Bioenergetics

• Photosynthesis


  1. Takes place in leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis requires light energy
• Endothermic reaction


  Reaction where energy is transferred from the environment
• How plant gets reactants for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is essential
  • Oxygen is also produced but not as important
• Uses of glucose


  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate often depends on rate of photosynthesis
• Factors affecting rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and amount of chlorophyll
• Factors affecting photosynthesis

  • Light intensity
  • Temperature
  • Concentration of carbon dioxide in the air
  • Amount of chlorophyll in plants
• Chlorophyll

  Pigment within chloroplasts that absorbs the light energy needed for photosynthesis
• Plants have less chlorophyll

  They won't be able to carry out as much photosynthesis
• Different plants will naturally have different amounts of chlorophyll
• The level of chlorophyll within an individual plant can vary due to disease, environmental stress or lack of nutrients
• Factors that damage chloroplasts and reduce chlorophyll production include disease, environmental stress, and lack of nutrients
• Limiting factors for photosynthesis

  • Light
  • Carbon dioxide
  • Temperature
• Graphing limiting factors for photosynthesis

  1. Plot light intensity on x-axis

  2. Plot rate of photosynthesis on y-axis
• As light intensity increases

  The rate of photosynthesis increases
• The line flattens out when something else becomes the limiting factor, such as carbon dioxide concentrations or temperature
• As carbon dioxide concentration increases

  The rate of photosynthesis increases
• As temperature increases

  The rate of photosynthesis increases initially
• As temperature continues to increase

  The rate of photosynthesis starts to drop as enzymes denature
• At around 45 degrees, the enzymes are fully denatured and the rate of photosynthesis falls to zero
• Graphs can show multiple limiting factors, such as different temperatures or carbon dioxide concentrations
• Strategies farmers use to optimize photosynthesis

  • Use greenhouses to trap heat and provide artificial light
  • Pump in carbon dioxide
  • Use paraffin heaters for heat and CO2
  • Use fertilizers for essential minerals
  • Use pesticides to control pests
• Optimizing photosynthesis conditions can be costly for farmers, so they have to weigh the extra cost against the expected yield increase
• Cellular respiration is an exothermic reaction which transfers energy from glucose and is continuously occurring in living cells
• Cellular respiration

  Breaking apart glucose molecules to release the energy that's trapped inside
• How organisms use their energy

  • Building up larger molecules from smaller ones (e.g. combining amino acids to form proteins)
  • Muscular contraction for movement
  • Maintaining body temperature
• Energy is needed for loads of reactions in our cells, most of which are catalyzed by enzymes
• Metabolism

  All the chemical processes that occur within a living organism in order to maintain life
• Aerobic respiration

  • More common type
  • Takes place whenever there's enough oxygen
  • Most efficient way to transfer energy from glucose
  • Takes place continuously in both plants and animals
  • Takes place within mitochondria
• Aerobic respiration

  Glucose + Oxygen → Carbon dioxide + Water
• The equation for aerobic respiration is the opposite of the equation for photosynthesis
• Anaerobic respiration

  • Respiration without oxygen
  • Used when there's not enough oxygen to keep up with the demands of aerobic respiration
  • Incomplete breakdown of glucose molecule
  • Leads to lactic acid buildup
• Anaerobic respiration

  Glucose → Lactic acid
• Anaerobic respiration in plants and yeast

  • Glucose is converted to ethanol and carbon dioxide instead of lactic acid
  • In yeast, this process is called fermentation
  • Used to make bread, beer, and wine
• Exercise

  Requires our bodies to carry out more cellular respiration
• Cellular respiration during exercise

  1. Muscles require more energy

  2. Muscles require more oxygen

  3. Breathing rate and volume increase

  4. Heart rate increases
• Insufficient oxygen during intense exercise

  Cells use anaerobic respiration
• Anaerobic respiration

  Less efficient than aerobic respiration, produces lactic acid