ENZYMES (2/2) - Factors Affecting Reaction Rate

Summary

This video explains the key factors influencing enzyme activity, including substrate concentration, temperature, and pH. It details how enzyme activity increases with substrate concentration until saturation, peaks within an optimal temperature range, and declines when enzymes denature at high temperatures. The script also covers the role of pH in enzyme structure and function. Additionally, it touches on cellular control mechanisms like phosphorylation and glycosylation, the presence of enzyme activators and inhibitors, and how competitive, non-competitive, and uncompetitive inhibitors interact with enzymes to regulate their activity.

Takeaways

• 😀 Substrate concentration affects enzyme activity. Low concentrations result in little enzyme activity, while high concentrations can saturate the enzyme, leading to a plateau in activity.
• 😀 Enzyme activity increases with temperature due to more frequent molecular interactions, but excessive heat can cause enzymes to denature and lose function.
• 😀 pH affects enzyme activity by altering the enzyme’s 3D structure. Enzymes have an optimal pH range, and deviations can result in loss of function due to denaturation.
• 😀 Enzymes work best within their optimal temperature and pH ranges, which are specific to their environment and biological function.
• 😀 Cells regulate enzyme activity through post-translational modifications, such as phosphorylation and glycosylation, which can either activate or deactivate enzymes.
• 😀 The production and localization of enzymes are tightly controlled by the cell to ensure that only the necessary enzymes are produced and sent to the correct organelles.
• 😀 Digestive enzymes are specifically found in the stomach and are not present in the brain, demonstrating the specialized functions of enzymes in different cells.
• 😀 Enzyme inhibitors can decrease activity. Reversible inhibitors bind non-covalently to enzymes, while irreversible inhibitors bind covalently, reducing the active enzyme concentration.
• 😀 Competitive inhibitors compete with the substrate for the active site, while non-competitive inhibitors bind to allosteric sites, causing conformational changes that affect enzyme activity.
• 😀 Uncompetitive inhibitors only bind to enzyme-substrate complexes, preventing the enzyme from releasing its product and thus decreasing enzyme activity.
• 😀 Enzyme activity is not only influenced by environmental factors but also by cellular mechanisms that control enzyme concentration and function through various regulatory processes.

Q & A

What are the three important factors that impact enzyme catalysis?

The three important factors that impact enzyme catalysis are substrate concentration, temperature, and pH.

How does substrate concentration affect enzyme activity?

At very low substrate concentrations, enzymes are inactive and waiting for a substrate. At high concentrations, most enzymes are occupied, and additional substrates wait for a free enzyme. As substrate concentration increases, enzyme activity saturates.

Why does enzyme activity decrease at high temperatures?

As temperature increases beyond a certain point, enzymes start to denature, causing them to lose their functional shape, which decreases enzyme activity.

What is the relationship between enzyme activity and temperature?

Enzyme activity increases with temperature as molecules gain kinetic energy and interact more frequently. However, beyond an optimal temperature, enzyme activity decreases due to denaturation.

How does pH affect enzyme activity?

pH affects enzyme activity by altering the enzyme's structure. Enzymes have ionizable side chains and prosthetic groups, and changes in pH can break bonds that maintain the enzyme's secondary and tertiary structures, impairing its function.

What role does the active site of an enzyme play in catalysis?

The active site of an enzyme is where the substrate binds, and the enzyme catalyzes the reaction. The proper alignment and structure of the active site are critical for effective catalysis.

What are activators and inhibitors in the context of enzyme activity?

Activators increase enzyme activity, while inhibitors decrease it. Inhibitors can be reversible or irreversible, with reversible inhibitors binding non-covalently and irreversible inhibitors binding covalently.

What are the three major categories of reversible inhibitors?

The three major categories of reversible inhibitors are competitive, non-competitive, and uncompetitive inhibitors.

How do competitive inhibitors affect enzyme activity?

Competitive inhibitors compete with the substrate for access to the enzyme's active site, and they can only bind to enzymes that are not already bound to a substrate.

What is the function of non-competitive and uncompetitive inhibitors?

Non-competitive inhibitors bind to both free enzymes and those already bound to substrates, often altering enzyme activity by binding to an allosteric site. Uncompetitive inhibitors only bind to the enzyme when it is already bound to a substrate, preventing the enzyme from releasing its products.