Topic 5 – Energy Transfers In & Between Organisms

• What is photosynthesis?

  A reaction using light energy to produce glucose
• What are the reactants required for photosynthesis?

  Water and carbon dioxide
• What are the products of photosynthesis?

  Glucose and oxygen
• What are the two stages of photosynthesis?

  • Light dependent stage
  • Light independent stage
• What factors determine the rate of photosynthesis?

  Carbon dioxide concentration, light intensity, temperature
• Where does photosynthesis occur in plants?

  • In chloroplasts
• How are chloroplasts adapted for photosynthesis?

  • Stacks of thylakoid membranes (grana) for surface area
  • Specific protein network to hold chlorophyll
  • ATP synthase channels for ATP synthesis
  • Contain DNA and ribosomes for protein synthesis
• What are grana in chloroplasts?

  Stacks of thylakoid membranes
• What is photoionisation in photosynthesis?

  Excitation of electrons in chlorophyll by light
• What is photolysis?

  Splitting of water using light
• How many photons are required to split one molecule of water?

  4 photons
• What are the products of photolysis?

  Oxygen, protons, and electrons
• What happens to the electrons lost from chlorophyll during photolysis?

  They are replaced by electrons from water
• What is the role of the excited electron in the light-dependent reaction?

  It moves down protein complexes to pump protons
• What is the function of ATP synthase in photosynthesis?

  To synthesize ATP from ADP and Pi
• What are the main steps of the light-dependent reaction?

  1. Photoionisation of chlorophyll
  2. Photolysis of water
  3. Electron transport and proton pumping
  4. Formation of reduced NADP
  5. Photophosphorylation to produce ATP
• What is carbon dioxide fixation in the light-independent reaction?

  Carbon dioxide combines with RuBP to form glycerate-3-phosphate
• What enzyme is required for carbon dioxide fixation?

  Rubisco
• What is produced during the reduction phase of the light-independent reaction?

  Triose phosphate from glycerate-3-phosphate
• How is ribulose bisphosphate regenerated in the light-independent reaction?

  Using triose phosphate and ATP
• What can two molecules of triose phosphate form?

  Fructose 1,6 bisphosphate
• How many turns of the Calvin Cycle are needed to produce one glucose molecule?

  6 turns
• What is aerobic respiration?

  Splitting a respiratory substrate with oxygen
• What is anaerobic respiration?

  Respiration occurring without oxygen
• What are the steps in respiration?

  1. Glycolysis
  2. Link Reaction
  3. Krebs Cycle
  4. Oxidative Phosphorylation

  
• Where does glycolysis occur?

  In the cytoplasm of the cell
• What are the products of glycolysis from one glucose molecule?

  2 pyruvate, 2 ATP, 2 NADH
• What happens to pyruvate in anaerobic respiration?

  It is converted into lactate
• What occurs during the link reaction?

  Pyruvate is converted to acetyl coenzyme A
• What is produced in the Krebs Cycle per glucose molecule?

  2 ATP, 6 NADH, 2 FADH, 4 CO2

  
• What is oxidative phosphorylation?

  • Process where reduced NAD and FAD release electrons
  • Electrons pass through protein complexes
  • Protons are pumped to create a gradient
  • ATP is produced via ATP synthase

  
• What is the final electron acceptor in oxidative phosphorylation?

  Oxygen
• What is the proton motive force?

  Energy created by the proton gradient
• What is an ecosystem?

  • Community of organisms in an area
  • Non-living elements of the environment
• What factors control the distribution of organisms in a habitat?

  Biotic and abiotic factors
• What are autotrophs?

  Organisms that produce their own food
• What are heterotrophs?

  Organisms that cannot synthesize their own food
• What percentage of energy is passed on in food chains?

  10%
• What are the ways energy is lost in food chains?

  • Uneaten parts
  • Decay of dead material
  • Excretion
  • Exothermic reactions
• How is energy transfer efficiency calculated?

  Percentage efficiency = (energy transferred / energy input) x 100