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| Respiratory Quotient |
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| During aerobic respiration oxygen is consumed and carbon dioxide is evolved. |
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| The ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time is called respiratory quotient (RQ). |
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| RQ is determined with the help of an apparatus called respirometer. |
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| The RQ depends upon the type of respiratory substrate used during respiration. It is different for different substrates. |
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| Carbohydrates |
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| The value of RQ is equal to 1 if carbohydrates are the respiratory substrates in aerobic respiration. |
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| Fats |
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| When the respiratory substrate is fat, the RQ is about 0.7. |
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| Example: Tripalmitin |
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| Fats contain less oxygen than carbohydrates and so they require more oxygen for oxidation. |
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| Organic acids |
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| When organic acids are broken down as respiratory substrates under aerobic conditions the RQ is more than one. Organic acids contain more oxygen than carbohydrates and therefore require less oxygen for their oxidation. |
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| Examples: |
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| Anaerobic respiration |
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| The value of RQ is infinity during anaerobic respiration because CO2 is produced but O2 is not utilised. |
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