>\n- This energy is released by an increased rate of (aerobic) respiration B1\n- Higher cardiac output increases the rate of blood flow, delivering more oxygen and glucose to the working muscle cells B1\n- It also ensures that carbon dioxide (a waste product of respiration) is removed from the muscle tissue more rapidly B1","marks":4,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"linking_respiration_to_cardiac_output","label":"Linking respiration to cardiac output","steps":[{"type":"text","order":0,"title":"Identify the demand","content":"When the athlete starts sprinting, their muscles contract more frequently and more forcefully than when walking. This higher rate of muscle contraction needs more energy. **This earns the first mark.**","highlights":[{"text":"transition from walking to sprinting","location":"specification"}]},{"type":"text","order":1,"title":"Link energy to respiration","content":"Muscle cells release this extra energy by increasing the rate of **aerobic respiration**. Aerobic respiration uses oxygen to release energy from glucose. This clear link from greater activity to greater respiration earns the second mark.","highlights":[{"text":"Explain why an athlete's cardiac output must increase","location":"specification"}]},{"type":"text","order":2,"title":"Explain faster delivery","content":"Cardiac output is the volume of blood pumped by the heart each minute. Increasing it increases the rate of blood flow to the working muscles, delivering more oxygen and glucose for the increased aerobic respiration. This earns a further mark.","highlights":[{"text":"cardiac output must increase","location":"specification"}]},{"type":"text","order":3,"title":"Include waste removal","content":"Finally, faster blood flow removes carbon dioxide from the muscle tissue more rapidly. Carbon dioxide is a waste product of respiration, so this prevents it building up as the muscles work harder. This completes the final mark.","highlights":[{"text":"Explain why an athlete's cardiac output must increase","location":"specification"}]}]}],"generatedAt":"2026-07-21T05:06:58.301Z","modelVersion":"gpt-5.6-terra","explanationVersion":"v3"},"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"23b21e89-6dde-496f-bd15-c5365ef8395d","revisionId":"ac8d34b2-6071-4baf-9992-12dbb266d900","questionNumber":null,"questionType":"LA","specification":"","difficulty":3,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"a85475ee-3733-4ea6-9924-737327da0b85","label":null,"content":"Table 2 shows the results of an investigation into how two different types of physical activity affect breathing rate over a 16-minute period.\n\n### Table 2\n\n| Type of exercise | Breathing rate (breaths per minute) | | | | |\n| :--- | :---: | :---: | :---: | :---: | :---: |\n| | **0 minutes** | **4 minutes** | **8 minutes** | **12 minutes** | **16 minutes** |\n| High-intensity cycling | 12 | 28 | 36 | 42 | 42 |\n| Gentle stretching | 12 | 14 | 13 | 14 | 12 |\n\nComment on the differences in the breathing rates during these two types of exercise.","markscheme":"- States that high-intensity cycling results in a much greater overall increase in breathing rate compared to gentle stretching, OR that stretching has a minimal/very small effect on breathing rate B1\n- Compares trends/data: states that cycling breathing rate increases steadily from $12$ breaths per minute and plateaus at $42$ breaths per minute, while stretching breathing rate stays low, peaking at only $14$ breaths per minute (or fluctuating between $12$ and $14$ breaths per minute) B1\n- Compares start and end points: notes that while both exercises start at the same baseline of $12$ breaths per minute, by $16$ minutes cycling remains highly elevated at $42$ breaths per minute whereas stretching has returned to the initial baseline of $12$ breaths per minute B1","marks":3,"order":0,"markingRubric":null,"explanation":{"methods":[{"i

Blood, the heart, circulation and respiration

Question 5

Blood, the heart, circulation and respiration Questions

Blood, the heart, circulation and respiration

Question 5

Blood, the heart, circulation and respiration Questions