Plants Make Food' important for Class 7 NCERT Science?
'Photosynthesis — How Plants Make Food' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 10 — Life Processes in Plants — introduces photosynthesis and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Photosynthesis — How Plants Make Food?
The key concepts in 'Photosynthesis — How Plants Make Food' for Class 7 Science are: photosynthesis, chlorophyll, sunlight, carbon dioxide, water, glucose, oxygen, leaves. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 10 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Photosynthesis — How Plants Make Food taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Photosynthesis — How Plants Make Food' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 10 — Life Processes in Plants — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of photosynthesis can Class 7 students observe at home?
Class 7 students can observe photosynthesis at home in many simple ways linked to 'Photosynthesis — How Plants Make Food'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 10 — Life Processes in Plants. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Photosynthesis — How Plants Make Food' connect to other chapters of Class 7 Science?
'Photosynthesis — How Plants Make Food' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of photosynthesis appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 10 — Life Processes in Plants — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
AI Tutor
Science Class 7 — Curiosity
Ready