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a) Complete the sentence by putting a cross (✖) in the box next to your answer - Edexcel - GCSE Biology - Question 2 - 2017 - Paper 1
Question 2
a) Complete the sentence by putting a cross (✖) in the box next to your answer. The blood vessel that transports oxygenated blood from the heart is the: ☐ A aorta ... show full transcript
Worked Solution & Example Answer:a) Complete the sentence by putting a cross (✖) in the box next to your answer - Edexcel - GCSE Biology - Question 2 - 2017 - Paper 1
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b) Explain how the concentration gradient is maintained between the blood and muscles.
Answer
The concentration gradient is maintained through continuous cellular respiration in the muscles, which consumes oxygen and produces carbon dioxide. This process ensures that oxygen levels in the blood remain higher than in the muscle cells, prompting oxygen diffusion from the blood into the muscles. As oxygen diffuses into the muscles, the concentration in the blood decreases while the muscles are constantly replenished by fresh oxygen-rich blood.
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c) (i) Describe the relationship between cardiac output and running speed.
Answer
As running speed increases, cardiac output increases. The relationship is linear up to speeds of about 12-16 km/h, after which it increases more slowly. This means that at lower running speeds, even small increases in speed can lead to proportional increases in cardiac output.
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c) (ii) Explain why this runner gets muscle cramp when he runs at speeds over 24 km per hour.
Answer
The runner experiences muscle cramps at high speeds due to a combination of factors, including an increased demand for oxygen that can lead to anaerobic respiration when oxygen supply is insufficient. This process results in the accumulation of lactic acid in the muscles, which can cause fatigue and cramping. Additionally, at high speeds, the demand for blood circulation increases, and the muscles may not receive enough oxygen to meet their metabolic needs.