Download x. photosynthesis

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
– Chemoautotrophs – 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 Structure
o ________________ – site
of Light Reaction – 1st step
in photosynthesis
o __________ – stacks of
thylakoids
o _____________ – site of
Calvin Cycle – 2nd step in
photosynthesis
X. PHOTOSYNTHESIS OVERVIEW, cont
XI. LIGHT REACTION OF PHOTOSYNTHESIS
• Occurs in _______________ membranes
• 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 spectrum – graph illustrating how different pigments absorb
different wavelengths of light
o Action spectrum – graph illustrating rate of
photosynthesis vs. wavelength
o Light energy measured in _______________.
XI. LIGHT REACTION OF PHOTOSYNTHESIS
3 Photosynthetic pigments
***1) Chlorophyll a – absorbs mainly blue-violet and red light
2) Chlorophyll b – absorbs mainly blue and orange light
3) Cartenoids – other accessory pigments; expand spectrum of light
energy that can be used for photosynthesis
XI. LIGHT REACTION OF PHOTOSYNTHESIS
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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 REACTION OF PHOTOSYNTHESIS
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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.
Noncyclic Phosphorylation
XI. LIGHT REACTION OF PHOTOSYNTHESIS
XI. LIGHT REACTION OF PHOTOSYNTHESIS
Cyclic 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
XII. CALVIN CYCLE OF PHOTOSYNTHESIS
• Also known as ______________________, LightIndependent Rxn
• Occurs in _______________ of chloroplasts
• “Synthesis” part of photosynthesis
– Utilizes __________, __________ generated in Light
Reaction, and ___________ to produce organic molecules
• Anabolic; endergonic
• Requires enzyme _______________
• Three basic steps
 Carbon Fixation
 Reduction
 Regeneration of RuBP
XII. CALVIN CYCLE OF PHOTOSYNTHESIS
Input
3 CO2 , 9 ATP, 6 NADPH
Output
1 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
loss of water.
• On hot, dry days plants __________ the stomata to
conserve water, but this causes problems for
photosynthesis.
XIII. PLANT ADAPTATIONS
C4
CAM