4 - Bioenergetics

• Write the word equation for photosynthesis

  carbon dioxide + water -(light)-> oxygen + glucose
• Write the symbol equation for photosynthesis

  6 CO2 + 6 H2O -> C6H12O6 + 6 O2
• What type of reaction is photosynthesis?

  Endothermic - energy is transferred from the environment to the chloroplasts by light
• Name 4 factors that can affect the rate of photosynthesis.

  1. Temperature

  2. Light intensity

  3. Carbon dioxide concentration

  4. Amount of chlorophyll
• Draw and explain a graph to show how temperature affects the rate of photosynthesis.

  Temperature increases rate of reaction until optimum temperature is reached, but after 45 degrees C the enzymes controlling photosynthesis are denatured

  
• Draw and explain a graph to show how light intensity affects the rate of photosynthesis.


  For most plants, the brighter the light the faster the rate of photosynthesis

  
• Draw a graph to show how the level of carbon dioxide affects the rate of photosynthesis.


  Only 0.04% carbon dioxide in atmosphere so this is often limiting factor

  
• Describe AND explain the graph of light intensity versus rate of photosynthesis.

  As the light intensity increases the rate of photosynthesis increases until either carbon dioxide concentration or temperature become the limiting factor and the rate of photosynthesis levels off even though the light intensity continues to increase.
• Describe AND explain the graph of carbon dioxide level versus rate of photosynthesis.

  As the CO2 concentration increases the rate of photosynthesis increases until either light intensity or temperature become the limiting factor and the rate of photosynthesis levels off even though the CO2 concentration continues to increase.
• When is chlorophyll a limiting factor of photosynthesis?


  In ornamental plants with variegated (non-green) leaves

  
• Why are limiting factors important in economics?

  Greenhouses want to enhance the conditions to gain the maximum rate of photosynthesis whilst still maintaining profit
• Describe some ways to increase limiting factors in greenhouses

  1. CO2 levels - paraffin heaters

  2. Temperature - (paraffin) heaters, ventilation

  3. Light intensity - artificial light during night
• Describe the relationship between light intensity and distance.

  When the lamp is closer to the plant the light intensity is higher, but as the lamp is moved further away the light intensity decreases
• Name the law that is used to link light intensity and distance.

  INVERSE SQUARE LAW
• Give the equation that shows the relationship between light intensity and distance.

  light intensity ∝ 1 / distance squaredSee an expert-written answer!We have an expert-written solution to this problem!
• How can we measure and calculate rate of photosynthesis

  1. Measure - number of bubbles per minute

  2. Calculate - take 3 readings and a mean to calculate bubbles/min
• Limitations to measuring bubbles as a rate of photosynthesis

  1. Hard to count all the bubbles/bubbles of different sizes

  2. We could improve this by collecting oxygen in a gas syringe

  3. Experiment assumes that all oxygen from photosynthesis is given off - ignores use of oxygen in respiration
• Give 5 uses of the glucose made in photosynthesis.

  RIFOCA

  1. respiration

  2. converted into insoluble starch for storage

  3. used to produce fat or oil for storage

  4. used to produce cellulose which strengthens cell wall

  5. used to produce amino acids for protein synthesis

  
• What do plants use in addition to glucose to produce proteins?

  Nitrate ions that are absorbed from the soil
• What is respiration?


  An exothermic reaction which is. continuously occuring in living cells. The energy transferred supplies all the energy needed for living processes.
• Why is respiration exothermic?

  because it transfers energy to the environment
• What do organisms need energy for? (3)

  1. Chemical reactions to build larger molecules

  2. Movement - to transfer energy to make muscles contract in animals

  3. Keeping warm - in mammals and birds to maintain a constant internal body temperature
• What is aerobic respiration?

  respiration using glucose and oxygen
• What is the word equation for aerobic respiration?

  glucose + oxygen -> carbon dioxide + water (+ ENERGY)
• What is the symbol equation for aerobic respiration?

  C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O (+ ENERGY)
• Where does aerobic respiration mainly occur?

  inside mitochondria
• What is anaerobic respiration?

  respiration without oxygen
• When does anaerobic respiration take place in muscles?

  when you do vigorous exercise and your body is unable to supply oxygen quickly enough
• Which type of respiration transfers the least energy?

  anaerobic respiration transfers much less energy as the oxidation of glucose is incomplete
• Give a word equation for anaerobic respiration in muscles.

  glucose -> lactic acid (+ ENERGY)
• Give a word equation for anaerobic respiration in plants and yeast.

  glucose -> ethanol + carbon dioxide (+ energy transferred to the environment)
• What is anaerobic respiration in yeast cells called?

  Fermentation
• Why is fermentation economically important?

  It helps the manufacture of bread and alcoholic drinks
• During exercise, the human body...

  ...reacts to the increased demand for energy
• Describe what happens to the heart rate, breathing rate and breath volume during exercise and explain why this happens. (5)

  1. They increase

  2. To supply the muscles with more oxygenated blood

  3. For faster rate of respiration

  4. Faster breathing rate and greater breathing volume supplies more oxygen

  5. Faster heart rate pumps blood more quickly to carry oxygen from lungs and glucose to muscles
• What is meant by the term oxygen debt?


  The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from cells
• What happens when insufficient oxygen is supplied during exercise? (3)

  1. Anaerobic respiration takes place in the muscles

  2. The incomplete oxidation of glucose causes a build up of lactic acid

  3. And creates an oxygen debt
• What is the role of blood in removing lactic acid?

  Transports lactic acid to the liver where it is converted back into glucose
• What happens to the muscles during long periods of vigorous activity?

  The muscles become fatigued and stop contracting efficiently
• What is metabolism?


  The sum of all the reactions in a cell or the body