Photosynthesis

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Photosynthesis

• Chapter 8
• By Kathryn Johnson

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All livings things need Energy!

• Autotrophs (Producers) Plants, algae, and some
  bacteria use light energy from the sun to produce
  food.
• Heterotrophs (Consumers) Animals, fungi, and
  some bacteria get their energy from the food they
  eat.

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Photosynthesis

• Plants use energy of sunlight to convert water
  and carbon dioxide into oxygen and high-energy
  carbohydrates (sugars)

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History

• 1643 Helmont plants gain most of their mass
  from water, not soil
• 1771 Priestley plants release O2 that keeps
  candle burning
• 1779 Ingenhousz aquatic plants produce O2
  bubbles only in daylight
• 1845 Mayer proposes that plants convert light
  energy into chemical energy

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History continued

• 1941 Ruben and Kamen O2 released in
  photosynthesis came from H2O
• 1948 Calvin light-independent chemical path
  that carbon follows to form glucose
• 1992 Marcus electron transfer in the electron
  transport chain

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Hydroponics

• Plants only get nutrients from the soil
• Plants can be grown in water w/ fertilizers

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Photosynthesis occurs in the Chloroplast
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Parts of the Chloroplast

• Thylakoids saclike photosynthetic membranes
• Photosystems clusters of pigment and protein
  that absorb light energy in the Thylakoids
• Grana/Granum stacks of thylakoids
• Stroma space outside thylakoids

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Pigments in the Chloroplast absorb Light Energy
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Light Wavelengths Colors

• The full spectrum of light is ROYGBIV, each color
  has a different wavelength
• Some light wavelengths are absorbed
• We see the other reflected wavelengths
• Different photosynthetic pigments absorb/reflect
  different wavelength of light
• Light travels as both energy (wavelength) and
  particles (photons)

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Chlorophyll absorbs red-blue and reflects
green-yellow
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Chlorophyll found in Chloroplasts
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Carotenoids

• When cold temperatures destroy the chlorophyll,
  other light absorbing pigments become . yellow,
  red, and orange . The fall colors

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Biochemical Energy

• ATP short-term stores energy for cell use
• Sugars Long-term storage of energy, stores 90x
  the energy of an ATP

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ATP/ADP

• Adenosine triphosphate (ATP)
• three Phosphates

• Adenosine diphosphate (ADP)
• two phosphates

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ATP-ADP Cycle

• When one phosphate bond is broken off the ATP,
  energy is released (exergonic)
• ATP H2O(Hydrolysis) -gt ADP Pi Energy
• In respiration ADP is rebound to the phosphate
  (endergonic)
• ADP Pi Energy -gt ATP H2O

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ATP stores energy by adding a phosphate to ADP
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ATP Energy

• Cells use ATP to power active transport across
  cell membrane (Na/K pump)

• ATP also powers organelle movement within the
  cell along microtubules in the cytoskeleton

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NADP/NADPH

• Nicotinamide Adenine Dinucleotide Phosphate
• NADP absorbs 2 high-energy e- and a H from
  water molecules in the electron transport chain
• NADPH transports the high-energy e- to other
  parts of the cell

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Energy storage

• Carbohydrates (sugars and starches) can store gt
  90x the energy of ATP
• Autotrophs capture sunlight and store its energy
  as sugars (like glucose fructose)

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Photosynthesis (2 parts)

• Light-dependent reactions
• Day-time
• e- transport chain
• In thylakoid membranes (grana)
• Produce ATP and NADPH
• Release O2 from H2O

• Light-independent reactions
• Night-time
• Calvin cycle
• In the stroma
• Use ATP, NADPH, and CO2
• Creates Sugars

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Light-Dependent Reactions

• Photosystem II
• pigments (chorophyll) absorb light and create
  high-energy electrons, the thylakoid membrane
  provides electrons from water (2e-, 2H,1O), O2
  gas is released
• 2e-, 2H move via electron transport chain from
  stroma into inner thylakoid as NADPH

• Photosystem I
• pigments use light to reenergize the 2e- (NADP
  2e- H -gt NADPH)
• Difference in charge across the thylakoid
  membrane provides energy to make ATP to drive the
  ATP synthase protein to transport H across the
  membrane

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Calvin Cycle

• ATP and NADPH energy must be stored as sugars
  because they dont last more than a few minutes
• 6CO2 enter from atmosphere and combine with 6
  5C-molecules to make 12 3C-molecules which absorb
  energy from ATP and NADPH
• 2 3C-molcules are converted into 6C-sugars
• The remaining 10 3C-molecules are converted back
  into 6 5C-molecules to continue the cycle

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Factors Affecting Photosynthesis

• Water effects the rate
  (waxy coating reduces
  water loss)
• Temperature (0-35?C) enzyme
  function
• Intensity of light (seasons/weather) until plant
  reaches maximum rate
• Summer growing season and winter dormant time
  causes rings on trees

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Essential Question

• Describe the process of photosynthesis.
• What roles do ATP, NADPH, and sugar play in
  energy transport and storage
• How does chlorophyll change light to chemical
  energy (light-dependent photosynthesis)?
• How does the plant cell change that energy into
  sugar (Calvin Cycle)?

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