Photosynthesis

• Metabolism is a chemical process that occurs in a cell
• Anabolic reactions are a building up process where large, complex molecules are synthesized from simpler molecules
• Catabolic reactions are a breaking-down process of large molecules
• Oxidation-reduction reactions occur in metabolism, including in photosynthesis and cellular respiration
• Electron transport chain is a series of chemical reactions where hydrogens or their electrons are passed from one acceptor molecule to another, releasing energy
• Photosynthesis is a biological process that involves capturing light energy and transforming it into chemical energy of organic molecules
• Non-cyclic electron transport and photosystem involve chemiosmosis, which is the synthesis of ATP using a proton gradient established across a membrane
• Calvin cycle (step) of photosynthesis
• Phase 1: Carbon fixation (CO2 uptake)

  • Absorb carbon with rubisco
  • Rubisco combines CO2 with RuBP to form 3-carbon molecules called phosphoglycerate (PGA)
• Phase 2: Carbon reduction

  • PGA converted to G3P using NADPH and ATP
  • For every 6 turns of the Calvin cycle, 2 G3P molecules are used in carbohydrate synthesis
• Phase 3: RuBP regeneration

  • 10 G3Ps remain containing 30 carbon atoms, rearranged into 6 molecules of 5-carbon compound ribulose phosphate (RP)
  • ATP from light-dependent reactions is used to add a second phosphate to ribulose phosphate
• C4 Pathway Examples: crabgrass, corn, sugarcane

  • 4-carbon compound is transported to bundle sheath cells where CO2 is fixed into sugar by the regular C3 pathway
• CAM Pathway Example: Desert plants

  • CAM plants fix CO2 during the night, temporarily storing it in vacuoles before fixing it into sugar by the usual pathway
• Cellular respiration is a series of chemical reactions that break apart fuel molecules and transfer the energy stored in their bonds to ATP for cellular work
• Aerobic respiration is the process where cells use oxygen to break down organic molecules, releasing energy for biological work
• Aerobic respiration has 4 stages: Glycolysis, Formation of Acetyl CoA, Citric acid cycle, and Electron transport and chemiosmosis
• Tricarboxylic acid cycle
• First step: Acetyl CoA joins with oxaloacetate to form citrate

  • Citrate is converted into isocitrate in a two-step process
• Second step: Isocitrate is oxidized, releasing a molecule of carbon dioxide and forming ketoglutarate

  • NAD+ is reduced to form NADH during this step
• Step 3: Ketoglutarate is oxidized, reducing NAD+ to NADH and releasing a molecule of carbon dioxide

  • The remaining 4-carbon molecule forms succinyl CoA
• Step 4: Similar to the third step, a-ketoglutarate is oxidized, reducing NAD+ to NADH and releasing a molecule of carbon dioxide

  • The remaining 4-carbon molecule picks up Coenzyme A to form succinyl CoA
• Include aerobic respiration, anaerobic respiration, and fermentation