Practise Response to exercise. 14 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
to supply the muscles with more oxygenated blood / more oxygen (and glucose)
for faster (aerobic) respiration, to transfer more energy for muscle contraction
to remove more carbon dioxide
(c)Answer: Lactic acid
lactic acid
Question 2Medium5 marks
At high altitude, the concentration of oxygen in the air is lower than at sea level. Athletes training at high altitude often notice their heart rate and breathing rate are higher than usual for the same amount of exercise.
(a) Explain why breathing rate and heart rate are higher than usual for the same exercise at high altitude.[2]
(b) Explain why an athlete's muscles might rely more on anaerobic respiration during exercise at high altitude than at sea level.[2]
(c) Suggest one reason why athletes who train at high altitude for several weeks may then perform better at sea level.[1]
Show the answer and mark scheme
(a)
less oxygen is available in each breath of air
the body increases breathing rate and heart rate to try to take in and deliver enough oxygen to the muscles
(b)
even with faster breathing and heart rate, less oxygen reaches the muscles than at sea level
if the muscles cannot get enough oxygen for aerobic respiration alone, they respire anaerobically as well
(c)
the body may adapt by producing more red blood cells / more haemoglobin, so the blood can carry more oxygen to the muscles
the heart and the breathing muscles may become stronger, so more oxygen is delivered to the muscles
Question 3Hard7 marks
A student ran a 5 km race as fast as possible.
(a) Name the organ where lactic acid is converted back into glucose.[1]
(b) Describe and explain the changes that happen in the student's body during and after the race.[6]
Show the answer and mark scheme
(a)Answer: Liver
liver
(b)
heart rate increases, so more blood is pumped to the muscles
breathing rate and breath volume increase, so more oxygen enters the blood and more carbon dioxide is removed
the muscles receive more oxygen and glucose for faster aerobic respiration
if not enough oxygen is supplied, the muscles also respire anaerobically
the incomplete oxidation of glucose causes lactic acid to build up
during long periods of vigorous activity the muscles become fatigued and stop contracting efficiently
after the race, breathing and heart rate stay high for a while (oxygen debt)
blood carries lactic acid to the liver, where it is converted back into glucose
the extra oxygen reacts with / removes the lactic acid
Marked with levels of response: the full level descriptors are in the app.