1.4 Bioenergetics

• What is photosynthesis?


  The process by which plants synthesize glucose using light energy from the Sun.
• How is light energy transformed during photosynthesis?

  Light energy is converted into chemical energy.
• Where does photosynthesis take place in plants?

  Within chloroplasts in leaf palisade cells.
• What pigment is responsible for absorbing light energy in chloroplasts?

  Chlorophyll.
• What is the word equation for photosynthesis?

  Carbon dioxide + water → glucose + oxygen.
• What is the symbol equation for photosynthesis?

  $6CO_2 +$$6H_2O \rightarrow C_6H_{12}O_6 +$$6O_2$
• Is photosynthesis an endothermic or exothermic reaction?

  Photosynthesis is an endothermic reaction.
• Why is photosynthesis considered an endothermic reaction?

  Energy is transferred from the environment to chloroplasts by light.
• How can you demonstrate that a plant gives off oxygen during photosynthesis?

  By collecting gas bubbles produced by a water plant like Elodea, which will relight a glowing splint.
• What are some leaf adaptations that maximize the rate of photosynthesis?

  • Broad leaves maximize surface area.
  • Thin leaves reduce diffusion distance.
  • Chlorophyll traps light energy.
  • Veins transport water and remove products.
  • Air spaces allow gas exchange.
  • Guard cells control stomata opening.
• What are the four main factors that affect the rate of photosynthesis?

  Temperature, light intensity, carbon dioxide concentration, and amount of chlorophyll.
• How does temperature affect the rate of photosynthesis?

  Increasing temperature increases the rate until enzymes become denatured.
• How does light intensity affect the rate of photosynthesis?

  Increasing light intensity increases the rate until another factor becomes limiting.
• How does carbon dioxide concentration affect the rate of photosynthesis?

  Increasing carbon dioxide concentration increases the rate until another factor becomes limiting.
• How does the amount of chlorophyll affect the rate of photosynthesis?

  Decreasing chlorophyll decreases the rate of photosynthesis.
• What is a limiting factor in photosynthesis?

  An environmental factor that restricts the rate of photosynthesis.
• How can you calculate the rate of photosynthesis by measuring oxygen production?

  1. Set up a bubble potometer with pondweed in water.
  2. Oxygen causes a bubble in the capillary tube to move.
  3. Measure the distance moved to calculate oxygen volume.
• How can farmers use their knowledge of limiting factors to increase profits?

  By controlling temperature, light intensity, and CO2 concentration for optimal photosynthesis.
• What is the relationship described by the inverse square law?

  Light intensity is inversely proportional to the square of the distance.
• What are five uses of glucose produced during photosynthesis?

  • Respiration
  • Starch for storage
  • Cellulose for strength
  • Amino acids and protein synthesis
  • Lipids for energy storage in seeds
• What is aerobic respiration?

  An exothermic reaction in which glucose reacts with oxygen to release energy.
• What is the word equation for aerobic respiration?

  Glucose + oxygen → carbon dioxide + water (+energy)
• What is the symbol equation for aerobic respiration?

  C$_6$H$_{12}$O$_6$ + 6O$_2$ → 6CO$_2$ + 6H$_2$O (+energy)
• Where does aerobic respiration take place?

  In the mitochondria
• Why do organisms require the energy released by respiration?

  For synthesis of larger molecules, muscle contraction, maintenance of body temperature, and active transport.
• What is anaerobic respiration?

  • An exothermic reaction
  • Glucose is broken down
  • Releases energy in the absence of oxygen
• What is the equation for anaerobic respiration?

  Glucose → lactic acid (+energy)
• Why is anaerobic respiration less efficient than aerobic respiration?

  Because glucose is not completely broken down, so less energy is transferred.
• Why can anaerobic respiration lead to muscle fatigue?

  Lactic acid builds up in muscles, preventing efficient contraction.
• What is an oxygen debt?

  The amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration.
• What is fermentation?

  • A type of anaerobic respiration
  • Occurs in yeast cells
• What is the equation for fermentation?

  Glucose → ethanol + carbon dioxide (+energy)
• What are the differences between aerobic and anaerobic respiration?

  • Aerobic requires oxygen; anaerobic does not.
  • Aerobic produces CO$_2$ and water; anaerobic produces lactic acid or ethanol + CO$_2$.
  • Aerobic transfers a greater amount of energy.
• How do muscles store glucose?

  As glycogen
• Why is the fermentation reaction important?

  It is used in the production of bread and alcoholic drinks.
• What changes take place when muscular activity increases in the body?

  • Heart rate increases and arteries dilate.
  • Breathing rate increases and breathing is deeper.
  • Stored glycogen is converted back into glucose.
• How is lactic acid transported away from the muscles?

  Blood flow through the muscles transports lactic acid to the liver, where it is oxidised back to glucose.
• What is metabolism?

  The sum of all the reactions that take place in a cell or an organism.
• How do cells use the energy transferred by respiration?

  To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules.
• Give examples of metabolic reactions.

  • Glucose into starch/glycogen/cellulose
  • Glycerol and fatty acids into lipids
  • Glucose and nitrate ions into amino acids
  • Photosynthesis
  • Respiration
  • Breakdown of excess proteins into urea