B4 bioenergetics

• Photosynthesis is the process by which plants make glucose from sunlight
• Photosynthesis is an endothermic reaction where energy is transferred from the environment to the chloroplasts by light
• The equation for photosynthesis is: light + carbon dioxide + water → glucose + oxygen
• Factors affecting the rate of photosynthesis:

  • Temperature: Increasing temperature increases the rate of photosynthesis until enzymes denature
  • Light intensity: Higher light intensity leads to a faster reaction
  • Carbon dioxide concentration: Increasing concentration increases the rate of reaction
  • Amount of chlorophyll: Essential for converting light energy to food for the plant
• Experiment to measure the rate of photosynthesis:

  • Oxygen production of a plant is measured
  • Variables that can be changed include temperature, time, and light intensity
  • Limiting factors can restrict the rate of photosynthesis despite other factors increasing
• Light intensity is measured in lux

  • Limiting factors can be identified in graphs
  • Farmers can use knowledge of limiting factors to enhance conditions for greater photosynthesis
• Uses of glucose from photosynthesis:

  1. For respiration

  2. Converted into insoluble starch for storage

  3. To produce fat or oil for storage

  4. To produce cellulose to strengthen cell walls

  5. Combined with nitrates to form amino acids for proteins
• Respiration is the process of transferring energy from glucose for living processes

  • It can occur aerobically (with oxygen) or anaerobically (without oxygen)
• Response to exercise:

  • During exercise, more energy is needed for muscle contraction
  • Aerobic respiration uses oxygen and yields the most energy
  • Anaerobic respiration occurs when there is not enough oxygen and does not yield as much energy
• Anaerobic respiration:

  • Lactic acid is a byproduct
  • Oxygen debt occurs when lactic acid builds up
  • Metabolism is the sum of all reactions in a cell or body, controlled by enzymes
• Metabolism


  Defined as the sum of all the chemical reactions in an organism
• Reactions for metabolism include

  1. Multiple GLUCOSE molecules joining to form STARCH and CELLULOSE in plants, and GLYCOGEN in animals.

  2. Forming LIPIDS from ONE molecule of GLYCEROL and THREE molecules of FATTY ACIDS.

  
  

  3. Forming AMINO ACIDS by combining GLUCOSE with NITRATE IONS to produce PROTEINS.

  
  

  4. Breaking down GLUCOSE via RESPIRATION for TRANSFERRING ENERGY to power ALL reactions in the body.

  
  

  5. Breaking down EXCESS PROTEIN into UREA for EXCRETION.
• Oxygen Debt

  • After the exercise is finished, your body has an OXYGEN DEBT that must be repaid to clear the LACTIC ACID that has built up.To repay the OXYGEN DEBT, breathing and heart rate remains HIGH even AFTER stopping the exercise.
  • LACTIC ACID is transported to the LIVER to be converted back into GLUCOSE.

   
• Exercise

  • MUSCLES contract more during exercise, requiring more ENERGY from increased RESPIRATION.
  • To supply OXYGEN for respiration, your BREATHING RATE, BREATH VOLUME and HEART RATE all increase.
  • If the exercise is VIGOROUS like sprinting, the elevated breathing and heart rate does not provide ENOUGH oxygen for aerobic respiration so ANAEROBIC RESPIRATION takes place.
  • This leads to MUSCLE FATIGUE and LACTIC ACID build up which causes the body pain and can lead to inefficiency in MUSCLE CONTRACTIONS due to fatigue.