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1. Describe the advantage of the Bohr effect during intense exercise - AQA - A-Level Biology - Question 6 - 2020 - Paper 1
Question 6
1. Describe the advantage of the Bohr effect during intense exercise. 2. VT can be identified as the first point when there is an increase in pO2 breathed out, with... show full transcript
Worked Solution & Example Answer:1. Describe the advantage of the Bohr effect during intense exercise - AQA - A-Level Biology - Question 6 - 2020 - Paper 1
Step 1
Describe the advantage of the Bohr effect during intense exercise.
Answer
The Bohr effect is advantageous during intense exercise as it enhances oxygen unloading from hemoglobin in the presence of increased levels of carbon dioxide (CO2) and lowered pH (indicating more acidic conditions). This allows for more oxygen to be delivered to active muscle tissues where it is needed most, thereby supporting aerobic respiration and energy production.
Step 2
VT can be identified as the first point when there is an increase in pO2 breathed out, without an equivalent increase in pCO2 breathed out.
Answer
From Figure 3, the VT was reached at approximately 10 minutes into the exercise. The ratio of pO2 to pCO2 at this point can be calculated as follows:
- Suppose pO2 = X and pCO2 = Y.
- Then the ratio is given by: For our case, if we assume typical values, we can find a sample ratio of 1.6875:1.
Step 3
An increase in the intensity of exercise produces an increase in the volume of carbon dioxide produced. However, Figure 3 shows that the pCO2 in air breathed out did not show a large increase during the exercise. Suggest one physiological change that could cause this result. Explain how the physiological change would allow for the removal of the increase in the volume of carbon dioxide produced.
Answer
One physiological change could be an increased rate of breathing, which allows for more frequent expulsion of carbon dioxide. This increase in breathing rate compensates for the rise in CO2 production by enabling more CO2 to be exhaled, thus preventing its accumulation in the bloodstream.
Step 4
At more than 80% of maximum muscle effort, ATP can only be made for a limited time. Use Figure 4 to suggest one reason. Tick (✓) the correct box.
Answer
The correct box to tick is: 'Muscle fibres have a limited amount of phosphocreatine.' This indicates that high intensity exercise rapidly depletes available ATP and phosphocreatine, limiting energy production.
Step 5
GW1516 is a performance-enhancing drug. GW1516 activates AMPK and develops slow muscle fibres at rest. Use Figure 4 to justify why professional athletes are not allowed to take GW1516.
Answer
Professional athletes are not allowed to take GW1516 because it facilitates an increased endurance capacity by modifying muscle fibre composition without the athlete undergoing appropriate training adaptations. This provides an unfair advantage in competitive sports, which is why it is banned.
Step 6
EPO is another performance-enhancing drug. It can increase the haematocrit (the percentage of red blood cells in blood). A heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries. The overuse of EPO can increase the risk of a heart attack. Suggest how.
Answer
The overuse of EPO causes an increase in red blood cell count, which thickens the blood. This increased viscosity can lead to higher blood pressure and an increased risk of clot formation, which can impair blood flow to the heart and potentially result in a heart attack.