Bioenergetics

• What absorbs the energy required for photosynthesis?

  Chlorophyll
• In what part of the cell does photosynthesis take place?

  In chloroplasts
• What is the word equation for photosynthesis? 

  Carbon dioxide + water ➔ glucose + oxygen
• What is the chemical symbol equation for photosynthesis?

  6CO2 + 6H2O ➔ C6H12O6 + 6O2
• Photosynthesis is an endothermic process because it requires energy (from the sun).
• What can the glucose made during photosynthesis be used for?

  • Respiration
  • Stored as starch for later
• How do plants get the carbon dioxide required for photosynthesis? 

  It diffuses from the air into the leaves via stomata 
• How do plants get the water required for photosynthesis? 


  It diffuses from the soil into the root hair cells by osmosis
• What makes starch a useful long term storage molecule?

  It is compact 

  It requires energy to make

  It can easily be broken down when needed 
• What do plants need to make amino acids?

  • Glucose
  • Nitrate ions
• What are the main uses of glucose in plants? 

  • Cellular respiration - break down the glucose to release energy 
  • Make cellulose - which is used to make strong cell walls
  • Make starch - which is used to store glucose for a later time
  • Make amino acids - which are used to make proteins 
  • Make lipids - these store the energy as fats or oils for later use
• Photosynthesis converts light energy from the sun into chemical energy in the chemical bonds of glucose molecules. 
• Why may plants produce insufficient chlorophyll?

  • They lack the required nutrients 
  • They have a disease like Tobacco Mosaic Virus or Rose Black Spot
• What are the five factors that effect the rate of photosynthesis?

  • Light intensity 
  • Amount of carbon dioxide
  • Temperature 
  • Amount of chlorophyll
  • Amount of water
• Given the shape of the graph above, which variable(s) could be on the x axis?

  Carbon dioxide concentration 

  Light intensity 

  
• What factor would be on the x axis

  Temperature

  
• We can see that the rate of photosynthesis is no longer increasing as light intensity increases. This means that another factor (such as carbon dioxide or temperature) must be limiting the rate.

  
• Describe and explain how the rate of photosynthesis varies with temperature?

   

  At first the rate of photosynthesis rises with temperature as the particles have more energy and move more quickly. This means they can react more quickly and so the rate is higher.

  However, as temperature rises above the optimum temperature for the enzymes involved, the enzymes may start to break down. This decreases the rate until it falls to zero (when the enzymes are denatured).
• Farmers in cooler climates often use greenhouses. These help trap the heat energy from sunlight, and so increase the temperature. They also keep out pests which could otherwise damage the plants. 
• How can farmers ensure that photosynthesis takes place 24 hours a day?

  Artificial lighting
• Paraffin heaters have two benefits:

  • Increase temperature
  • Produce lots of CO2
• Respiration is the release of energy from sugar molecules such as glucose.
• Is respiration an exothermic or endothermic reaction?

  Respiration is an exothermic reaction because it involves the release of energy. 
• What are examples of how cells use the energy from respiration.

  To combine small molecules to make larger molecules

  To break large molecules into smaller molecules

  For muscle contraction

  To maintain our body temperature

  To move substances around the cell
• What is metabolism?

  The combination of all chemical reactions in an organism 
• What is the word equation for aerobic respiration? 

  Glucose + oxygen ➔ carbon dioxide + water
• What is glucose converted to during anaerobic respiration in animals?

  Lactic acid
• Complete the word equation for anaerobic respiration in plants and fungi:

  Glucose ➔ ethanol + carbon dioxide
• What are the two reasons animals cells prefer aerobic respiration to anaerobic respiration?

  Anaerobic respiration doesn't break down the glucose molecule completely, and so releases less energy than aerobic respiration

  Anaerobic respiration produces lactic acid which can damage cells and leads to an oxygen debt
• 1. In order to move during exercise, we have to contract and relax our muscles. 
  2. Muscular contraction requires energy though, which has to be released by cellular respiration. 
  3. Most of the time cells carry out aerobic respiration, which is far more efficient but requires oxygen. 
  4. This means that we have to pump oxygen around the body faster when we exercise. 
  5. As a result we increase both our heart rate and our breathing rate.
• Anaerobic respiration leads to the build up of lactic acid and oxygen debt
• Which organ in the body removes the lactic acid from the blood?

  Liver
• To measure a persons breathing rate, we can count how many times their chest rises and falls in a given amount of time.