Photosynthesis

• Photosynthesis

  • The process that feeds the Biosphere
  • A process that converts solar energy to Chemical Energy
• Plants and other Autotrophs

  • Producers of the Biospher
• Plants use energy of the sunlight to make organic molecules from water and CO2
• Photosynthesis occurs in plants and algae
• Heterotrophs obtain their organic material from other organisms
• Leaf is the major site of photosynthesis
• Chloroplast

  • organelles where photosynthesis occurs
  • it contains Thylakoids
• Photosynthesis formula: 6CO2 + 12H2O + light energy = C6H12O6 + 6O2
• Chloroplast splits water into: Hydrogen and Oxygen incorporating the electrons of H into sugar molecules
• Photosynthesis is what kind of reaction?

  A redox reaction
• What are the 2 processes of Photosynthesis?

  • light reaction
  • Calvin Cycle
• Light reaction

  • occurs in the Grana
  • splits water, releases Oxygen
  • produces ATP and forms NADPH
• Calvin cycle

  • occurs in the stroma
  • forms sugar from CO2, using ATP for energy and NADPH for reducing power
  • similar to the Citric Acid Cycle
• Light is a form of electromagnetic energy which travels in waves
• Wavelength is the distance between the crest of waves and determines the type of electromagnetic energy
• Pigments are substances that absorb visible light
• Spectrophotometer: Machine that sends light through pigments and measures the fraction of light transmitted at each wavelength
• Chlorophyl A: main pigment

  Chlorophyl B: accessory pigment
• When a pigment absorbs light

  • it goes from a ground state to an exited state which is unstable
• Particles of light are Photons
• Photosystem

  • light harvesting center
  • found in the thylakoid membrane
• Light harvesting complex

  • made of pigment molecules bound to particular proteins
  • funnel the energy of photons of light to the reaction center
• Thylakoid Membrane is populated by two types of Photosystem I and II
• Noncyclic electron flow

  • the primary pathway of energy transformation in the light reactions
  • Produces NADPH, ATP, and Oxygen
• PS II (photosystem) steps:

  *P680 chlorophyl

  1. light charges chlorophyll
  2. water splits and males O2 and gives e- to trampoline
  3. e- bounces to primary acceptor
  4. e- from primary acceptor goes under ETC and makes ATP
  5. e- goes to PS I
• PS I Steps:

  *P700 chlorophyll

  1. light charges chlorophyll
  2. e- bounces to primary acceptor
  3. e- goes to another ETC
  4. makes NADPH
• In Cyclic Electron Flow

  • only PS I is used
  • Only ATP is produced
• Chloroplasts and mitochondria

  • Generate ATP by the same basic mechanism: chemiosmosis
  • But use different sources of energy to accomplish this
• The Calvin cycle uses ATP and NADPH to convert CO2 to sugar
• The Calvin cycle

  • Is similar to the citric acid cycle
  • Occurs in the stroma
• The Calvin cycle has three phases:

  • Carbon fixation
  • Reduction
  • Regeneration of the CO2 acceptor
• Rubisco:

  • Ribulose Biphosphate Carboxylase Oxygenase
  • lets Carbon enter the Calvin Cylce
• Lenticel

  • opening in the stem of the plant
  • same functions as stomata
• Photorespiration

  • O2 substitutes for CO2 in the active site of the enzyme Rubisco
• On hot, dry days, plants close their stomata

  • Conserving water but limiting access to CO2
  • Causing oxygen to build up
• C4 plants minimize the cost of photorespiration

  • By incorporating CO2 into four carbon compounds in mesophyll cells
• CAM plants

  • Open their stomata at night, incorporating CO2 into organic acids
  • And the CO2 is released from the organic acids for use in the Calvin cycle
• Organic compounds produced by photosynthesis

  • Provide the energy and building material for ecosystems