Question 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

ATP is crucial for energy transfer within cells. Its structure consists of three phosphate groups connected to an adenosine molecule. The bonds between these phosphate groups are high-energy bonds. When ATP is hydrolyzed, the energy released is utilized in various cellular processes such as muscle contraction, active transport of molecules across membranes, and biosynthetic reactions. The conversion of ATP to ADP and inorganic phosphate is a key reaction that powers many physiological functions.

1. Prepare multiple test tubes, each containing an equal amount of enzyme solution and substrate.
2. Set each tube at different temperatures (e.g., 0°C, 20°C, 37°C, and 60°C) using water baths.
3. Allow each tube to equilibrate at the set temperatures for 5 minutes.
4. Add the substrate to each test tube and start a timer.
5. Measure the rate of product formation at regular intervals using appropriate methods (e.g., spectrophotometry).
6. Record the data to determine how temperature affects enzyme activity by analyzing the rate of reaction in each condition.

Models are essential in biochemistry as they simplify complex biological processes, allowing researchers to visualize enzyme actions. For instance, the lock-and-key model illustrates how substrates fit into active sites, while the induced-fit model suggests that enzyme flexibility enhances substrate binding. Furthermore, these models can demonstrate enzyme kinetics and identify factors affecting enzyme activity. However, limitations exist, such as oversimplifying cellular interactions or not accounting for environmental variables affecting enzyme function.

1. Disulfide Bonds: The sulfur atoms in cysteine residues form disulfide bonds, providing stability to the protein's tertiary structure by linking different regions together.
2. Hydrogen Bonds: These bonds between the carbonyl oxygen and amine hydrogen of peptide bonds help maintain the secondary structure (such as alpha-helices and beta-sheets) of the protein, contributing to its overall three-dimensional conformation.

1. Temperature: Extreme heat can disrupt weak interactions within the protein, leading to unfolding. For example, an increase from room temperature to boiling can break hydrogen bonds.
2. pH Changes: Alterations in pH can affect ionic bonds and lead to changes in charge, resulting in the protein losing its shape. A drastic pH shift can denature the protein by disrupting interactions stabilizing its structure.

Sprinting primarily relies on anaerobic metabolism due to the rapid energy demand, utilizing glycolysis followed by lactic acid fermentation, producing ATP quickly but leading to lactic acid build-up. In contrast, walking utilizes aerobic metabolism, engaging pathways such as the TCA cycle and oxidative phosphorylation, providing a sustained energy supply with lower lactic acid levels. Thus, sprinting reflects a short-term energy strategy, while walking emphasizes endurance and efficient energy use.