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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 critical role in muscle contraction by providing energy for the following processes:
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Breaking Actin-Myosin Bridges: ATP is necessary to break the bonds formed between actin and myosin during contraction, allowing the myosin head to detach from actin.
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Moving Myosin Head: The hydrolysis of ATP changes the shape of the myosin head. This action enables the myosin to pull the actin filaments inward, contributing to muscle shortening and contraction.
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Active Transport of Calcium Ions: ATP is essential for transporting calcium ions back into the sarcoplasmic reticulum, which is crucial for muscle relaxation.
Step 2
Calculate how long maximum exercise would last if ATP was not resynthesised.
Answer
Maximum exercise would last approximately 1.35 seconds if ATP was not resynthesised. This is calculated using the rate of ATP usage of 3.7 mmol kg^-1 s^-1 and the initial ATP concentration of 5 x 10^-3 mmol g^-1.
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
Taking creatine supplements and 'carbohydrate loading' can enhance muscle performance through the following mechanisms:
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Creatine Supplementation: Creatine increases phosphocreatine levels in muscles, providing additional energy during intense, short-term exercises such as sprinting. This allows fast-twitch muscle fibres to perform better due to the rapid availability of ATP.
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Carbohydrate Loading: This process increases glycogen stores in the muscles, which provide energy for prolonged, lower-intensity activities, such as long-distance running. As glycogen is the primary energy source during extended exercise, maximizing its storage can significantly enhance endurance.
Step 4
Suggest and explain how GLUT4 and CD36 transport proteins are beneficial during exercise.
Answer
GLUT4 and CD36 transport proteins are beneficial during exercise for the following reasons:
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GLUT4 Activation: During exercise, the influx of calcium ions stimulates the translocation of GLUT4 to the plasma membrane of muscle cells. This increases glucose uptake, providing a vital energy source to support muscle contractions.
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CD36 Function: CD36 facilitates the transport of fatty acids into the mitochondria during exercise. Fatty acids can then be oxidized to generate ATP, especially during prolonged exercise when muscle glycogen stores may be depleted.
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 an increase in heart rate due to the following mechanisms:
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Increase in Carbon Dioxide: As muscle activity levels rise, there is an associated increase in carbon dioxide (CO2) production. This change is detected by chemoreceptors in the body.
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Signal to Cardiac Centre: These chemoreceptors send more nerve impulses to the cardiac centre in the medulla oblongata, prompting an increased heart rate.
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Greater Blood Flow Demand: The increase in heart rate helps to supply the working muscles with more oxygenated blood, enhancing their performance and supporting the increased rate of respiration and ATP production.