10/13/2015
Plants are energy producers
• Like animals, plants need energy to live
– But, don’t need to eat food to make that energy
How do plants make energy & food?
Photosynthesis
• Plants use the energy from the sun
– to make ATP energy
– to make carbohydrates
sun
ATP
Sugar
Photosynthesis
• Process used by photoautotrophs to convert
solar energy into carbohydrates (glucose)
– 2 stages
The Two Stages of Photosynthesis: A
Preview
• Photosynthesis consists of
– light-dependent reactions
• the photo part
– Light-independent reactions
• 6CO2 + 6H2O + Energy  C6H12O6 + 6O2
• Calvin cycle
• the synthesis part
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10/13/2015
Using light & air to grow plants
• Photosynthesis
– using sun’s energy (and water) to make ATP
– using CO2 & water to make sugar
– in chloroplasts
– allows plants to grow
– makes a waste product
• oxygen (O2)
What do plants need to grow?
• The “factory” for making
energy & sugars
– chloroplast
• Fuels
– sunlight
– carbon dioxide
– water
• The Helpers
sun
CO2
ATP
enzymes
H2O
– enzymes
H2O
CO2
sugars
The light-dependent reactions
Light
LIGHTDEPENDENT
REACTIONS
NADP+
ADP
LIGHTINDEPENDENT
REACTIONS
(CALVIN CYCLE)
ATP
NADPH
O2
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Energy storing reactions
Occur in the thylakoids
Split H2O
Release O2
Store electrons in NADPH
Generate ATP using sunlight
[CH2O] (sugar)
Light-Independent Reactions
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Carbohydrate builder
Occur in the stroma
Use CO2
Use ATP
Use H2O
Use electrons in NADPH
Generate carbohydrate (CH2O)
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10/13/2015
Photosynthesis
Chloroplasts and Pigments
sun
H2O
O2
ENERGY
building
reactions
used immediately
to synthesize sugars
ATP
ADP
• Chloroplasts use pigments to trap sunlight
– Pigments give plants color
– Chlorophyll is most common pigment
• Plants are green because chlorophyll reflects green
light
SUGAR
building
reactions
H2O
sugar
CO2
Factors that Effect Rates of
Photosynthesis
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Leaf Structure
Light Intensity
Carbon dioxide levels
Temperature
pH
• **Any factor that influences enzymes will
influence photosynthesis
Function of Leaf Structures
• Cuticle
– waxy coating reduces water loss
• Epidermis
– skin protecting leaf tissues
• Palisade layer
– High chloroplasts
– Photosynthesis
• Spongy layer
– air spaces
Stomata & Guard Cells
• Function of stomata
– CO2 in
– O2 out
– H2O out
• gets to leaves for
photosynthesis
• Function of guard cells
– open & close stomata
• gas exchange
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10/13/2015
Energy cycle
sun
Photosynthesis
plants
CO2
glucose
H2O
sugars
O2
animals, plants
Cellular Respiration
ATP
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