Overview of respiration and glycolysisEdexcel International A Level Biology: Subtopic test

1. 1
   Glycolysis is the first stage of respiration in a liver cell supplied with glucose. In the later reactions of glycolysis a total of four molecules of ATP are made from each molecule of glucose.

   (a)

   Where in the cell does glycolysis take place?

   [1 mark]

   • AIn the matrix of the mitochondrion
   • BOn the inner membrane of the mitochondrion
   • CIn the nucleus
   • DIn the cytoplasm

   (b)

   What are the products of glycolysis, in addition to ATP, from one molecule of glucose?

   [1 mark]

   • AOne pyruvate and one reduced NAD
   • BTwo pyruvate and two reduced NAD
   • CTwo pyruvate and four reduced NAD
   • DFour pyruvate and two reduced NAD

   (c)

   Explain why the net gain of ATP from glycolysis is two molecules per molecule of glucose.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student investigates respiration in yeast. She adds yeast suspension to glucose solution containing methylene blue, a redox indicator that is blue when oxidised and colourless when reduced. Each tube is covered with a thin layer of oil and kept in a water bath, and she records the time taken for the blue colour to disappear. One tube is kept at 15 °C and another at 35 °C.

   (a)

   Why does the methylene blue become colourless?

   [1 mark]

   • AIt is oxidised by oxygen dissolved in the solution
   • BIt is broken down by enzymes released from the yeast
   • CIt accepts hydrogen released in respiration and becomes reduced
   • DIt is used up as a respiratory substrate

   (b)

   Which control would best show that the colour change is caused by enzymes in living yeast?

   [1 mark]

   • ABoiled and cooled yeast, with glucose and methylene blue
   • BLiving yeast and methylene blue at a different temperature
   • CMethylene blue in water only
   • DLiving yeast with a doubled concentration of glucose

   (c)

   Explain why the methylene blue becomes colourless more quickly at 35 °C than at 15 °C.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   During a 100 m sprint, the muscle fibres in an athlete's leg respire anaerobically. In one fibre, 0.50 mmol of glucose is respired anaerobically by glycolysis alone.

   (a)

   Calculate the amount of lactate and the net amount of ATP produced from the glucose in this fibre.

   [3 marks]

   (b)

   After the race the athlete continues to breathe heavily. Describe what happens to the lactate and explain why the high breathing rate continues.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In a steady jog, an athlete's muscle cells respire aerobically. During the final sprint, the oxygen supply cannot keep up with the demand and the cells rely on anaerobic respiration. A student asks why cells release the energy from glucose in a long series of enzyme-controlled steps, and not in one step as happens when glucose is burned in a flame.

   (a)

   Explain why respiration is a stepped process catalysed by enzymes, and describe the overall reaction of aerobic respiration.

   [6 marks]

   (b)

   Compare the roles of glycolysis in aerobic and anaerobic respiration, and explain why glycolysis can continue during the sprint.

   [6 marks]

   Total for question 4: 12 marks

End of questions