PHOTOSYNTHESIS
BIOLOGY
RIVERDELL HIGH SCHOOL
SO FAR….
Themes that keep arising:
Structure/function:
- proteins, -enzymes, cell membrane fluidmosaic model, phospholipid chemistry and
polarity…
Maintaining balance and characteristics of life:
-protein shape and temp/acidity, enzyme
specificity and homeostasis, osmosis- water
regulation , transport…
Conservation: of mass, of energy
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MOST RECENTLY: Structure/function of cell
membrane and its role in transport in order to
maintain homeostasis.
Which required energy?
In pairs: Where do our cells get energy from?
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What is the energy carrying molecule?
Where is the energy held in its structure?
What do we need to do to get energy? What are
“we” called?
Where does our energy ultimately come from?
PLANTS- PHOTOSYNTHESIS
WHERE IS THE KITCHEN OF
THE PLANT?
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CHLOROPLASTS
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IN THIS UNIT WE ARE GOING TO LOOK
AT THE STRUCTURE/FUNCTION of
CHLOROPLASTS IN GENERATING
ENERGY AND EXAMINE HOW LIGHT IS
CONVERTED TO CHEMICAL ENERGY
MAIN QUESTIONS:
Photosynthesis
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A. What is photosynthesis?
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B. Where does it take place?
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C. When does it take place?
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D. What happens during photosynthesis?
LAW OF CONSERVATION OF
ENERGY: Carbon Cycle
DO NOW:
1. What does the Law of conservation of energy
state?
2. What three things do plants need to stay
alive? What do they make from the raw
materials?
3. What are the equations for photosynthesis
and respiration?
4. THINK: Do plant cells undergo cell
respiration?
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What colored light is MOST useful in
photosynthesis? Least?
What colored light is MOST
USEFUL? Which is LEAST?
MOST USEFUL….
RED and BLUE
LEAST USEFUL
GREEN!!!
HOW CAN THIS BE?????
III. Light and Photosynthesis
A. Nature of Light
1. light is electromagnetic radiation
a.travels in a vacuum at
186,000miles/sec
b. other examples include microwaves,
radio waves, X-rays, gamma rays
c. each type has a different wavelength
and frequency
Nature of Light
2. white light is made of different colors
Red Orange Yellow Green Blue Indigo Violet
------------------------------------------------------------------------------------Decreasing wavelength --------------------->
---------------Increasing frequency and energy----------->
3. light that hits an object can be absorbed,
transmitted or reflected
4. color of light reflected is color you see
a. all colors reflected - color is white
b. all colors absorbed - color is black
c. all but blue absorbed - color is blue
The Visible Spectrum
WHAT DOES LIGHT PROVIDE?
Light in photosynthesis
provides energy that will be stored
in the bonds of a carbon compound
Bottom Line:
Photosynthesis can be divided into 2
phases:
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LIGHT REACTIONS: (NEED LIGHT)
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Light is converted into chemical energy
H20 breaks to H2 + O (release O2)
H20 is USED
O2 are MADE and ENERGY (ATP) !!!!
CALVIN CYCLE (Dark Reactions):
 CO2, is USED (and energy used)
 C6H12O6 is MADE
PHOTOSYNTHESIS
 6CO2 + 6H20 ------- C6H12O6 + 6O2
DO AS WE GO QUESTIONS
1. What are the 2 phases of photosynthesis?
2. Where do they occur?
….to answer this, we need to look at the
choloroplasts in detail…
Structure of the Chloroplast
WHERE DO THE LIGHT
PHASE AND CALVIN CYCLE
TAKE PLACE?
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LIGHT: Thylakoid
CALVIN CYCLE: Stroma
The Chloroplast
The Chloroplast and Pigments
1. Structure
a. grana: stacks of
thylakoid membranes
PIGMENTS:
1) chlorophyll a: absorbs light in the
red range and some in the blue range
2) chlorophyll b: absorbs more in the
blue range and assists chlorophyll a
DO…as we go Questions
How does light transfer its energy?
a. Pigments in chloroplast absorb light
1) light excites electrons
Excited electrons transfer energy to high energy compounds
IV. Light Phase - Photosynthesis
A. Chloroplast and Pigments
3) accessory pigments (carotenoids)
-yellow, orange, brown pigments that
absorb in the green range and
sometimes the blue range and pass
energy to chlorophyll a
THINK: Where do autumn leaves get
their colors?
Light Absorption by Pigments in the Chloroplast
Light Waves Absorbed and Reflected by the Leaf
Light Phase of Photosynthesis
VI. Alternate Pathways
C. CAM Pathway
1. Carbon dioxide is fixed in a variety
of compounds
2. open stomata at night and close
them during the day to conserve
water
3. these plants grow slowly
4. examples are cactus and pineapple
Cross Section of a Leaf
Stomata
Open
Closed
Several Stomata
Showing Guard Cells
Light and Dark Phase Compared
VII. Rate of Photosynthesis
A. Depends on
1. light intensity - increases as light
intensity increases, then levels off
2. temperature – increases, reaches a
high point, then decreases as
temperature increases
3. carbon dioxide levels – increases as
CO2 levels increase, then levels off
Light Intensity and Rate of Photosynthesis
Temperature and Rate of Photosynthesis
Temperature and Rate of Photosynthesis
CO2 Concentration and Rate of Photosynthesis
Three Factors Affecting Rate of Photosynthesis
Light Intensity
CO2 Concentration Temperature