Question 1

Multiple choiceMedium1 mark

The diagrams show energy transfers per 100 kJ of chemical energy entering cell respiration in representative autotrophic and heterotrophic cells. Which statement gives the total heat released in each cell type and the stages at which it is released?

Autotrophic cell60 kJ transferred inATP100 kJchemical energyinputCell respirationATP used in cellsCell work:35 kJHeat to environment:40 kJHeat to environment:25 kJHeterotrophic cell70 kJ transferred inATP100 kJchemical energyinputCell respirationATP used in cellsCell work:50 kJHeat to environment:30 kJHeat to environment:20 kJ
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Answer: D. Heat is released at both stages shown, so add the heat outputs for each cell type: autotrophic cells, 40 + 25 = 65 kJ; heterotrophic cells, 30 + 20 = 50 kJ per 100 kJ input.

A: counts only the heat released during cell respiration. B: counts only the heat released when ATP is used. C: gives the totals but reverses the cell-type labels.

Remember: energy transfers are not 100% efficient, including when ATP is produced and when it is used.

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