Exercise

• Exercise involves your MUSCLE cells working harder than they normally do. The "work" they do is contracting and relaxing. In order to work they need to release energy
• During exercise, the rate of respiration in our muscle cells increases because our cells are working harder
• During exercise, the amount of glucose in out blood decreases because it is used in respiration
• During exercise, our breathing rate (and depth) increases to take in more oxygen and get rid of more carbon dioxide
• During exercise, we produce more carbon dioxide since aerobic respiration produces carbon dioxide
• During exercise, out heart rate increases since respiration releases thermal energy (exothermic)
• During exercise, the amount we sweat increases to help us lose heat (evaporative cooling)
• Give a reason why long distance runners use sugar rich gels part way through their race (1)

  To replace the glucose that has been used in respiration
• Caffeine is a stimulant drug that increases the heart rate. Professional athletes are tested for the presence of caffeine during times of competition. Athletes with levels that exceed the permitted levels are not allowed to compete. Explain why (2)

  Increased heart rate means the rate of respiration increases, this means that more oxygen and glucose can be supplied so cells can continue to release energy
• Explain why the consequence of a faulty valve in the left side of the heart. (You need to link this to the composition of the blood leaving the left side) (4)

  A faulty valve can lead to backflow meaning blood goes through the wrong ways, reducing the amount of blood leaving the left side of the heart, meaning less blood would be delivered to cells of the body, causing less oxygen and glucose to be delivered, resulting in less respiration taking place and therefore less energy will be released
• 1. During which periods of time did oxygen supply NOT meet oxygen demand?

  Between 3 and 7 seconds

  
• 2. What are the consequences of the oxygen supply not meeting the oxygen demand?

  Lactic acid being produced

  
• 3. Between which points are demand and supply equal?

  Between 7 and 10 seconds

  
• 4. What happens to demand versus supply after exercise stops? What does this mean can happen?

  Demand is significantly lower than what is being delivered. Oxygen is used to help break down lactic acid

  
• Why does the demand for oxygen go from normal to maximum almost immediately after starting exercise (e.g. sprint start in 100m race)?

  Movement has happened straight away (explosive start) therefore oxygen is needed immediately

  
• In the graph below, why does the supply of oxygen only gradually increase?

  The person is respiring

  
• Why is the production of lactic acid at the beginning of physical activity not a good thing?

  Oxygen is used to break down lactic acid rather than aerobically respiring