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Photosynthesis

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Energy and Life

  • Nearly every activity in modern society depends on Energy…think about it.
    • Driving a car!
    • Typing a paper!
    • Using your IPhone!
  • Living things also require ENERGY!

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Where does that Energy come from?

  • Autotrophs (AKA: Producers)
    • Use the sunlight as their ENERGY source.

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Heterotrophs (AKA: Consumers)

    • Obtain energy from the plants or other organisms that they consume.

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Chemical Energy

  • Candles burn
    • What does that mean?
  • Wax molecules store energy in the bonds between the hydrogens and carbons

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  • Electrons move from higher energy levels to lower energy levels.
  • Heat and light energy are released.

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Living things use and store energy

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Plants store energy as sugar or starch

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Animals store energy as glycogen (animal starch)

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Or as fat

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ATP: Adenosine Triphosphate

  • Adenine
  • Ribose:5 carbon sugar
  • 3 phosphate groups

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Storing Energy

  • ADP (adenosine diphosphate) is a compound that looks like ATP except it is lacking a __________ group.

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  • This one difference is the key to the way in which living things store energy.

Phosphate

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Storing Energy (cont.)

  • When a cell has energy available, it can store small amounts of it by adding a phosphate group to ADP, producing ATP.

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  • Think of ATP as a fully charged battery and ADP as only a partially charged battery.
  • Now that we have Energy stored…how do we release it?....

http://www.biologyinmotion.com/atp/index.html

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Releasing Energy

  • Energy that is stored in ATP is released by breaking the chemical bond between the second and third phosphates.

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What the energy in ATP can do

  • Active transport
  • Protein synthesis
  • Muscle contraction

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What the energy in ATP can do

  • Synthesis of nucleic acids
  • Move organelles throughout the cell
  • Responds to chemical signals of cell
  • Fireflies!

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Question?????

  • Do you think cells have an abundant amount of ATP?
    • Answer: Most cells have only a small amount of ATP, enough to last them for a few seconds of activity.
  • Why?
    • Answer: ATP is great for transferring Energy, not for storing Energy.

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ATP Wrap-UP

  • Long term storage is done by other molecules, such as glucose, glycogen, starch
  • ATP can be regenerated by the cell over and over again
    • ADP + Energy + P → ATP
    • Required energy comes from food molecules

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8-2:Overview of Photosynthesis

  • Van Helmont’s Experiment
    • Plants gain mass from water
  • Priestley
    • Plants produce oxygen
  • Jan Ingenhousz
    • Light is necessary

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8-2:Overview of Photosynthesis

  • Photosynthesis converts light energy into the chemical energy of sugar and other organic compounds.
  • Light energy drives the reactions
  • O2- byproduct and is released into atmosphere

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The Photosynthetic Equation

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Light and Pigments

  • Pigments: light absorbing molecules
    • Chlorophyll absorbs blue-violet and red light
  • When a pigment absorbs light, it absorbs the energy from that light
    • Energy excites electrons

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8-3: The Reactions of Photosynthesis

  • Where does photosynthesis take place?

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Parts of the chloroplasts

  • Thylakoids-Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters known as photosystems.

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Parts of the chloroplasts

  • Photosystems-light collecting units
    • Reactions of photosystems in 2 parts:
      • Light-dependent reactions (take place in thylakoid membrane)
      • Light-independent reactions (take place in the stroma)

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Light-Dependent Reactions

  • The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into ATP and NADPH.

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  • Occur in the thylakoid

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Calvin Cycle (light-independent)

  • The Calvin Cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.

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  • It takes carbon dioxide from the atmosphere and converts it into high-energy sugars that can be used to meet the plant’s energy needs and to build more complex molecules.

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What does all of that mean?

  • The two sets of photosynthetic reactions work together…
    • The light-dependent reactions trap the energy of sunlight in chemical form
    • The light-independent (Calvin cycle) uses that chemical energy to produce stable, high-energy sugars from carbon dioxide and water.

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Factors Affecting Photosynthesis

  • Shortage of water can slow down or stop photosynthesis
    • Plants have adaptations to reduce water loss: waxy coating on plants in dry areas.
  • Temperature
    • Plants have enzymes that work best from 32-95 degrees F. Temperatures above or below can damage these enzymes which can slow down or stop photosynthesis.

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Factors Affecting Photosynthesis

  • Intensity of light
    • Increasing light intensity increases the rate of photosynthesis. (It will reach a max level)

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