Photosynthesis

1
Photosynthesis

• An Overview

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Photosynthesis

• The general formula
• 6H2O 6CO2 ----------gt C6H12O6 6O2

3
What is the point of photosynthesis?

• 6H2O 6CO2 ----------gt C6H12O6 6O2

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What is the point of photosynthesis?

• To make sugar for the plant.

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• What three types of atoms are needed to make (be
  incorporated into) sugar?
• Where are they going to come from?

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What raw materials are needed to make (be
incorporated into) sugar?

• C, H, and O
• CO2 from the atmosphere (stomata)
• H2 derived from water from the soil (roots)

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Where in the leaf does photosynthesis take place?
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Where in the leaf does photosynthesis take place?
Chloroplast of leaf.
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How is the sugar produced?
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How is this sugar produced?

• The Calvin Cycle produces sugar in the
  chloroplast of the leaf.
• CO2 enters leaf through the stomata (regulated by
  guard cells)

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What is needed other than CO2 to produce glucose?
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What is needed other than CO2 to produce glucose?

• H2
• Energy

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Photosynthesis

• The production of sugar in the Calvin cycle does
  not require light ?it is often referred to as the
  dark or light-independent reaction.

H2
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Where does the plant get the H2 to add to the CO2
to make the glucose?

• 6H2O 6CO2 ----------gt C6H12O6 6O2

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Where does the plant get the H2 to add to the CO2
to make the glucose?

• H2 comes from splitting the H2O

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How does the water split?
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How does the water split?
LIGHT

• Light energy splits it.
• H2 used in the Calvin cycle
• O2 produced and given off as waste (gratefully
  accepted by animals for cellular respiration!)

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Where does the energy that powers the Calvin
cycle originate?
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Where does the energy that powers the Calvin
cycle originate?

• The energy also comes from light.

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What is the energy currency used most commonly by
cells?
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What is the energy currency used most commonly by
cells?

• ATP

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How do organisms make ATP?

• (Hint think about how we made it in cellular
  respiration)

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How do organisms make ATP?

• Electron transport chain. (ETC)

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How does the ETC work in photosynthesis?

• (Hint what powers the production of ATP?)

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How does the ETC work in photosynthesis?

• Light energy is absorbed by the chloroplast.
• An electron in the chlorophyll molecule gets
  excited and is boosted to a higher energy level.
• What goes up must come down and as it does it
  releases energy to make ATP.

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Photosynthesis

• Because this stage requires light energy to split
  the water and make ATP, it is often referred to
  as the light or light-dependent stage of
  photosynthesis.

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Photosynthesis
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How is light absorbed?

• What specific molecule is responsible for this?

This is the chloroplast - where this process
takes place.
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How is light absorbed?

• The chlorophyll molecule is specially designed to
  absorb certain wavelengths of light.

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Photosynthesis

• Which wavelength is the shortest?
• Which wavelength is the longest?
• Which wavelength has the most energy?
• Which wavelength has the least energy?

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Photosynthesis

• Which wavelength is the shortest?
• violet
• Which wavelength is the longest?
• red
• Which wavelength has the most energy? violet
• Which wavelength has the least energy? red
• What is the relationship
• between wavelength
• and amount of energy?

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Photosynthesis

• Pigments absorb light at various wavelengths.
• Absorption vs reflection
• Green light is reflected (into our eyes)
• The other colors are absorbed (used in photosyn.)
• Why do plants appear green?
• Plants appear green because most of the pigments
  in plants are chlorophylls the other pigments
  are hidden (except in the Fall).

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Why do plants have pigments other than
chlorophyll?
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Why do plants have pigments other than
chlorophyll?

• To absorb the wavelengths chlorophyll would miss!

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• How is the process of photosynthesis related to
  the process of cellular respiration?

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• How is the process of photosynthesis related to
  the process of cellular respiration?

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Photosynthesis
Use the following to Fill in the
blanks ATP CO2 H2O H2 O2 Calvin cycle
Light
Glucose
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Photosynthesis
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