Respiratory quotient and the amphibolic pathway — practice questions

Question 1 · difficulty L1 · recall

What is the respiratory quotient when carbohydrate is completely oxidised aerobically?

• A. 1.0
• B. 0.7
• C. Greater than 1 only
• D. 0

Question 2 · difficulty L2 · understanding

Why is the respiratory pathway described as amphibolic?

• A. It functions only during anaerobic respiration
• B. It participates in both breakdown and biosynthetic pathways
• C. It occurs only in amphibians
• D. It produces only catabolic end products

Question 3 · difficulty L2 · understanding

Why is the respiratory quotient for fats usually less than 1?

• A. They consume no oxygen
• B. They release no carbon dioxide
• C. Their oxidation consumes proportionally more oxygen than the carbon dioxide released
• D. They contain no carbon

Question 4 · difficulty L3 · understanding

$$2\left(\mathrm{C}_{51} \mathrm{H}_{98} \mathrm{C}_6\right)+145 \mathrm{O}_2 \rightarrow 102 \mathrm{CO}_2+98 \mathrm{H}_2 \mathrm{O}+\text { energy }$$ The Respiratory Quotient (RQ) of a biomolecule used for respiration, as per the above equation would be :

• A. Between 0.5 and 0.95
• B. Less than 0.5
• C. 1.0
• D. Between 1.25 and 2

Question 5 · difficulty L3 · understanding

Fatty acids are connected with the respiratory pathway through :

• A. Acetyl CoA
• B. $$\alpha$$-Ketoglutaric acid
• C. Dihydroxy acetone phosphate
• D. Pyruvic acid

Question 6 · difficulty L3 · application

A germinating seed shows an RQ close to 0.7. Which stored respiratory substrate is most likely being used predominantly?

• A. Pure glucose only
• B. Carbohydrate
• C. Organic acid
• D. Fat

Question 7 · difficulty L4 · analysis

An intermediate of the Krebs cycle is withdrawn to synthesise an amino acid, while amino-acid carbon skeletons can also be converted into respiratory intermediates. What does this most directly illustrate?

• A. The amphibolic nature of respiration
• B. Fermentation
• C. Photophosphorylation
• D. Only substrate-level phosphorylation