Run for your lifeEdexcel A-Level Biology A: Topic test

1. 1
   A cyclist pedals up a long hill. The muscles at the front and the back of her thigh act as an antagonistic pair to straighten and bend her knee.

   (a)

   Which row correctly describes the muscles when her knee is straightened?

   [1 mark]

   • ABoth muscles contract equally
   • BThe quadriceps (extensor) contracts while the hamstring (flexor) relaxes
   • CThe hamstring (extensor) contracts while the quadriceps (flexor) relaxes
   • DThe quadriceps contracts and pulls on a ligament that moves the lower leg

   (b)

   Which event allows myosin heads to bind to actin in a contracting muscle fibre?

   [1 mark]

   • ATroponin hydrolyses ATP, releasing energy to expose the binding sites
   • BCalcium ions bind to myosin, which activates its binding site
   • CATP binds to actin and moves tropomyosin out of the way
   • DCalcium ions bind to troponin, which moves tropomyosin and exposes the binding sites on actin

   (c)

   Explain the role of ATP in the cross-bridge cycle in the muscle fibres.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A sprinter and a marathon runner both depend on respiration to supply ATP to their muscles, but they use different mixtures of pathways during a race.

   (a)

   Which row lists the products of the Krebs cycle?

   [1 mark]

   • ACarbon dioxide, reduced NAD, reduced FAD and ATP
   • BLactate, reduced NAD and ATP
   • CPyruvate, carbon dioxide and water
   • DWater, ATP and carbon dioxide

   (b)

   What is the final electron acceptor in the electron transport chain of the mitochondrion?

   [1 mark]

   • APyruvate
   • BNAD
   • COxygen
   • DCarbon dioxide

   (c)

   Explain why the sprinter's muscle cells convert pyruvate to lactate when oxygen is in short supply.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A sports scientist studies the heart of an endurance athlete. At rest her heart rate is 60 beats per minute and her stroke volume is 75 cm³. During hard exercise her heart rate rises to 165 beats per minute and her cardiac output rises to 24 dm³ min⁻¹.

   (a)

   Calculate the athlete's cardiac output at rest in dm³ min⁻¹, and her stroke volume during hard exercise in cm³. Show your working.

   [3 marks]

   (b)

   Use the figures to explain how her cardiac output increases during exercise, and how this helps her muscles.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A rower competes in a 2000 m race lasting about 6.5 minutes. Her thigh muscles contain a high proportion of slow twitch fibres, but also many fast twitch fibres that she uses in the sprint finish.

   (a)

   Explain how the products of glycolysis, the link reaction and the Krebs cycle are used to make ATP by oxidative phosphorylation in the rower's muscle cells.

   [6 marks]

   (b)

   Explain how slow twitch and fast twitch muscle fibres each contribute to her performance in the race.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   Cortisol is a steroid hormone released during prolonged exercise. Its concentration in the blood is controlled by negative feedback, and it alters the transcription of genes in its target cells.

   (a)

   Which statement describes negative feedback control of blood cortisol concentration?

   [1 mark]

   • AA rise in cortisol concentration triggers responses that increase its release further
   • BThe cortisol concentration stays exactly the same at all times
   • CA rise in cortisol concentration triggers responses that reduce its release, returning it towards the normal level
   • DThe effector detects the change and then signals the receptor to respond

   (b)

   Which statement describes how cortisol alters gene expression?

   [1 mark]

   • AIt binds to an intracellular receptor, and the hormone-receptor complex acts as a transcription factor that binds to DNA and switches a gene on or off
   • BIt binds directly to RNA polymerase in the cytoplasm
   • CIt is translated into a protein that is a transcription factor
   • DIt changes the base sequence of the gene by mutation

   (c)

   Explain why cortisol, a lipid-soluble steroid, can alter transcription directly, whereas adrenaline, a water-soluble hormone, cannot.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   The heart of a healthy person beats about 100 000 times each day. Each beat is started and coordinated by electrical activity within the cardiac muscle itself.

   (a)

   Which sequence shows the correct pathway of the wave of excitation through the heart?

   [1 mark]

   • AAtrioventricular node, sinoatrial node, bundle of His, Purkyne fibres, atrial walls
   • BSinoatrial node, Purkyne fibres, bundle of His, atrioventricular node, atrial walls
   • CSinoatrial node, atrioventricular node, Purkyne fibres, bundle of His, ventricular walls
   • DSinoatrial node, atrial walls, atrioventricular node, bundle of His, Purkyne fibres

   (b)

   What is the main function of the short delay in the transmission of excitation at the atrioventricular node?

   [1 mark]

   • AIt allows the ventricles to contract before the atria
   • BIt allows the atria to finish contracting and the ventricles to fill with blood before the ventricles contract
   • CIt prevents the sinoatrial node from firing too often
   • DIt allows the blood to be oxygenated before it leaves the heart

   (c)

   Explain why the Purkyne fibres carry the wave of excitation to the base of the ventricles, rather than the wave spreading directly down through the ventricle walls from the atria.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A ten-year study compared 8000 adults who took very little exercise with 8000 adults who exercised regularly. In the first group 480 people developed type 2 diabetes, and in the second group 160 people developed it. The two groups were not matched for diet or body mass.

   (a)

   Calculate the percentage of each group that developed type 2 diabetes, and how many times greater the percentage is in the group who took very little exercise.

   [3 marks]

   (b)

   A student concludes that taking too little exercise causes type 2 diabetes. Give two reasons why this conclusion may not be justified, and state two possible disadvantages of exercising too much.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A professional cyclist's blood is monitored in a laboratory while she cycles at increasing intensity. Her team is also discussing whether she should use the hormone erythropoietin (EPO), which increases red blood cell production and the oxygen-carrying capacity of the blood. EPO is banned by sports federations.

   (a)

   Explain how her body detects and responds to the increasing demand for oxygen, and the need to remove carbon dioxide, as the intensity of exercise increases.

   [6 marks]

   (b)

   Discuss the ethical arguments for and against allowing athletes to use EPO.

   [6 marks]

   Total for question 8: 12 marks

End of questions