Photosynthesis In Higher Plants In One Shot - JEE/NEET/Class 11th Boards | Victory Batch

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Photosynthesis in higher plants is a crucial process where plants create food using light, carbon dioxide, water, and chlorophyll. Different experiments and research have shown the importance of factors like light, chlorophyll, and water in the process of photosynthesis.

Insights

  • Photosynthesis is the process by which plants create food using light, carbon dioxide, water, minerals, and chlorophyll, producing glucose and oxygen through an anabolic and endothermic process.
  • Various experiments by scientists like Joseph Priestley, Jan Ingenhousz, and T.W. Engelmann have demonstrated the importance of air, sunlight, and specific light regions in photosynthesis efficiency.
  • The process of photosynthesis involves intricate mechanisms within chloroplasts, including photosystems, light harvesting complexes, electron flow, and the Calvin cycle, all crucial for glucose production in plants.

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Recent questions

  • What is photosynthesis?

    The process by which plants create food using light.

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Summary

00:00

"Essential Photosynthesis Process in Plant Physiology"

  • Photosynthesis in higher plants is a crucial chapter in plant physiology, with 2-3 questions typically asked yearly.
  • Photosynthesis is the process by which plants create their food using light, carbon dioxide, water, minerals, and chlorophyll.
  • The equation for photosynthesis involves 6 moles of CO2 and 12 molecules of water producing glucose and oxygen in the presence of light and chlorophyll.
  • Photosynthesis is an anabolic and endothermic process, requiring energy to produce glucose.
  • Plants are vital for purifying the air by releasing oxygen and converting light energy into chemical form for food production.
  • Joseph Priestley's bell jar experiment demonstrated the importance of air and oxygen in plant growth during photosynthesis.
  • Jan Ingenhousz's thistle funnel experiment highlighted the necessity of sunlight for photosynthesis by observing air bubbles in the presence of light.
  • Van Neil compared photosynthesis in green plants and purple/green sulfur bacteria, showing that the nature of the reducing agent determines the gas produced.
  • Rubin and Kamen experimentally confirmed that water, not CO2, is the source of oxygen in photosynthesis by doping oxygen with isotopes.
  • T.W. Engelmann proposed the first action spectrum, showing that photosynthesis is most efficient in the red and blue regions of the spectrum.

23:05

"Optimal Light for Photosynthesis: Engelmann's Experiment"

  • Tw Engelmann's experiment aimed to determine which region of white light is most effective for photosynthesis.
  • White light consists of seven components: vib gior (violet, indigo, blue, green, etc.).
  • Engelmann used a prism to split white light into its seven components.
  • Green algae was grown in front of each component of white light to observe photosynthesis.
  • Oxygen evolution rate was used to determine photosynthesis efficiency.
  • Aerobic bacteria flourished in red and blue regions, indicating maximum photosynthesis.
  • Green region showed poor oxygen evolution, indicating minimal photosynthesis.
  • Action spectrum graph plotted by Engelmann showed maximum photosynthesis in blue and red regions.
  • Photosynthesis in plants occurs in leaf mesophyll cells containing chloroplasts.
  • Chloroplast structure includes thylakoids for light reaction and stroma for dark reaction.

45:56

Photosynthesis: Light Absorption and Oxygen Evolution

  • Action spectrum graph shows rate of oxygen evolution with peaks in blue and red regions
  • Absorption spectrum indicates preferred ranges for photosynthetic pigments like chlorophyll a and b
  • Chlorophyll a absorbs in blue and red regions, while chlorophyll b mainly absorbs in the blue region
  • Accessory pigments like carotenoids and xanthophylls prefer the blue region only
  • Both action and absorption spectra show peaks in blue and red regions, indicating maximum photosynthesis
  • Photosystems consist of chlorophyll a, accessory pigments, and a reaction center on the thylakoid membrane
  • Photosystems are named PS1 and PS2 based on the discovery order, with PS2 functioning first
  • Light harvesting complexes (LHC) consist of accessory pigments bound to proteins, enhancing photosynthesis efficiency
  • Non-cyclic photophosphorylation involves electron flow between PS1 and PS2 on the thylakoid membrane to produce ATP and NADPH
  • PS2 absorbs light up to 680 nanometers (P680), while PS1 absorbs light beyond 680 nanometers (P700)

