Muscles, skeleton and movementEdexcel A-Level Biology A: Subtopic test

1. 1
   A physiotherapist is assessing a patient who is recovering from an elbow injury. She asks the patient to bend the arm at the elbow and then straighten it again, and observes which muscles of the upper arm are working. She is also checking the tissues that hold the joint stable.

   (a)

   Which structure attaches a skeletal muscle to a bone?

   [1 mark]

   • ALigament
   • BCartilage
   • CTendon
   • DSynovial membrane

   (b)

   When the patient straightens the arm, which row correctly describes the muscles of the upper arm?

   [1 mark]

   • ABiceps and triceps both contract
   • BBiceps contracts and triceps relaxes
   • CBiceps and triceps both relax
   • DBiceps relaxes and triceps contracts

   (c)

   Explain why skeletal muscles are arranged in antagonistic pairs.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A sports scientist takes small samples of thigh muscle from a marathon runner and a sprinter. Sample X has many mitochondria, a high concentration of myoglobin and a dense network of capillaries. Sample Y has fewer mitochondria, thicker myosin filaments, large stores of phosphocreatine and glycogen, and a high activity of glycolytic enzymes.

   (a)

   Which of the following correctly identifies the sample from the marathon runner and the reason?

   [1 mark]

   • AY, because phosphocreatine provides ATP rapidly for long events
   • BX, because many mitochondria allow sustained aerobic respiration
   • CY, because fast twitch fibres resist fatigue
   • DX, because it has thicker myosin filaments

   (b)

   Why is a high concentration of myoglobin an advantage in slow twitch fibres?

   [1 mark]

   • AIt stores oxygen for aerobic respiration
   • BIt stores glycogen for glycolysis
   • CIt makes the fibre contract faster
   • DIt removes lactate from the fibre

   (c)

   Explain why the fibres in sample Y can contract rapidly but fatigue quickly.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Skeletal muscle fibres are long cells formed by the fusion of many cells, so each fibre contains many nuclei. The fibre is surrounded by a cell surface membrane called the sarcolemma and is packed with myofibrils. The sarcolemma folds inwards at intervals to form T-tubules, and a network of membrane called the sarcoplasmic reticulum lies around the myofibrils.

   (a)

   Describe how a myofibril is organised into sarcomeres.

   [3 marks]

   (b)

   Explain how the structure of a skeletal muscle fibre adapts it for rapid, strong contraction.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A sports scientist compares the thigh muscles of a 100 m sprinter and a long-distance cyclist. Biopsies show that about 75% of the sprinter's fibres are fast twitch, while about 80% of the cyclist's fibres are slow twitch. The cyclist's legs repeatedly extend and bend at the knee as she turns the pedals.

   (a)

   Compare the structure and physiology of fast twitch and slow twitch muscle fibres, and explain how this suits the sprinter and the cyclist.

   [6 marks]

   (b)

   Explain how the muscles, tendons, skeleton and ligaments interact at the knee to enable the cyclist's leg to extend and then bend.

   [6 marks]

   Total for question 4: 12 marks

End of questions