O-LevelBiologyTransport in Humans5090/21 · May/June 2022 · Q214 Marks

A man decides to do some fitness training to improve his ability to provide oxygen to his muscles.

(a)(i)Describe the route an oxygen molecule takes from the atmosphere to reach the muscles.[4]
(a)(ii)The fitness training is designed to result in changes to the man's body. Suggest two body changes that would improve his ability to provide oxygen to his muscles. 1 2[2]
(b)(i)State the name of the chemical process that uses oxygen to release energy in the muscles.[2]
(b)(ii)Use the graph to determine the maximum volume of oxygen the man consumes in one minute.[1]
(b)(iii)The graph shows that it is possible for the man to increase the intensity of his exercise beyond the point at which he has reached his maximum oxygen consumption. He can only do this for a short period of time. Explain why.[3]
(b)(iv)After four weeks of fitness training the man measures his oxygen consumption again. On the graph, sketch a line to show the expected results of successful fitness training.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[2] lungs: enters via nose / nasal passages + into larynx/trachea; travels through bronchus / bronchi / bronchioles ; to air sacs / alveoli;
[2] circulation: diffuses + into blood / into capillaries / from blood to muscle; red blood cells / haemoglobin ; transported by pulmonary vein ; pumped by heart ; through arteries / arterioles ;
[2] any two from: a larger lung capacity / stronger intercostal muscles ; stronger / thicker + cardiac / ventricle muscle ; cardiac muscle able to pump more blood in each cardiac cycle ; improved blood supply to heart muscle ; more haemoglobin / red blood cells ;
[1] aerobic;
[1] respiration;
[1] 3.4 + dm³;
[3] any three from: respire anaerobically ; without oxygen / lack of oxygen ; respiration + energy released ; lactic acid; lactic acid builds up in / affects + muscles ;
[1] line starts close to rest point line on y axis + continues upwards on same straight line as before training ;
[1] maximum oxygen consumption is higher + reached at higher exercise intensity;

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