Aerobic respirationIB MYP Biology: Subtopic test

1. 1
   During a marathon in Nairobi, a runner's leg muscles release energy by aerobic respiration. As the race goes on, her breathing rate and heart rate both rise.

   (a)

   In which part of the runner's muscle cells does aerobic respiration take place?

   [1 mark]

   • AThe nucleus
   • BThe mitochondria
   • CThe chloroplasts
   • DThe ribosomes

   (b)

   Which pair of substances are the reactants in aerobic respiration?

   [1 mark]

   • AGlucose and carbon dioxide
   • BOxygen and water
   • CCarbon dioxide and water
   • DGlucose and oxygen

   (c)

   Explain why the runner's breathing rate increases during the race.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hummingbird in Costa Rica beats its wings about 50 times every second and keeps its body at around 40 °C. It feeds on sugar-rich nectar, and its flight muscle cells contain a very large number of mitochondria.

   (a)

   Which activity in the hummingbird directly uses energy released by respiration?

   [1 mark]

   • AContraction of the wing muscles
   • BDiffusion of oxygen into the blood
   • CEvaporation of water from the body surface
   • DPhotosynthesis in the plants it visits

   (b)

   Which statement about respiration is correct?

   [1 mark]

   • AIt happens only in muscle cells
   • BIt happens only in the dark
   • CIt happens in all living cells
   • DIt creates energy from nothing

   (c)

   Explain why the hummingbird's flight muscle cells need a very large number of mitochondria.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student wants to show that living seeds release energy. She puts 100 g of germinating pea seeds in one vacuum flask and 100 g of boiled (dead) pea seeds in a second flask of the same size. Each flask has a thermometer in a cotton-wool stopper. Both start at 20.0 °C. After 24 hours the flask of germinating peas reads 27.0 °C and the flask of boiled peas reads 20.5 °C.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Explain the results and suggest one way to improve the reliability of the investigation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A city in the Gulf, where summer temperatures often reach 45 °C, plans a network of shaded cycle lanes and a public bike-hire scheme to persuade residents to cycle to work instead of driving.

   (a)

   Explain how a cyclist's leg muscle cells obtain the energy they need for pedalling, and why the cyclist's breathing rate and heart rate rise.

   [6 marks]

   (b)

   Discuss and evaluate whether the city should spend public money on the cycle network.

   [6 marks]

   Total for question 4: 12 marks

End of questions