Life Sciences - Term 4 - Week 8

Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are typically proteins that lower the activation energy required for reactions to occur. Each enzyme has a specific active site that binds to its substrate, forming an enzyme-substrate complex. This specificity is crucial for metabolic pathways, as it ensures that reactions occur in a controlled manner.

The mechanism of enzyme action involves several steps: substrate binding, formation of the enzyme-substrate complex, and product release. When a substrate binds to the active site of an enzyme, it induces a change in the enzyme's shape, facilitating the conversion of substrate into product. This process is often described by the 'lock and key' model or the 'induced fit' model, highlighting the importance of the enzyme's structure in its function.

Enzyme activity can be influenced by several factors, including temperature, pH, and substrate concentration. Each enzyme has an optimal temperature and pH at which it functions best. Deviations from these conditions can lead to decreased activity or denaturation of the enzyme. Additionally, increasing substrate concentration generally increases the rate of reaction until the enzyme becomes saturated.

Consider the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. At optimal conditions (around 37°C and neutral pH), catalase can significantly speed up this reaction. If we were to increase the temperature beyond 37°C, we might observe an increase in reaction rate up to a point, after which the enzyme could denature, leading to a decrease in activity.

In pairs, students will investigate the effect of pH on the activity of amylase, an enzyme that breaks down starch into sugars. Using starch solution and iodine, students will set up experiments at different pH levels (acidic, neutral, and basic) and measure the time taken for the blue-black color to disappear, indicating starch breakdown. Discuss the results as a class and relate them to enzyme structure and function.

Students will choose an enzyme of their choice and research its role in a specific metabolic pathway. They should focus on the enzyme's structure, function, and the factors affecting its activity. Each student will prepare a short presentation summarizing their findings, which will be shared with the class in the following week.

• To provide energy to cells
• To catalyze biochemical reactions
• To transport molecules across membranes
• To store genetic information

Answer: To catalyze biochemical reactions

Enzymes act as catalysts that speed up chemical reactions without being consumed in the process.

• Temperature
• pH
• Substrate concentration
• Color of the enzyme

Answer: Color of the enzyme

The color of the enzyme does not influence its catalytic activity; however, temperature, pH, and substrate concentration do.

Answer: The 'lock and key' model suggests that the enzyme's active site (the 'lock') is specifically shaped to fit a particular substrate (the 'key'), ensuring that only the correct substrate can bind and undergo a reaction.

This model emphasizes the specificity of enzymes for their substrates.

• It becomes more active
• It denatures
• It increases its substrate affinity
• It remains unchanged

Answer: It denatures

Extreme temperatures can disrupt the hydrogen bonds and other interactions that maintain the enzyme's structure, leading to denaturation.

• To provide energy for the reaction
• To bind substrates and facilitate the reaction
• To transport the enzyme within the cell
• To store the enzyme's genetic information

Answer: To bind substrates and facilitate the reaction

The active site is the region of the enzyme where substrate binding occurs, allowing the enzyme to catalyze the reaction.

Answer: Temperature and pH.

Both temperature and pH can influence the shape and function of enzymes, affecting their activity.