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BISC 104 Principles of Biology
PHOTOSYNTHESISLAB
PS – What is it?
• Photo (use of light) – Synthesis (to synthesize sugar, related biomolecules)
• Sunlight (Energy) is required because:6 H2O + 6 CO2 C6H12O6 + 6 O2
Low energy High energy
molecules molecules
Why is PS Important?
• It produces Oxygen for all organisms• It produces Food (carbohydrates) which
is the base of all food chains
• It produces the C “backbone” for all biological molecules
• It removes CO2 from the atmosphere, off setting the greenhouse effect
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Where does PS take place?
Leaves – cells with chloroplasts (with pigments)
PS in the plant:The Raw Materials
• Water enters through roots• CO2 enters through stomata in leaves
• Air spaces surround leaf cells
Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
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Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
2�
&2�
Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
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Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
Cross section of leaf(Microscope slide used by permission of Carolina
Biological Supply Co.)
Intercellular Air spaces Stomata
Two Basic Reactions in PS
Overall Reaction (abbreviated):Sunlight
CO2 + H2O �
Low energy
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Two Basic Reactions in PS
Overall Reaction (abbreviated):Sunlight
CO2 + H2O �ATP, NADPH �Glucose + O2
Low energy High energy High energyIntermediates
Light-dependent reaction
Sunlight
Pigments
Light-dependent reaction
Sunlight
Pigments
H2O + ADP + NADP
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Light-dependent reaction
Sunlight
Pigments
H2O + ADP + NADP �ATP + NADPH + ½ O2
High energyintermediates
Light-dependent reaction
Sunlight
Pigments
H2O + ADP + NADP �ATP + NADPH + ½ O2
High energyintermediates
Light-independent reaction(Calvin cycle)
The “synthesis” part of photosynthesis:
CO2 + NADPH + ATP � Glucose
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Challenge Questions
• 1. What are ways to measure photosynthesis taking place?
Challenge Questions
• 1. What are ways to measure photosynthesis taking place?
• 2. What factors affect the rate of photosynthesis?
Ways to measure photosynthesis
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Ways to measure photosynthesis
• Use of CO2 – done in BISC207 labs
Ways to measure photosynthesis
• Use of CO2 – done in BISC207 labs
• Production of Glucose
Ways to measure photosynthesis
• Use of CO2 – done in BISC207 labs
• Production of Glucose• Evolution of O2 – this is basis of
BISC104 experiment
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Ways to measure photosynthesis
• Use of CO2 – done in BISC207 labs
• Production of Glucose• Evolution of O2 – this is basis of
BISC104 experiment• Use of water
What affects rate of PS?
What affects rate of PS?
• Light intensity
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What affects rate of PS?
• Light intensity• Wavelengths of light (color)
What affects rate of PS?
• Light intensity• Wavelengths of light (color)• CO2 concentration
What affects rate of PS?
• Light intensity• Wavelengths of light (color)• CO2 concentration
• Type of leaf (plant) used
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What affects rate of PS?
• Light intensity• Wavelengths of light (color)• CO2 concentration
• Type of leaf (plant) used• Age of leaf
What affects rate of PS?
• Light intensity• Wavelengths of light (color)• CO2 concentration
• Type of leaf (plant) used• Age of leaf
• Temperature
What affects rate of PS?
• Light intensity• Wavelengths of light (color)• CO2 concentration
• Type of leaf (plant) used• Age of leaf
• Temperature• Available soil water
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Lab 4 - Photosynthesis
• Uses O2 evolution to measure rate of light reaction (dependent variable)
• At different light intensities- (independent variable)
Hypothesis
The rate of photosynthesis, as
measured by O2 evolution, will
increase at higher light intensity and
decrease at lower light intensity
Theory behind Methods
• Discs are cut from leaves• Leaf discs have air in them
• Air is pumped from air spaces in leaf, replaced with HCO3; discs sink
• As PS occurs, O2 is produced• Air spaces fill up – discs float
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Theory behind Methods
• Rate of PS = How quickly do they float?What percentage float?
• Control – do discs float in dark? (no PS)
Results & Conclusions
• Collect Data
• Do Results Support Hypothesis?
Bright (lamp)
Low (room)
None
% floating# floatingLight
Additional Questions
• Did this experiment include the light independent reaction?
• What was purpose of bicarbonate?
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