The diagram below shows part of a muscle myofibril.

Name the protein present in the filaments labelled A and B in the diagram above.

Name the structures labelled C and D in the diagram above.

Describe what happens to the length of the A-band and I-band when the muscle contracts.

Describe the role of calcium ions in muscle contraction.

The diagram below shows a transmission electron micrograph of cardiac muscle.

Name structures X, Y, and Z shown in the diagram above.

Give the name of structure A shown in the diagram above.

Describe the role of ATP in the process of muscle contraction.

Describe the role of tropomyosin in the process of muscle contraction.

The diagram below shows the banding pattern within a single sarcomere.

Label the I-bands, A-band, and the H-zone on the diagram below.

Explain the appearance of the banding pattern shown in the diagram above.

Muscle contraction is explained by the sliding filament theory.

Describe the role of myosin filaments in the sliding filament model of muscle contraction.

Skeletal muscles are made up of slow twitch and fast twitch muscle fibres.

Slow twitch fibres contract slowly and can function for a long time without getting tired.

Fast twitch fibres contract quickly but fatigue very quickly.

Slow twitch fibres are surrounded by more capillaries than fast twitch fibres.

Suggest and explain the advantage of this.

Fast twitch fibres mainly carry out anaerobic respiration. They also contain a higher concentration of glycogen than slow twitch fibres.

Suggest and explain the advantage of this higher glycogen supply.

During intense exercise, the concentration of hydrogen ions increases in muscles, leading to a reduction in pH.

This reduces the ability of calcium ions to stimulate muscle contraction.

Use this information and your own knowledge to explain why.

Movement at a joint is caused by the contraction of antagonistic muscles.

Explain why muscles occur in antagonistic pairs.

Muscle contraction occurs when the muscle fibre membrane, the sarcolemma, is depolarised.

Describe how the arrival of an action potential at a neuromuscular junction causes depolarisation of the sarcolemma.

Myasthenia gravis (MG) is an autoimmune disease that occurs when antibodies bind to the sarcolemma at neuromuscular junctions.

This weakens the contraction of muscles.

Suggest and explain how.

Mestinon is a drug that can be used in the treatment of MG.

It works by inhibiting the enzyme acetylcholinesterase.

Explain how mestinon may help to treat MG.

The diagram below shows part of a myofibril.

Label a sarcomere on the diagram below.

Describe two pieces of evidence that the diagram above shows a contracted myofibril.

A drug called pancuronium is used during operations to stop muscle contraction.

Pancuronium binds to acetylcholine receptors on muscle fibres.

Suggest why pancuronium is able to bind to acetylcholine receptors.

Suggest how pancuronium prevents muscle contraction.

Muscle contraction depends on the activity of several proteins.

Describe the role of the enzyme ATPase during muscle contraction.

What is the role of phosphocreatine, otherwise known as creatine phosphate, during muscle contraction?

Describe the roles of calcium ions and ATP in muscle contraction.

The diagram below shows part of a sarcomere.

Name protein filaments X and Y shown in the diagram above.

Describe how protein filaments X and Y interact to enable the contraction of a myofibril.

McArdle’s disease is a rare muscle disorder that causes muscle cramps, weakness, and fatigue.

This disease occurs when the muscle cells cannot break down glycogen.

Explain why patients with this disease produce less ATP than healthy people.

Suggest why patients with McArdle’s disease cannot maintain strong muscle contraction during exercise.