33 — The Biochemistry of Movement (25 marks) Answer parts (a) and (b) of the question on pages 2–4 of the Section II Writing Booklet - HSC - SSCE Chemistry - Question 33 - 2015 - Paper 1

Adenosine triphosphate (ATP) is crucial for cellular processes as it serves as the primary energy currency of the cell. Structurally, ATP consists of an adenine base, a ribose sugar, and three phosphate groups. The high energy bonds between the phosphate groups store energy, which is released during hydrolysis to ADP and inorganic phosphate. This energy is used to drive various biochemical reactions, enabling vital cellular functions.

To investigate the effect of temperature on enzyme activity, a practical experiment can be designed as follows:

1. Prepare a series of solutions containing the enzyme and its substrate.
2. Set water baths at varying temperatures (e.g., 0°C, 20°C, 37°C, 60°C).
3. Add the enzyme solution to each substrate solution in the water baths and measure the rate of reaction, typically by observing product formation over a fixed time period.
4. Repeat the experiment multiple times for accuracy and to average the results.
5. Analyze the data to observe how temperature influences enzyme activity, with a focus on optimal temperature ranges.

Models play a crucial role in elucidating enzyme function, showcasing their mechanisms and interactions at a molecular level. These models can highlight the lock and key hypothesis, which conceptualizes enzyme specificity, or the induced fit model, demonstrating how enzymes undergo conformational changes upon substrate binding. The advantages of such models include helping to visualize complex processes, testing theories through simulated reactions, and providing insights into enzyme active sites. However, limitations exist, such as the challenges in accurately representing biological conditions and the simplification of intricate biochemical processes.

Two examples of bonding in the protein structure include hydrogen bonds and disulfide bridges.

1. Hydrogen bonds occur between polar amino acid side chains, stabilizing secondary structures like alpha helices and beta sheets, thus contributing to the overall shape of the protein.
2. Disulfide bridges form between the sulfhydryl groups of cysteine residues, providing significant stability to the protein's tertiary structure. The strength of these bonds aids in maintaining the protein's specific conformation crucial for its function.

The protein can be denatured through several factors.

1. High temperature can disrupt the hydrogen bonds and interactions that stabilize the protein's structure, leading to unfolding.
2. pH changes can alter the charge of the amino acid side chains, disrupting ionic bonds and hydrogen bonding, ultimately affecting the protein's shape.
3. Chemical agents, such as urea, can disrupt interactions among amino acids, leading to denaturation. The disruption of these intermolecular forces alters the functional conformation of the protein.

During sprinting, the body primarily utilizes the anaerobic glycolysis pathway, as it requires immediate energy and oxygen supply is limited. This results in rapid ATP production but also generates lactate as a byproduct, leading to fatigue. In contrast, when walking at a gentle pace, the body primarily relies on aerobic respiration, using oxygen efficiently to metabolize glucose and produce ATP through the Krebs cycle and oxidative phosphorylation. This pathway supplies energy steadily, reducing lactate accumulation and allowing for sustained activity over longer periods.