Muscles and Movement

Question 1

Describe changes caused when calcium ions bind to the molecules shown. (2)

Answer 1

• tropomyosin is moved
• myosin binding site is exposed

Question 2

Explain how calcium ion binding to molecules causes muscles to contract. (4)

Answer 2

• myosin head binds to binding site

^ changes shape

• actin filament slide over myosin

^ therefore, sarcomeres shorten

Question 3

Describe role of calcium ions in muscle fibre contractions. (3)

Answer 3

• Ca ions bind to troponin

^ causing tropomyosin to be displaced

• exposing myosin binding sites

Question 4

Explain how extensor and flexor muscles bring about movement to the lower leg. (2)

Answer 4

• tendons attach muscle to bone
• flexor and extensor work as an antagonistic pair

Question 5

Describe 2 structural differences between fast and slow twitch muscle fibres. (2)

Answer 5

• fast twich has no mitochondria , slow twitch has many
• fast twitch has no capillaries , slow has many

Question 6

Explain how muscle fibre structure is related to its specialised function. (3)

Answer 6

• many mitochondria for respiration
• have myofibrils

^ allow muscle contraction

Question 7

Describe how the tertiary structure of myosin is related to its function. (2)

Answer 7

• globular head can bind to actin
• has ATP binding site