4: bioenergetics

• What is the word equation for photosynthesis?

  Carbon dioxide + water -> glucose + oxygen
• What is this? : C₆H₁₂O₆

  Glucose
• What is this? H₂O

  Water
• What is this? O₂

  Oxygen
• What kind of reaction is photosynthesis?

  Endothermic

  Energy is transferred from the environment to the chloroplasts by light
• What does the photosynthesis rate/temperature graph look like?

  
• Explain the shape of the photosynthesis rate/temperature graph

  -Higher temp -> faster rate of reaction -> more photosynthesis

  
  

  -Optimum temperature -> the most photosynthesis

  
  

  -Too hot -> enzymes denature -> photosynthesis slows
• What does the photosynthesis rate/light graph look like?

  
• Explain the shape of the photosynthesis rate/light graph

  -More light -> more photosynthesis

  
  

  -Reaches top and plateaus (stays the same)

  
  

  -Something else (eg temp, carbon dioxide) is limiting the rate of photosynthesis
• How does amount chlorophyll affect the rate of photosynthesis?


  -More chlorophyll -> more photosynthesis

  
  

  -Same as light/carbon dioxide - eventually, something else will limit the rate.
• Explain the shape of the photosynthesis rate/carbon dioxide graph

  -More carbon dioxide -> more photosynthesis

  
  

  -Reaches top and plateaus (stays the same)

  
  

  -Something else (eg temp, light) is limiting the rate of photosynthesis
• What does the photosynthesis rate/carbon dioxide graph look like?

  
• [HT only] What is the inverse square law?

  As the distance increases, light intensity decreases

  
• [HT only] What is the inverse square law equation?

  
• [HT only] Why are limiting factors important in greenhouses?

  To gain the maximum rate of photosynthesis

  Still maintain a profit
• What is glucose used for in a plant?

  • respiration

  • converted into insoluble starch for storage

  • produce fat or oil for storage

  • produce cellulose, which strengthens the cell wall

  • produce amino acids for protein synthesis.
• What do plants need to produce proteins?

  Nitrate ions absorbed from the soil
• What is cellular respiration?

  Exothermic reaction

  Releases energy

  Continuously occurring in living cells
• What do organisms need energy for?

  • chemical reactions to build larger molecules

  • muscle contraction for movement

  • keeping warm
• What are the two ways that respiration can take place?

  Aerobically

  Anaerobically
• What is the equation for aerobic respiration?

  glucose + oxygen -> carbon dioxide + water
• What is the equation for anaerobic respiration in muscles?

  glucose -> lactic acid
• What is the equation for anaerobic respiration in plants and yeast?

  glucose --> ethanol + carbon dioxide
• What is anaerobic respiration in yeast called and why is it important?

  Fermentation

  Manufacture of bread and alcoholic drinks
• What is the difference between aerobic and anaerobic resorption in terms of the need for oxygen?

  Aerobic - requires oxygen

  Anaerobic - takes place without oxygen
• What is the difference between aerobic and anaerobic resorption in terms of the products?

  Aerobic - produces carbon dioxide and water

  Anaerobic (muscles) - produces lactic acid

  Anaerobic (yeast/plants) - produces ethanol and carbon dioxide
• What is the difference between aerobic and anaerobic resorption in terms of the energy transferred?

  Aerobic respiration transfers more energy
• How does the human body react to exercise?

  The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
• What happens in the body due to anaerobic respiration?

  The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt.

  
  

  During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
• [HT only] What is oxygen debt?

  The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.

  
  

  Lactic acid is transported from the muscles to the liver by blood to be converted back into glucose.
• What is metabolism?

  The sum of all the reactions in a cell or the body.

  Controlled by enzymes
• What does metabolism involve?

  • conversion of glucose to starch, glycogen and cellulose

  • the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids

  • the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins

  • respiration

  • breakdown of excess proteins to form urea for excretion.