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PHOTOSYNTHESIS
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Different Types of Organisms as to
Mode of Nutrition:
1. Photoautotrophs
- organisms obtain their energy through
photosynthesis
ex. Plants, algae, photosynthetic bacteria2. Heterotrophs
- rely on other organisms for organic molecules to
build their bodies
3. Chemoautotrophs- obtain their carbon from CO2 and energy from
inorganic chemicals
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Differences between autotrophs and
heterotrophs
Source of energy
Source of building
materials
Organisms
Photoautotrophs Heterotrophs
Sunlight
carbon dioxide
photosynthetic plants
AlgaeCyanobacteria
Photosynthetic bacteria
Food:proteins
carbohydrates
Food
Completeley parasitic plants
FungiAnimals; protozoa
Non-photosynthetic parts of
plants
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Photosynthesis
Is the process by which green plants and
autotrophic organisms synthesize food.
6CO2 + 12H20 C6H12O6 + 6O2 + 6H2Ochl
light
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AN OVERVIEW OF PHOTOSYNTHESIS
• Photosynthesis is the process by which
autotrophic organisms use light energy to
form sugar and oxygen gas from carbon
dioxide and water
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Photosynthesis
- use light energy to
convert CO2 and H2O into
sugar
- chloroplast
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The location and structure of chloroplasts
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Chloroplast
- plastid
- organelle involved in
making or storing food and
pigments
- chlorophyll
- site of photosynthesis
- stem and leaves
-3-5um in diameter,spherical or elongated
- 2 membranes
- thylakoids
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Grana
- Conversion of solarenergy to chemical
energy takes place
within the
membrane of the
thylakoids
Stroma
- site of sugarproduction and storage
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2 Series of Reactions
I. Light Reaction
II. Dark Reaction/ Calvin Cycle
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An overview of photosynthesis
H20
Light Chloroplast
CO2
CALVIN
CYCLE
(in stroma)
LIGHT
REACTIONS
(in grana)
ATP
NADPH
NADP+
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I. Light Reactions
• Thylakoid membrane
• Photo part of
photosynthesis
•Capture light energy
• O2 (by product)
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II. Calvin Cycle
• Stroma
• Synthesis part of photo-
synthesis
• Assembles 3 simple
carbon sugars using ATP
and NADPH from light
reactions and CO2 fromthe air
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LIGHT REACTIONS
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The Nature of Light
• Wavelength is the
distance from peak to
peak
• Energy is inverselyproportional to the
wavelength
• Longer wavelength the
less energy
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Types of Chlorophyll
1. Chlorophyll a
- only pigment directlyinvolved in lightreactions
- absorbs light from blueviolet and red ranges of spectrum
- wavelength in red and
blue ranges of spectrumstrongly drivephotosynthesis
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Accessory pigments
1. Chlorophyll b c, d, e
- does not take part directly in light reactions
- transmit absorbed energy to chlorophyll a
molecules- accessory pigment
2. carotenoids
- absorb blue-green light and absorb yellow oryellow- orange lights
3. xanthophyll
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Light energy enters photosynthesis at locations
called photosystems ( light harvesting units)
Primary
electron acceptor
PHOTOSYSTEM
Reaction center
Pigment
molecules
of antenna
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Movement of electrons in the light reactions
- little chlorophyll b
- Almost same amount
of chlorophyll a and b
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II. CALVIN CYCLE
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Internal Anatomy of Leaf- Dicot
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CAM Photosynthesis
•
Crassulacean Acid Metabolism• Carbon dioxide is converted to an acid and stored during
the night
• Stomata open at night
•
During the day the acid is broken and carbon dioxide isreleased to Rubisco for photosynthesis
Adaptive Value:
- better water use efficiency (lower transpiration rates)
- thrive in conditions of high daytime temperatures• CAM plants include many succulents such as
cactuses, agaves, some orchids and bromeliads
pineapple
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