4 marksRespiration is a reaction that happens in all cells.
(i)
Why do cells need respiration?
(ii)
Cells use aerobic respiration when oxygen is available.
What are the two products of aerobic respiration?
1 ................................
2 ................................
(iii)
Aerobic respiration releases heat energy.
What term describes a reaction that releases heat energy?
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4 marksFermentation involves enzymes breaking down sugar and releasing carbon dioxide gas.
The volume of carbon dioxide released can be used to measure how fast these enzymes are working.
A student investigates if fermentation works faster at 25°C or 30°C.
She measures the volume of carbon dioxide released in 10 minutes.
The diagram shows the apparatus she uses.
Using a Bunsen burner to heat a water bath is one way the student could keep the flask at a constant temperature.
(i)
What other way could be used to keep the flask at a constant temperature?
[1]
(ii)
She chooses to use a Bunsen burner and water bath.
Give one safety precaution she should take.
[1]
(iii)
Explain why using a Bunsen burner and water bath may introduce errors into her results.
[2]
6 marksThe table shows the student’s results.
| Temperature (°C) |
Volume of carbon dioxide gas released in 10 minutes (cm3) |
||||
| Trial 1 | Trial 2 | Trial 3 | Mean | Range | |
| 25 | 23 | 25 | 22 | 23 | 22-25 |
| 30 | 34 | 29 | 33 | ....................... | 29-34 |
(i)
(ii)
(iii)
(iv)
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1 markYeast cells can respire anaerobically.
Complete the word equation for anaerobic respiration in yeast.
glucose ⟶ ...................................... + ......................................
2 marksWrite down two ways in which anaerobic respiration in yeast cells is different from anaerobic respiration in human muscle cells.
1 ..................................................................
2 ...................................................................
6 marksDate fruits contain three different sugars, fructose, glucose and sucrose.
Different strains of yeast can ferment different sugars to produce a fermented product.
Scientists investigate how two different strains of yeast, A and B, ferment sugars inside date fruits.
Look at their results.
(i)
(ii)
Number of times higher = .................................................. [2]
(iii)
[1]
(iv)
Fermented dates are used to supply both fructose and fermented product.
Explain why it would be best to use yeast B to ferment dates to supply both fructose and fermented product.
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