photosynthesis and respiration

• All organisms need energy for life processes (and you need some for revising, so it's pretty important)
• Plant and animal cells need energy for biological processes to occur
• Things plants need energy for

  • Photosynthesis
  • Active transport to take in minerals via their root
  • DNA replication
  • Cell division
  • Protein synthesis
• Things animals need energy for

  • Muscle contraction
  • Maintenance of body temperature
  • Active transport
  • DNA replication
  • Cell division
  • Protein synthesis
• Photosynthesis


  1. Energy from light is used to make glucose from CO2 and H2O

  2. The light energy is converted to chemical energy in the form of glucose
• The overall equation for photosynthesis is: CO2 + H2O + Energy -> C6H12O6 (glucose) + 6O2
• Energy is stored in the glucose until the plants release it by respiration
• Animals obtain glucose by eating plants or other animals, then respire the glucose to release energy
• Respiration


  1. Plant and animal cells release energy from glucose

  2. This energy is used to power all the biological processes in a cell
• Types of respiration


  • Aerobic respiration (using oxygen)
  • Anaerobic respiration (without oxygen)
• Aerobic respiration produces CO2 and H2O and releases energy. The overall equation is: C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy
• Anaerobic respiration in plants and yeast produces ethanol and CO2 and releases energy
• In humans, anaerobic respiration produces lactate and releases energy
• ATP


  The immediate source of energy in a cell
• ATP synthesis


  1. Energy released from glucose is used to make ATP via a condensation reaction between ADP and inorganic phosphate

  2. ATP synthase catalyses this reaction
• ATP hydrolysis


  1. ATP is hydrolysed back into ADP and inorganic phosphate

  2. Chemical energy is released from the phosphate bond and used by the cell

  3. ATP hydrolase catalyses this reaction
• ATP


  • Stores or releases only a small, manageable amount of energy at a time
  • Is a small soluble molecule so it can be easily transported and the cell can easily break it down
  • Can be quickly re-made
  • Can make other molecules more reactive by transferring one of its phosphate groups
• Metabolic pathway


  A series of small reactions controlled by enzymes, e.g. respiration and photosynthesis
• Phosphorylation


  Adding phosphate to a molecule, e.g. ADP is phosphorylated to ATP
• Photophosphorylation


  Adding phosphate to a molecule using light
• Photolysis


  The splitting (lysis) of a molecule using light
• Photoionisation


  When light energy excites electrons in an atom or molecule, giving them more energy and causing them to be released, the release of electrons causes the atom or molecule to become a positively-charged ion
• Hydrolysis


  The splitting (lysis) of a molecule using water
• Decarboxylation


  The removal of carbon dioxide from a molecule
• Dehydrogenation


  The removal of hydrogen from a molecule
• Redox reactions


  Reactions that involve oxidation and reduction
• Coenzyme


  A molecule that aids the function of an enzyme
• Coenzymes used in photosynthesis


  • NADP
• Coenzymes used in respiration


  • NAD
  • Coenzyme A
  • FAD
• NADP transfers hydrogen from one molecule to another, so it can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule
• NAD and FAD transfer hydrogen from one molecule to another, so they can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule
• Coenzyme A transfers acetate between molecules
• Photosynthesis Takes Place in the Chloroplasts of Plant Cells
• Chloroplasts


  • Surrounded by a double membrane
  • Found in plant cells
• Structure of chloroplasts


  1. Thylakoid membrane

  2. Stacked into grana

  3. Stroma
• Chlorophyll


  Pigment that absorbs light energy for photosynthesis
• Photosynthesis can be Split into Two Stages
• Light Dependent Reaction


  1. Light energy excites electrons in chlorophyll

  2. Electron transport chain

  3. ATP and reduced NADP produced
• Light Independent Reaction (Calvin Cycle)


  1. Uses ATP and reduced NADP from light dependent reaction

  2. Converts CO2 to simple sugars
• Non-cyclic Photophosphorylation


  1. Light energy excites electrons

  2. Electron transport chain

  3. Proton gradient formed

  4. ATP produced by ATP synthase