exam

Question 1

What is the role of ATP in muscle contraction?

Answer 1

• Attachment of new ATP molecules to each myosin head causes myosin to detach from the actin site
• Hydrolysis of ATP on myosin head causes the myosin head to bend which pulls actin molecules.

Question 2

What is the role of calcium ions in muscle contraction?

Answer 2

• Calcium ions diffuse into myofibrils from the sarcoplasmic reticulum. This causes movement of tropomyosin on actin with exposes the binding sites on the actin.

Question 3

What is the role of actin in muscle contraction?

Answer 3

• Calcium ions released from the sarcoplasmic reticulum will bind to troponin which causes tropomyosin to move and expose the binding sites on actin where myosin heads will bind to form cross bridges

Question 4

What is a power stroke?

Answer 4

When the myosin head pulls the actin towards the M-line

Question 5

What is the role of myosin in muscle contraction?

Answer 5

• Myosin heads bind to the exposed binding sites on the actin to form cross bridges. ADP and Pi are released during this which triggers the power stroke

Question 6

What is the role of phosphocreatine in muscle contraction.

Answer 6

• Acts as a energy reserve to quickly regenerate ATP in the absence of oxygen or high demand in ATP. PCr will donate a phosphate to ADP to from ATP and creatine

Question 7

What are the structure, location and general properties of slow muscles?

Answer 7

Structure - red due to myoglobin, many mitochondria for aerobic respiration, fewer myosin filaments

Location - found in muscles involved in posture and endurance activities e.g. back and legs

Properties - suitable for endurance activities e.g. long distance running, contract slowly but are fatigue resistant, produce less powerful contractions, specialise in aerobic respiration for ATP production

Question 8

What are the structure, location and general properties of slow muscles?

Answer 8

Structure - white colour due to less myoglobin, fewer mitochondria but more myosin filaments and greater conc. of glycogen and phosphocreatine

Location - found in muscles involved in rapid intense activity e.g. arms and legs for sprinting or running

Properties - suitable for intense activity e.g. weightlifting, contract rapidly and powerfully but fatugue quicjly.