Skeletal muscle and movementEdexcel International A Level Biology: Flashcards

Exam questions on Skeletal muscle and movement

1. A physiotherapist is demonstrating how the human arm moves at the elbow joint. The biceps muscle on the front of the upper arm and the triceps muscle on the back of the upper arm both attach, by tendons, to the bones of the lower arm. The bones of the upper and lower arm are held together at the elbow by ligaments.
   Explain how the biceps and triceps interact with the bones of the arm to extend (straighten) the elbow.2 marks
2. A student prepares a thin longitudinal section of mammalian skeletal muscle and examines a single muscle fibre with an electron microscope. The fibre is long and cylindrical, contains many nuclei, and is packed with parallel bundles of protein filaments that show a regular pattern of light and dark bands.
   The muscle fibre contains many mitochondria lying close to the myofibrils. Explain the advantage of this.2 marks
3. A sports scientist takes small muscle samples (biopsies) from the thigh of two athletes, a marathon runner and a 100 m sprinter, and examines the fibres. Sample X: dark red fibres with a very high density of mitochondria, a high concentration of myoglobin and a dense network of capillaries; low stores of glycogen. Sample Y: pale fibres with few mitochondria, little myoglobin, a sparse capillary network, high stores of glycogen and phosphocreatine, thicker myosin filaments and a high ATPase activity.
   Deduce which sample came from the sprinter. Explain your answer using the data.3 marks