Class 11 Biology - KERALA
Photosynthesis in Higher Plants
The chapter Photosynthesis in Higher Plants explores how green plants manufacture their own food using light energy, carbon dioxide, and water. Students will study the anatomical and biochemical sites of photosynthesis, the role of photosynthetic pigments, and the two main phases: light-dependent reactions and dark reactions (Calvin cycle). It also covers alternative pathways like C4 and CAM pathways, alongside photorespiration. This chapter is exceptionally high-yielding in Kerala SCERT Class 11 biology board exams, frequently featuring diagram-based questions from the Z-scheme, Calvin cycle, and comparisons between C3 and C4 plants.
Start Learning FreeKey Concepts
Site of Photosynthesis
Photosynthesis primarily takes place in the chloroplasts, specifically within the thylakoids (site of light reactions) and the stroma (site of dark reactions).
Pigment Systems (Photosystems)
Photosystem I (PSI) and Photosystem II (PSII) are complexes of proteins and photosynthetic pigments that absorb light energy and drive electron transport.
Light Reaction (Photophosphorylation)
A process occurring in thylakoid membranes where ATP and NADPH are synthesized using solar energy, involving photolysis of water and the Z-scheme of electron transport.
Calvin Cycle (C3 Pathway)
The dark reaction occurring in the stroma where carbon dioxide is fixed into sugars in three stages: carboxylation, reduction, and regeneration of RuBP.
C4 and CAM Pathways
Specialized carbon fixation adaptations in tropical and arid plants that minimize photorespiration by using PEP carboxylase for initial CO2 capture.
Important Formulas
Board Exam Info
In Kerala SCERT Class 11 Biology examinations, this chapter typically carries around 6 to 8 marks. Questions frequently include distinguishing between C3 and C4 plants, explaining the Z-scheme of light reaction with a diagram, outlining the Calvin cycle, and describing factors affecting photosynthesis (Blackman's Law of Limiting Factors).
Frequently Asked Questions
C3 plants have a 3-carbon stable product (PGA) and undergo more photorespiration, while C4 plants have a 4-carbon compound (oxaloacetate) with Kranz anatomy, making them more efficient in high temperatures.
C3 plants form a 3-carbon PGA as the first CO2 fixation product and suffer from photorespiration. C4 plants form a 4-carbon OAA, possess Kranz anatomy, and efficiently fix carbon at higher temperatures without significant photorespiration.
Water splitting (photolysis) releases electrons to replace those lost by PSII, provides protons for NADPH formation, and releases oxygen as a byproduct.
Photolysis of water provides the electrons needed to replace those lost by Photosystem II, releases oxygen into the atmosphere, and generates protons required for ATP synthesis.
It states that if a chemical process is affected by more than one factor, its rate is limited by the factor that is nearest to its minimal value.
This law states that when a process is conditioned as to its length by a number of separate factors, the rate of the process is controlled by the pace of the slowest factor, i.e., the factor closest to its minimum value.
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