Class 10 Science - ICSE-BIOLOGY
Photosynthesis
The chapter 'Photosynthesis' in Class 10 ICSE Biology explores how green plants manufacture their own food using sunlight, water, and carbon dioxide. You will learn about the detailed mechanisms of the light-dependent and light-independent phases, the structure of chloroplasts, and the various factors affecting the rate of photosynthesis such as light intensity, $\text{CO}_2$ concentration, and temperature. This chapter is vital for board exams as it consistently features in structured essay-type questions, diagram-based labeling, and experimental setups testing the necessity of specific factors for photosynthesis, carrying roughly 8 to 12 marks in the final Biology paper.
Start Learning FreeKey Concepts
Photosynthesis
The process by which green plants prepare their own organic food (glucose) from carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen as a byproduct.
Light-dependent Phase (Photochemical Phase)
Occurs in the grana of chloroplasts where sunlight is trapped by chlorophyll to split water molecules (photolysis), releasing oxygen, ATP, and NADPH.
Light-independent Phase (Biosynthetic Phase)
Occurs in the stroma of chloroplasts where ATP and NADPH produced in the first phase are used to reduce carbon dioxide into glucose without requiring direct sunlight.
Chloroplast
The double-membrane bound cell organelle containing thylakoids (grana) and stroma, which serves as the actual site of photosynthesis in plant cells.
Adaptations in Leaves
Structural features of leaves like a broad lamina, large number of stomata, branching veins, and thin epidermis that maximize light absorption and gas exchange for photosynthesis.
Blackman's Law of Limiting Factors
States that when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest factor.
Important Formulas
Board Exam Info
In the ICSE Class 10 Biology paper, Photosynthesis typically carries around 8 to 12 marks. Common question types include diagram-based questions (labeling parts of a chloroplast or experimental setups), direct definitions, word equations, and reasoning questions based on experiments (such as destarching leaves or proving that carbon dioxide is necessary).
Frequently Asked Questions
Why is sodium bicarbonate added to water plant experiments?
Sodium bicarbonate is added to water to act as a readily available source of dissolved carbon dioxide for the aquatic plant during photosynthesis experiments.
Why do we need to destarch a potted plant before conducting an experiment?
Destarching ensures that the existing starch in the leaves is used up, so any starch found at the end of the experiment is newly synthesized solely during the test period.
Is oxygen produced in photosynthesis derived from water or carbon dioxide?
Oxygen released during photosynthesis is derived entirely from water molecules through a process called photolysis, as proven by isotope tracer studies.
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