Photosynthesis

• Water movement from the soil through the plant into the atmosphere

  1. Water potential

  2. Root pressure

  3. Adhesion force

  4. Cohesion force

  5. Transpiration force
• Water potential


  Water moves from high water potential to low water
• Root pressure


  • Is an upward force
  • Responsible for guttation
• Adhesion force


  • Forces that attach water molecules TO xylem
• Cohesion force


  • Forces that keeps water molecules together
• Transpiration force


  • Pulls the columns of water to the atmosphere
• All these forces are important in the absorption and translocation
• Metabolism - totality of an organism's chemical reactions
• Metabolism are very important for survival and functioning of the organism
• Metabolism are all regulated to balance metabolic supply and demand
• Catabolism/catabolic process


  Breakdown of complex molecules
• Anabolism/anabolic process


  Synthesis of complex molecules
• Modes of acquiring organic compounds

  • Photosynthesis
  • Heterotrophy
• Photosynthesis


  Process of converting light energy from the sun to chemical energy stored in sugar and other organic molecules
• Light bands


  Blue and red are two wavelengths absorbed by chlorophyll
• Photosynthesis process


  1. Photosynthesis is a two stage process

  2. The first process is the Light Dependent Process (Light Reactions)

  3. Occurs on thylakoid membranes

  4. Convert solar energy to chemical energy

  5. The second process is the Light Independent Process (Dark Reactions)

  6. Melvin Calvin

  7. Takes place in the stroma

  8. Controlled by enzymes
• Photosynthesis process


  • Light Dependent Process
  • Light Independent Process
• Light Dependent Process


  1. Linear electron flow

  2. ETC 1

  3. a.plastoquinone

  4. Cytochrome complex

  5. plastocyanin

  6. ETC 2

  7. ferredox

  8. Cyclic electron flow

  9. Uses only photosystem I

  10. No production of NADPH

  11. No oxygen is released

  12. Produce ATP

  13. Plant well adapted to grow well under intense light (C4 plants)

  14. Photoprotection
• Calvin cycle


  1. Carbon fixation

  2. CO2 molecule incorporated to 5 carbon sugar (ribulose bisphophate -RuBP)

  3. Process catalysed by RuBP carboxylase

  4. Most abundant enzyme on earth

  5. 6-C product very unstable and breaks into two molecules- 3-phosphoglycerate

  6. Reduction

  7. 3-phosphoglycerate receives phosphate from ATP to become 1,3 biphosphogylcerate

  8. Losses a phosphate group and its reduced by NADPH to gylceraldehyde 3-phosphate (G3P)

  9. One molecule of G3P exit the cycle

  10. Regeneration of the CO2 acceptor RuBP

  11. 5 molecules of G3P are arranged into three molecules of RuBP

  12. 3 molecules of ATP are spent
• To produce one molecule of G3P 9 molecules of ATP and 6 NADPH are used
• G3P used to synthesis other organic compounds including glucose
• Different Plants in Terms of Photosynthesis

  • C3 plants
  • C4 plants
• C4 pathway


  1. PEP = phosphoenolpyruvate

  2. Enzyme PEP carboxylase has higher affinity for CO2 and no affinity for O2

  3. CO2 concentration pump that keeps CO2 concentrations high for RUBP carboxylase

  4. Minimises photorespiration

  5. Advantageous in hot regions with intense sunlight

  6. Eg. Sunflower and maize
• CAM plants
• Sepals


  Leaves that protect the flower before it opens
• Petals


  Colourful leaf-like structure that attract animals and insects
• Calyx


  When all the sepals of the petals are fused together
• Perfect flower


  Flower that has both male and female parts
• Imperfect flower


  Flower that is missing either male or female parts
• Flower parts


  • Sepals
  • Petals
  • Pistils
  • Stamens
• Complete flower


  Flower that has sepals, petals, pistils and stamens
• Incomplete flower


  Flower that is missing sepals, petals, pistils or stamens
• Angiosperms are plants that produce flowers and bear their seeds in fruits
• Gametophyte


  A haploid multicellular plant form that has only a single set of chromosomes
• Stamen


  The male part of the flower
• Anther


  Sac-like structure that contains pollen
• Filament


  Stalk-like part of the stamen that holds the anther
• Pistil


  The female part of the flower
• Stigma


  Sticky part of the pistil that is receptive to pollen
• Style


  Part of the pistil between the stigma and ovary