Bioenergetics

• Light intensity equation


  Light intensity = 1/(distance)^2
• Photosynthesis word equation


  carbon dioxide + water --> glucose and oxygen
• Photosynthesis balanced symbol equation

  6CO2 + 6H2O ------> C6H12O6 + 6O2
• Limiting factor


  A factor that affects the rate of photosynthesis
• Endothermic reaction


  A reaction that takes in energy from the surroundings
• Glucose


  A simple sugar that is an important source of energy.
• Where does photosynthesis occur

  Chloroplast
• Why does photosynthesis occur

  All organisms need food (glucose) for respiration, growth, and reproduction

  Plants (and algae) make food by photosynthesis
• Photosynthesis process


  1. Energy is transferred from the environment to the chloroplasts by light

  2. The by-product (oxygen) is released into the air - you can then breathe it in
• How are leaves adapted for photosynthesis

  Thin - so diffusion distances for gases are short

  Guard cells - open and close stomata to regulate gas exchange

  Broad - big surface area for light to fall on

  Veins (xylem and phloem) - these carry water to or glucose away from the cells and also support leaves

  Chlorophyll - in the chloroplasts allows the leaf to absorb light

  Air spaces- allow carbon dioxide to get into the cells, and oxygen to leave by diffusion
• The inverse square law

  As distance from plant increases, light intensity decreases - inverse relationship. The light intensity decreases in inverse

  proportion to the square of the distance - doubling the distance results in the light intensity decreasing by a quarter
• Limiting factors of photosynthesis

  Light intensity

  Carbon dioxide concentration

  Temperature
• Hydroponics system


  Plants grown in water with a perfect balance of nutrients
• Effect of temperature on the rate of photosynthesis

  The temperature of the environment affects how much kinetic energy all particles have - so temperature affects the speed at which carbon dioxide and water move through a plant

  The lower the temperature, the less kinetic energy particles have, resulting in fewer successful collisions occurring over a period of time

  Increasing temperature increases the kinetic energy of particles, increasing the likelihood of collisions between reactants and enzymes which results in the formation of products

  At higher temperatures, however, enzymes that control the processes of photosynthesis can be denatured (where the active site changes shape and is no longer complementary to its substrate) - this reduces the overall rate
• Effect of light intensity on the rate of photosynthesis

  The intensity of the light available to the plant will depend on the amount of energy that it has to carry out photosynthesis

  The more light a plant receives, the faster the rate of photosynthesis

  This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
• Effect of CO₂ on the rate of photosynthesis

  Carbon dioxide is one of the raw materials required for photosynthesis

  This means the more carbon dioxide that is present, the faster the reaction can occur

  This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
• Effect of the amount of chlorophyll on the rate of photosynthesis

  The number of chloroplasts (as they contain the pigment chlorophyll which absorbs light energy for photosynthesis) will affect the rate of photosynthesis

  The more chloroplasts a plant has, the faster the rate of photosynthesis

  The amount of chlorophyll can be affected by:diseases (such as tobacco mosaic virus)lack of nutrients (such as magnesium)loss of leaves (fewer leaves means fewer chloroplasts)
• Limiting factors of photosynthesis (greenhouse)


  Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit.
• Use of 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 the cell wall

  used to produce amino acids for protein synthesis

  To produce proteins, plants also use nitrate ions that are absorbed from the soil.
• cellular respiration


  process that releases energy from food in the presence of oxygen
• What do organisms need respiration for

  chemical reactions to build larger molecules

  movement

  keeping warm
• aerobic respiration equation


  glucose + oxygen -> carbon dioxide + water
• Anaerobic respiration equation


  glucose --> lactic acid
• anaerobic respiration equation in plant and yeast cells (fermentation)


  glucose --> ethanol + carbon dioxide
• Body's response to an increased demand of energy

  The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood. If insufficient oxygen is supplied 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.
• Response to exercise

  Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
• Metabolism


  All of the chemical reactions that occur within an organism. The energy transferred by respiration in cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules.
• What does metabolism include

  - conversion of glucose to starch, glycogen and cellulose

  - the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids

  - the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins

  - respiration

  - breakdown of excess proteins to form urea for excretion