Bioenergetics

• What is the word and symbol equation for photosynthesis?


  Carbon dioxide + Water → Glucose + Oxygen

   6CO2 + 6H2O → C6H12O6 + 6O2
• What type of reaction is photosynthesis?

  • An endothermic reaction
  • Energy is transferred from the environment to the chloroplasts by light.
• What is the glucose produced in photosynthesis used for?

  • respiration
  • converted into insoluble starch for storage
  • used to produce fat or oil for storage
  • used to produce cellulose, which strengthens cell walls
  • used to produce amino acids for protein synthesis
• Which factors affect the rate of photosynthesis?

  • Light intensity
  • Temperature
  • Carbon dioxide concentration
  • Amount of chlorophyll
• What is the purpose of the required practical described in the study material?

  To investigate the effect of light intensity on the rate of photosynthesis using pondweed.
• How far should the boiling tube be placed from the light source at the start?

  10 cm
• What solution is used to fill the boiling tube?

  Sodium hydrogen carbonate solution
• What should be done with the cut pondweed before starting the experiment?


  Place it in the boiling tube with the cut end at the top
• How long should the boiling tube be left to rest before starting the stopwatch?


  5 minutes
• What is the procedure for measuring the number of bubbles produced?


  Start the stopwatch and count the bubbles produced in 1 minute
• How many times should the bubble count be repeated for each light intensity/distance?


  Twice more
• What should be done with the results of the bubble counts?


  Record them in a table
• What should be done after measuring the bubbles at 10 cm distance?


  Repeat the previous steps for 3 more distances (20, 30, 40 cm)
• What is the final step of the practical after collecting all data?


  Plot a graph
• What is the relationship between light intensity and distance?

  • The light intensity is inversely proportional to the square of the distance - inverse square law.
  • As the distance increases, the light intensity decreases.
• Ways of artificially creating conditions for farming

  • Greenhouses - traps the sun's heat →increases the temperature
  • Artificial light - increases the light intensity → photosynthesis can happen in the night
  • Paraffin heater - increases the level of carbon dioxide in the greenhouse and heats it
• What is respiration?

  • The process of transferring energy from glucose, which goes in every cell.
  • It is an exothermic process
• What do organisms need energy for?

  • Keeping warm
  • Movement
  • Chemical reactions to build larger molecules
• What are the two types of respiration?

  • Aerobic respiration (with oxygen)
  • Anaerobic respiration (without oxygen)
• What is metabolism?

  • Metabolism is the sum of all the reactions in a cell or the body.
  • Metabolism includes: breakdown of excess proteins to form urea for excretion.
• Aerobic respiration

  • Respiration using oxygen
  • Most of the reactions in aerobic respiration happen inside mitochondria
  • The most efficient way to transfer energy from glucose
• What is the equation for aerobic respiration?

  •  glucose + oxygen → carbon dioxide + water 
  • C6H12O6 + 6O2 → 6CO2 + 6H2O 
• Anaerobic respiration

  • Without oxygen
  • As the oxidation of glucose is incomplete, much less energy is transferred than in aerobic respiration
  • Only useful in emergencies
  • Lactic acid builds up, which has to be removed later
• What is the equation for anaerobic respiration in muscles?

  • glucose →lactic acid
• What is the equation for anaerobic respiration in yeast and plant cells?

  • glucose →  ethanol⁢  +  carbon dioxide
• Anaerobic respiration in yeast cells

  • Anaerobic respiration in yeast cells is called fermentation
  • Fermentation by yeast is of great value because it's used to make bread and alcoholic drinks e.g. beer and wine
• What happens when you exercise?

  • Some of your muscles contract more frequently than normal so you need more energy.
  • The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood. This removes carbon dioxide more quickly at the same time.
• What happens if insufficient oxygen is supplied during exercise?

  • Anaerobic respiration takes place in muscles
  • 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.
• What is oxygen debt?

  • The amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells
• What happens to the lactic acid after you stop exercising?

  •  Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose