Enzymes - IGCSE Biology Revision Notes

What Are Enzymes?

• Definition: Enzymes are proteins acting as biological catalysts that speed up chemical reactions without being consumed in the process.
• Role: Essential for maintaining the rate of metabolic reactions necessary for life.
  • Without enzymes, digestion could take weeks, while with them, it takes hours.

Characteristics of Enzymes

• Catalysts: Speed up reactions by lowering the activation energy required.
• Specificity: Each enzyme is specific to a particular substrate (the molecule it acts upon).
• Biological Origin: Made in living cells.
• Reusability: Not used up in the reaction, so they can be used repeatedly.

How Do Enzymes Work?

• Enzyme-Substrate Complex: The substrate fits into the enzyme's active site, forming an enzyme-substrate complex.
• Product Formation: The substrate is converted into products which are then released, freeing the enzyme to bind with a new substrate.

Models of Enzyme Action

Lock and Key Model

• Enzymes have an active site specifically shaped to fit their substrate, like a key fits into a lock.

Importance of Enzymes in Biology

• Metabolic Processes: Ensure reactions occur at a rate that supports life.
• Digestive Processes: Enzymes like amylases, proteases, and lipases are crucial for digesting carbohydrates, proteins, and fats.

Factors Affecting Enzyme Activity

• Temperature: Each enzyme has an optimum temperature for activity.
• pH Levels: Each enzyme works best at a specific pH level.
• Substrate Concentration: Activity increases with substrate concentration, up to a point where it levels off.

Applications of Enzymes

• Industrial Uses: Widely used in industries for processes like brewing, cheese-making, and biofuel production.
• Medical Uses: Used in diagnoses and treatment, e.g., enzymes used in blood glucose tests.

Conclusion

Enzymes are vital for life, playing critical roles in both the biological processes within living organisms and various industrial applications. Understanding enzyme specificity and function can help in fields ranging from medicine to biotechnology.