x. photosynthesis ____________________________________________ – process of capturing light energy...
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X. PHOTOSYNTHESIS• ____________________________________________ – Process of capturing light
energy and converting it to chemical energy– Equation: __________________________________
• Plants are ________________________________ – “self-feeders”; also known as producers. – Ultimate source of all organic compounds comes from autotrophs
– ______________________________________________ – use sunlight as energy source
– ChemoautotrophsChemoautotrophs – do not use sunlight as energy source, use other compounds such as ammonia and sulfur
Location of Photosynthesis- Any green part of the plant has chloroplasts (site of photosynthesis)
- Leaves contain the most chloroplasts - Green color comes from ______________________________________- Chloroplasts are found mainly in the region of the leaf known as __________________________________- CO2 enters leaf through openings known as
________________________________- H2O enters via roots and is transported via veins
Chloroplast Structureo ________________________________ – site
of Light Reaction – 1st step in photosynthesis
o __________ __________ – stacks of thylakoids
o __________________________ – site of Calvin Cycle – 2nd step in photosynthesis
XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS• Occurs in ______________________________ membranesmembranes
• Converts light energy to chemical energy
• Light energy o Visible light is a small portion of the electromagnetic spectrum. o Light ________________________ by chlorophyll and other photosynthetic pigments to power
reactions is __________ seen. Light not utilized by plant is reflected & seen by human eye.
o Absorption spectrumAbsorption spectrum – graph illustrating how different pigments absorb different wavelengths of light
o Action spectrumAction spectrum – graph illustrating rate of
photosynthesis vs. wavelengtho Light energy measured in ______________________________.
3 Photosynthetic pigments ***1) Chlorophyll a***1) Chlorophyll a – absorbs mainly blue-violet and red light
2) Chlorophyll b2) Chlorophyll b – absorbs mainly blue and orange light3) Cartenoids3) Cartenoids – other accessory pigments; expand spectrum of
light energy that can be used for photosynthesis
XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS
• A photon of light energy is absorbed by pigment molecule in Photosystem II.
• Energy is passes from one molecule to another until it reaches P680 pair of chlorophyll a molecules.
• Electron is excited to higher energy state – transferred to primary electron acceptor.
• Water is split to replace electron lost by P680. O2 is released and H+ ions remain.
XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS
• Excited electron moves from primary electron acceptor to Photosystem I via electron transport chain. As electron “falls”, energy is released. Used to synthesize ATP through chemiosmosis.
• Light energy is transferred via light-harvesting complexes to P700 in Photosystem I.
• Excited electron is captured by primary electron acceptor. P700’s electron is replaced by electron transport chain on Photosystem II.
• Electron from P700 moves through a short electron transport chain, reducing NADP+ to NADPH.
XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS
Noncyclic PhosphorylationNoncyclic Phosphorylation
Cyclic Electron FlowCyclic Electron Flow• Alternative pathway seen in
some bacteria, plants
• May be photoprotective in plants
• Only utilizes Photosystem I
• No NADPH production
• No O2 release
• Does generate ATP
• So…..what’s the point???– To generate excess ATP
without generating NADPH– Calvin Cycle uses more ATP
than it does NADPH
XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS
XII. CALVIN CYCLECALVIN CYCLE OF PHOTOSYNTHESIS
• Also known as ____________________________________________, Light-Independent Rxn
• Occurs in ______________________________ of chloroplasts• ““Synthesis”Synthesis” part of photosynthesis
– Utilizes ____________________, ____________________ generated in Light Reaction, and ______________________ to produce organic molecules
• Anabolic; endergonic• Requires enzyme ______________________________• Three basic steps
Carbon FixationReductionRegeneration of RuBP
XII. CALVIN CYCLE OF PHOTOSYNTHESISInputInput
3 CO3 CO22 , 9 ATP, 6 NADPH , 9 ATP, 6 NADPH
OutputOutput
1 G3P, 6 NADP+, 6 Pi, 9 ADP1 G3P, 6 NADP+, 6 Pi, 9 ADP
XIII. PLANT ADAPTATIONS
• Major problems facing terrestrial plants is ____________________________.
• At times, solutions to this problem conflict with other metabolic processes, especially photosynthesis.
• The __________________________ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative evaporative loss of waterloss of water.
• On hot, dry days plants __________ the stomata__________ the stomata to conserve water, but this causes problems for photosynthesis.