01:08:17

Electron Transport Chain in Photosynthesis: Key Steps

  • During the process of electron transportation, PS1 traps light of up to 700 nanometers, causing its electrons to become unstable and leave their valence shell.
  • The lost electron from PS1 is accepted by its primary electron acceptor, iron sulfur, leading to a transfer of electrons.
  • Plastocyanin, with an extra electron, passes it to PS1, fulfilling its electron requirement.
  • Electron flow occurs from PS2 to PS1 through various electron and proton acceptors on the membrane.
  • The electron from PS1 is passed to another electron acceptor, ferredoxin, which is then accepted by the enzyme NADP reductase.
  • NADP reductase accepts the electron and a free proton from the stroma, reducing NADP+ to NADPH2, a key end product of the light reaction.
  • Non-cyclic electron flow involves the transfer of electrons from PS2 to PS1, leading to the production of ATP and NADPH2.
  • Water splitting occurs to overcome PS2's electron deficiency, releasing protons, electrons, and oxygen gas as by-products.
  • ATP synthesis in non-cyclic photophosphorylation requires a living membrane, proton pumps, a proton gradient, and the enzyme ATP synthase located on the thylakoidal membrane.
  • Proton gradient is established through water splitting, plastoquinone activity, and NADP reductase, leading to ATP synthesis via ATP synthase.

01:29:45

"C3 Cycle: RuBP, Rubisco, Glucose Production"

  • The primary acceptor of CO2 in the stroma for converting it into glucose is a five-carbon compound called RuBP (ribulose bisphosphate).
  • RuBP combines with one carbon dioxide molecule to produce the first stable product, a three-carbon compound known as phosphoglyceric acid.
  • The cycle is referred to as the C3 cycle because the first stable product is a three-carbon compound, phosphoglyceric acid.
  • The enzyme responsible for this process is Rubisco (ribulose bisphosphate carboxylase oxygenase), which can bind with both CO2 and O2.
  • Rubisco's preference for binding with CO2 or O2 depends on their concentrations in the stroma.
  • If O2 binds with Rubisco instead of CO2, it leads to a wasteful process called photorespiration, reducing biomass production.
  • The C3 cycle involves three main steps: carboxylation, reduction, and regeneration of RuBP.
  • In the reduction step, phosphoglyceraldehyde is reduced to two molecules of three-carbon compound, phosphoglyceraldehyde, using NADPH2 obtained during the light reaction.
  • Regeneration of RuBP is crucial to maintain the cycle's continuity, requiring 1 ATP per RuBP regenerated.
  • For every glucose molecule produced through the C3 cycle, 18 ATP and 12 NADPH2 molecules are consumed.

01:52:05

"C4 Plants: Efficient Glucose Production and Adaptation"

  • The C3 cycle produces glucose by binding with the enzyme rubisco in the presence of rubp.
  • C4 plants also utilize the C3 cycle for glucose production as part of their overall C4 cycle.
  • C4 plants have additional mechanisms to increase CO2 concentration in bundle sheet cells, preventing photorespiration.
  • Examples of C4 plants include maize, sorghum, and sugar cane.
  • Plants adapted to dry tropical regions exhibit a C4 pathway for glucose formation alongside the Calvin cycle.
  • C4 plants possess unique leaf anatomy enabling them to tolerate high temperatures and intense light without photorespiration.
  • C4 plants feature Kranz anatomy with bundle sheet cells and mesophyll cells arranged around the vascular bundle.
  • The arrangement and cycle of C4 plants were studied by scientists Hatch and Slack, known as the Hatch and Slack pathway.
  • Photorespiration occurs when rubisco binds with O2 instead of CO2, leading to the production of phosphoglycolate and reduced phosphoglyceric acid.
  • Factors affecting photosynthesis include internal factors like leaf number, chlorophyll amount, leaf age, and product accumulation, as well as external factors like CO2, light, temperature, and water availability.
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