The diagram shows the percentage of oxygen in a sealed chamber containing germinating barley seeds. A sensor recorded the oxygen percentage during a 30 minu...
Question 1 Report
The diagram shows the percentage of oxygen in a sealed chamber containing germinating barley seeds. A sensor recorded the oxygen percentage during a 30 minute investigation. The barley was supplied with water but no extra food.
(a) Name the type of respiration taking place in the barley seeds. [1]
(b) Calculate the decrease in oxygen percentage after 30 minutes. [2]
(c) Explain the change in oxygen percentage shown by the diagram. [3]
(d) Describe two changes that would make the investigation a fair comparison of the respiration rates of barley at different temperatures. [2]
(e) Complete the word equation for the process that releases energy in the barley cells. [3]
Answer Details
(a) The germinating barley seeds are carrying out aerobic respiration. [1]
(b) \[21.0\% - 16.5\%=4.5\] The oxygen percentage decreases by 4.5 percentage points. [2]
(c) Barley seed cells use oxygen for aerobic respiration. Respiration releases energy from stored food, such as glucose, and this energy supports germination. As oxygen is used in the sealed chamber, its percentage falls. [3]
(d) Use the same mass or number of barley seeds at each temperature, and use the same time period or chamber volume. This controls factors other than temperature, making the comparison fair. [2]
(e) \[\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy released}\] [3]
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