CH 8- PHOTOSYNTHESIS

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CH 8- PHOTOSYNTHESIS
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The Basics...
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8-1 Energy Life

• All living things require energy
• But what is it and where does it come from?

ATP
The Sun
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Autotrophs
make their own food
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Heterotrophs
have to eat!
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Chemical Energy ATP

• Cells use adenosine triphosphate to store
  release energy

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ATP!

• Is like a fully charged battery
• A phosphate can be or - to store or release
  energy

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How do we use ATP?

• It provides energy to work the sodium (Na)
  potassium (K) pump
• It provides energy for movement
• It powers the production of proteins and other
  molecules
• It even helps fireflies glow!

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8-2 Photosynthesis An Overview

• Plants use energy from the sun to convert water
  and carbon dioxide into carbohydrates (sugars
  starches) and release oxygen as a waste product

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• When a tiny seed grows into a tall plant where
  does its mass come from???

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• In addition to water and carbon dioxide,
  photosynthesis requires light and chlorophyll, a
  molecule in chloroplasts.

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• Sunlight, which you perceive as white light, is
  actually a mixture of different wavelengths of
  light.
• Your eyes see the different wavelengths of the
  spectrum as colors.

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• Chlorophyll does not absorb light well in the
  green region of the spectrum.
• Green light is reflected by leaves, which is why
  plants look green.
• Some of the light absorbed is converted directly
  to electrons in chlorophyll, raising the energy
  for photosynthesis.

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Inside a chloroplast
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Light Dependant Reactions

• Reactions requiring light produce O2 and convert
  ADP and NADP into the energy carriers ATP
  NADPH.
• This reaction requires light.
• It occurs in the thylakoid of a chloroplast.

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• Pigments in photosystem II absorbs light.
• The absorbed light increases the energy of
  electrons.
• Water is broken up into H and O2.
• Oxygen is released into the air.
• NADP picks up high energy electrons and H ions
  to produce NADPH.
• The inside of the membrane fills with H, making
  the outside negative.
• The difference of charge provides energy to make
  ATP.

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The Calvin Cycle

• ATP and NADPH are used from the light dependant
  reactions to produce high-energy sugars.
• Melvin Calvin worked
• out the details for this
• light independent
• reaction.
• Occurs in stroma.

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• A. CO2 molecules combine with carbon molecules.
  The result is 12-3 carbon molecules.
• Carbon molecules are converted into higher energy
  forms.
• Where do you think this energy came from?
• Some Carbon molecules are removed used to
  produce sugars other compounds.

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Factors affecting photosynthesis

• Shortage of water can slow or stop the process.
• Temperature should be between 0c 35c since
  enzymes work best at those temperatures.
• Light intensity
• can speed up
• the process up
• until a certain
• point.