Enzyme Characteristics to Know for General Biology I

Enzymes are essential biological catalysts that speed up chemical reactions in living organisms. Understanding their structure, function, and regulation is crucial for grasping how life processes, like digestion and metabolism, operate efficiently within cells.

1. Definition of enzymes

   • Biological catalysts that speed up chemical reactions in living organisms.
   • Typically proteins, but some RNA molecules (ribozymes) can also act as enzymes.
   • Essential for various biochemical processes, including digestion and metabolism.

2. Protein nature of enzymes

   • Composed of long chains of amino acids folded into specific three-dimensional shapes.
   • The structure determines the enzyme's function and specificity.
   • Can be denatured by extreme conditions, losing their catalytic ability.

3. Substrate specificity

   • Enzymes are highly specific to their substrates, meaning they only catalyze specific reactions.
   • The specificity is determined by the enzyme's active site shape and chemical environment.
   • This ensures that enzymes only interact with the correct molecules in a cell.

4. Active site

   • The region on the enzyme where substrate molecules bind.
   • The shape and chemical properties of the active site are crucial for enzyme function.
   • Often involves a precise arrangement of amino acids that facilitate the reaction.

5. Enzyme-substrate complex formation

   • The temporary complex formed when a substrate binds to an enzyme's active site.
   • This interaction stabilizes the transition state, making it easier for the reaction to occur.
   • The formation of this complex is a key step in the catalytic process.

6. Catalytic function

   • Enzymes lower the activation energy required for a reaction to proceed.
   • They facilitate the conversion of substrates into products without being consumed in the process.
   • Enzymes can be reused multiple times, increasing the efficiency of metabolic reactions.

7. Lowering activation energy

   • Enzymes provide an alternative reaction pathway with a lower activation energy.
   • This accelerates the rate of reaction, allowing biological processes to occur at physiological temperatures.
   • The reduction in energy barrier is crucial for sustaining life.

8. Cofactors and coenzymes

   • Cofactors are non-protein molecules (metal ions or small organic molecules) that assist enzyme function.
   • Coenzymes are a type of cofactor, often derived from vitamins, that help in the transfer of chemical groups.
   • Both are essential for the activity of many enzymes.

9. Enzyme nomenclature

   • Enzymes are named based on the type of reaction they catalyze, often ending in "-ase."
   • The name may include the substrate or the type of reaction (e.g., lactase, amylase).
   • The International Union of Biochemistry and Molecular Biology (IUBMB) provides standardized naming conventions.

10. Factors affecting enzyme activity (pH, temperature, substrate concentration)

    • Each enzyme has an optimal pH and temperature range for maximum activity.
    • Deviations from these conditions can lead to decreased activity or denaturation.
    • Increasing substrate concentration generally increases reaction rate until the enzyme becomes saturated.

11. Enzyme inhibition (competitive and non-competitive)

    • Competitive inhibition occurs when an inhibitor competes with the substrate for the active site.
    • Non-competitive inhibition occurs when an inhibitor binds to a different site, altering enzyme function.
    • Both types of inhibition can regulate metabolic pathways and enzyme activity.

12. Allosteric regulation

    • Allosteric enzymes have sites other than the active site where molecules can bind, influencing activity.
    • Binding of an allosteric regulator can enhance (activator) or inhibit (inhibitor) enzyme function.
    • This regulation allows for fine-tuning of metabolic pathways in response to cellular conditions.

13. Enzyme kinetics (Michaelis-Menten equation)

    • Describes the rate of enzyme-catalyzed reactions as a function of substrate concentration.
    • The equation helps determine key parameters like Vmax (maximum reaction rate) and Km (substrate concentration at half Vmax).
    • Understanding enzyme kinetics is crucial for studying metabolic pathways and drug interactions.

14. Importance of enzymes in metabolic pathways

    • Enzymes are vital for catalyzing biochemical reactions necessary for life, including energy production and biosynthesis.
    • They regulate metabolic pathways, ensuring that reactions occur in a controlled and efficient manner.
    • Enzymes play a key role in maintaining homeostasis and responding to changes in the environment.