Photosynthesis

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Photosynthesis
6H2O 6CO2 ----------gt C6H12O6 6O2
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Photosynthesis
"putting together with light."
What is photosynthesis? Photosynthesis is
arguably the most important biological process on
earth. By liberating oxygen and consuming carbon
dioxide, it has transformed the world into the
hospitable environment we know today.
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Importance of Photosynthesis

• If we can understand and control the intricacies
  of the photosynthetic process, we can learn how
  to increase crop yields of food, fiber, wood, and
  fuel, and how to better use our lands. The
  energy-harvesting secrets of plants can be
  adapted to man-made systems which provide new,
  efficient ways to collect and use solar energy.

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Photosynthesis takes place in three stages 1.
Energy is captured from sunlight 2. Light energy
is converted to chemical energy(ATP/NADPH) 3. ATP
and NADPH power the formation of glucose using
carbon from CO2
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Molecules in Photosynthesis
Chlorophyll a Chlorophyll b
Green pigments that absorb light energy
Carbon Dioxide - CO2, source of carbon for sugar
formation
Water - H2O, source of hydrogen for sugar
formation and important for moving energy during
photosynthesis
Oxygen - O2, by-product of photosynthesis
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Molecules in Photosynthesis, continued
ATP(ADPP) - Energy carrying molecule
NADPH(NADPH) - Energy carrying molecule
Electron Acceptors - proteins that move
electrons during photosynthesis
Proton Pump - protein that moves protons (H)
during photosynthesis
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Molecules in Photosynthesis, continued
Enzymes (e.g. ATP synthetase) - proteins that
speed up the chemical reactions
RBP - 5 carbon molecule used to build glucose
PGAL - 3 carbon molecule used to
build glucose
Glucose - C6H12O6, Food product of
photosynthesis
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Photosynthesis takes place in the chloroplast
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Inside the Cholorplast
Thylakoid - membrane sac holds the
chlorophyll molecules photosynthesis takes
place here Grana - column of thylakoids Stroma
- liquid that fills the chloroplast
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Energy is captured from sunlight
Light is a form of radiant energy - emitted in
waves that can travel through a vacuum
The complete range of radiant energy is called
the electromagnetic spectrum
Electromagnetic spectrum
Units nm nanometer (10-9 m or one-millionth of
a millimeter) Km kilometer (103 m or
one-thousand meters)
Radiant Energy travels in tiny packets called
photons
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Back it up
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Chlorophyll Absorbs Photons
There are 2 types of chlorophyll molecules in the
thylakoid membrane Chlorophyll a Chlorophyll
b They both produce a green color- but absorb
slightly different wavelengths of light energy
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Processing Based on
Absorption Spectra
What colors of light are best absorbed by the
chlorophyll molecules? Chlorophyll a - Indigo
and Orange Chlorophyll b - Indigo/Blue and
Orange/Red
What colors of light are least absorbed by the
chlorophyll molecules? Green and Yellow
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Back it up
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How does this data support the fact that the
chlorophyll molecules give plants their green
color?
Because green and yellow are NOT absorbed, they
are reflected to your eye giving chlorophyll the
green color.
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• Photosystems-are clusters of Chlorophyll
• molecules in the thylakoid membrane.
• There are two clusters called
• photosystem I and photosystem II
• These Photosystems start the process of
  photosynthesis by absorbing photon energy
• This energy is captured by electrons in the
  cholorphyll molecules.

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Light Energy is Converted into Chemical Energy
This stage of photosynthesis is also called the
Light Reactionbecause light energy is required.
1. Photons reach the chlorophyll molecules in the
photosystems found on the thylakoid membrane and
are absorbed by these molecules.
2. Electrons in the chlorophyll become
energized from these photons and are passed
from Photosystem II to Photosystem I.
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3. In the process of passing electrons -energy
is stored in ATP and NADPH molecules -H2O
molecules are split into O2 - released as a
by-product into the atmosphere H - used to
form NADPH
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Chemical Energy is Stored in Glucose
The other stage of photosynthesis is also called
the Dark Reaction or the Calvin Cycle
-no light energy is required -occurs in the
stroma of a chloroplast
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Molecules Important to the Calvin Cycle
ATP - releases energy to keep cycle going NADPH
- releases energy to keep cycle going
-provides the hydrogen for the glucose
molecule RuBP -5 carbon molecule used over and
over in the cycle to form glucose PGAL -
3 carbon molecule used over and over in cycle to
form glucose CO2 - carbon source for cycle
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What affects the rate of photosynthesis?
Light intensity - as light intensity increases
the initial rate will increase and eventually
level off as all of the electrons in the
photosystems are excited.
Carbon dioxide - increasing levels of CO2 will
increases the rate initially. So, talking to
your plants is a good thing. )
Temperature - increasing temperature increases
all chemical reactions, including those in
photosynthesis.