Bioenergetics

• What is photosynthesis?


  The process by which plants synthesise glucose using light energy from the sun

  Light energy if converted into chemical energy
• Where does photosynthesis take place?

  Within the chloroplasts in leaf palisade cells

  They contain chlorophyll, a pigment which absorbs light energy
• State the equations for photosynthesis:

  Carbon dioxide + water -> glucose + oxygen

  6CO2 + 6H2O + C6H12O6 + 6O2
• Is photosynthesis endothermic or exothermic?

  Endothermic

  -> energy is transferred from the environment to chloroplasts by light
• How can you show that a plant gives off oxygen during photosynthesis?

  Using a water pant collect gas bubbles produces during photosynthesis

  The gas will relight a glowing splint
• Give examples of leaf adaptations which maximise the rate of photosynthesis:

  > Broad leaves: maximise surface area

  > Thin leaves: short diffusion distance

  > Veins: Transport water to leaves via xylem, remove photosynthesis products via phloem

  > Guard cells: control opening of stomata for gaseous exchange and prevent water loss
• What are the 4 main factors that affect the rate of photosynthesis?

  Temperature

  Light intensity

  Carbon dioxide concentration

  Amount of chlorophyll
• How does temp affect the rate of photosynthesis?

  Increases temp increases rate of photosynthesis as the kinetic energy of particles is increases

  The rate decreases past a certain temp as enzymes become denatured
• How does light intensity affect the rate of photosynthesis?

  Increasing light intensity increases the rate of photosynthesis because if there is more light, more photosynthesis can occur
• Uses of glucose produced during photosynthesis:

  Respiration

  Starch for storage

  Cellulose for strength

  Amino acid 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 which can be used by cells
• What are the equations for aerobic respiration?

  Glucose + oxygen -> carbon dioxide + water

  C12H12O6 + 6O2 -> 6CO2 + 6H2O
• Where does aerobic respiration take place?

  Mitochondria
• Why do organisms require the energy released by respiration?

  Synthesis of larger molecules

  Muscle contraction

  Maintenance of body temp

  Active transport
• What is anaerobic respiration?

  An exothermic reaction in which glucose is broken down to release 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?

  Glucose is not completely broken down so less energy is transferred
• Why can anaerobic respiration lead to muscle fatigue?

  Lactic acid (the product of anaerobic respiration) builds but in muscles preventing efficient contraction
• What is 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 that occurs in yeast cells
• What is the equation for fermentation?

  Glucose -> ethanol + carbon dioxide
• How do muscles store glucose?

  As glycogen
• What changes take place when muscular activity increases in the body?

  > Heart rate increases and arteries dilate: increases flow of oxygenated blood to muscles

  > Breathing rate increases and breathing is deeper: increases rate of gaseous exchange

  > Stored glycogen is converted back into glucose
• How is lactic acid transported away from the muscles?

  Blood flow though 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
• Give examples of metabolic reactions:

  > Glucose into starch/glycogen/cellulose

  > Glycerol and fatty acids into lipids

  > Glucose into amino acids

  > Photosynthesis and respiration

  > Breakdown of excess proteins into urea