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Read the following passage - AQA - A-Level Biology - Question 10 - 2023 - Paper 2
Question 10
Read the following passage. ATP is essential for muscle contraction. The concentration of ATP in skeletal muscle is approximately 5 x 10^-3 mmol g^-1. During maximu... show full transcript
Worked Solution & Example Answer:Read the following passage - AQA - A-Level Biology - Question 10 - 2023 - Paper 2
Step 1
Describe the roles of ATP in muscle contraction.
Answer
ATP plays a crucial role in muscle contraction by providing the energy necessary for several processes:
- Actin-Myosin Interaction: ATP is essential for breaking the actin-myosin bridges during the contraction cycle, allowing myosin heads to detach from the actin filaments, which is critical for muscle relaxation and reattachment.
- Movement of Myosin Head: The energy released from ATP hydrolysis is used to reposition the myosin head, enabling it to 'pull' the actin filaments inward during contraction.
- Calcium Ion Transport: ATP facilitates the active transport of calcium ions back into the sarcoplasmic reticulum, which is vital for muscle relaxation.
Step 2
Calculate how long maximum exercise would last if ATP was not resynthesised.
Answer
If ATP is utilized at a rate of approximately 3.7 mmol kg^-1 s^-1 and the concentration of ATP in skeletal muscle is 5 x 10^-3 mmol g^-1, we first convert this concentration to kg:
- Concentration in kg:
5 x 10^-3 mmol g^-1 = 5 x 10^-3 mmol/kg (assuming 1 kg of muscle)
To find the duration without resynthesis:
ext{Time (s)} = rac{ ext{Total ATP}}{ ext{ATP usage rate}} = rac{5 x 10^{-3} ext{ mmol}}{3.7 ext{ mmol/s}} \\
ext{Time (s)}
ightarrow 1.35 ext{ seconds}
Thus, maximum exercise would last approximately 1.35 seconds.
Step 3
Describe and explain how taking creatine supplements and 'carbohydrate loading' can improve performance of different types of muscle fibres during different types of exercise.
Answer
Creatine supplements primarily benefit fast-twitch muscle fibers used during intense, short-duration exercises like sprinting. Creatine aids in the formation of phosphocreatine, which can quickly regenerate ATP, enhancing the ability of muscles to perform high-intensity activities.
On the other hand, 'carbohydrate loading' is more beneficial for slow-twitch fibers, which are predominantly engaged during longer, endurance-type exercises such as marathons. By storing more glycogen, muscle endurance improves, allowing athletes to sustain prolonged activity without fatigue.
Step 4
Suggest and explain how GLUT4 and CD36 transport proteins are beneficial during exercise.
Answer
GLUT4 transport proteins increase glucose uptake into muscle cells during exercise, which is crucial for providing energy, particularly during high-intensity activities. Increased GLUT4 translocation to the cell membrane enhances the efficiency of glucose utilization as a fuel source.
Similarly, CD36 transport proteins facilitate the uptake of fatty acids into mitochondria where they are oxidized for energy production. This is especially useful during prolonged exercises when the body relies more on lipid metabolism as an energy source.
Step 5
An increase in muscle activity causes an increase in heart rate. Describe and explain how.
Answer
An increase in muscle activity leads to a rise in carbon dioxide levels in the blood. This change is detected by chemoreceptors that send more nerve impulses to the cardiac control center.
These impulses result in an increase in heart rate to pump more blood, and therefore more oxygen, to the working muscles. Additionally, the heart rate responds to the need for enhanced removal of carbon dioxide, maintaining homeostasis and ensuring efficient metabolic function during physical activity.