6- Muscles =)

Question 1

The scientists then compared the length of time that the control mice and the trained mice could carry out prolonged exercise. The trained mice were able to
exercise for a longer time period than control mice.
Explain why. (3)

Answer 1

• ↑ aerobic resp –> ↑ ATP
• anaerobic resp delayed
• ↓ lactate

Question 2

Describe the role of phosphocreatine (PC) in providing energy during muscle contraction. (2)

Answer 2

• provides Pi
• to make ATP

quick, short bursts

ADP + PCr –> ATP + Cr

Question 3

Glycogen granules are present in skeletal muscle.
Explain their role in skeletal muscle. (2)

Answer 3

• hydrolysed into glucose
• for resp. –> ATP

Question 4

Describe the roles of ATP in muscle contraction. (2)

Answer 4

1. myosin head to bend
2. actin filament to move
3. breaking actin-myosin crossbridge
4. a.t. of Ca2+ ions into sarcoplasmic reticulum

Question 5

Both slow and fact muscle fibres contain ATPase.
Explain why. (2)

Answer 5

• for ATP hydrolysis
• ATP required for contraction
• used by myosin

ATPase = ATP hydrolase

Question 6

Namethe molecule that attaches to Z line at the end of a sarcomere. (1)

Answer 6

actin

Question 7

Name the molecule that breaks down ATP. (1)

Answer 7

ATPase

Question 8

Namethe molecule that covers binding site on actin in relaxed myofibril. (1)

Answer 8

tropomyosin

Question 9

One form of muscle disease is caused by a mutated allele of a gene. This leads to production of myosin molecules that are unable to bind to other myosin molecules.
If myosin molecules are unable to bind to other myosin molecules, this prevents muscle contraction.
Use the diagram and your knowledge of how muscles contract to suggest why. (3)

Answer 9

• x form myosin filaments
• x pull actin
• myosin moves
• x move actin towards each other (x shorten sarcomere)