Enzymes

Definition

Enzymes are biological catalysts that speed up chemical reactions in living organisms by lowering the activation energy required for the reaction to occur. They are typically proteins that are highly specific for their substrates, which are the reactants they act upon, and they play crucial roles in metabolic processes and cellular functions.

5 Must Know Facts For Your Next Test

1. Enzymes can be affected by temperature and pH, with each enzyme having an optimal temperature and pH range for maximum activity.
2. Enzymes can be regulated by molecules that enhance or inhibit their activity, allowing cells to control metabolic pathways effectively.
3. Some enzymes require cofactors, such as metal ions or coenzymes, to function properly, highlighting their complex nature.
4. Enzymes follow the lock-and-key model or the induced fit model to explain how substrates bind to active sites, which allows for specificity in reactions.
5. Enzymes are not consumed in the reactions they catalyze, meaning they can be used repeatedly for many cycles of substrate conversion.

Review Questions

• How do enzymes lower the activation energy of a chemical reaction?
  • Enzymes lower the activation energy of a chemical reaction by providing an alternative pathway for the reaction to occur. They achieve this by binding to the substrate at their active site, facilitating a transition state that requires less energy than the un-catalyzed reaction. This means that more molecules can successfully react at lower temperatures, speeding up the overall reaction rate.
• Discuss the impact of temperature and pH on enzyme activity and why these factors are important for biological processes.
  • Temperature and pH significantly impact enzyme activity because each enzyme has an optimal range for functioning. Deviations from this range can lead to decreased activity or denaturation of the enzyme. For example, high temperatures may cause an enzyme to lose its structure and thus its ability to bind substrates, while extreme pH levels can disrupt ionic and hydrogen bonds critical for maintaining the enzyme's active site. Understanding these factors is crucial as they affect metabolic processes and overall cell function.
• Evaluate how the specificity of enzymes contributes to metabolic regulation in living organisms.
  • The specificity of enzymes is essential for metabolic regulation as it ensures that only certain substrates are transformed into products without interference from other molecules. This selectivity allows cells to maintain order and efficiency within complex biochemical pathways. Additionally, regulatory mechanisms, such as allosteric modulation or competitive inhibition, can alter enzyme activity in response to cellular needs, ensuring that metabolic processes adapt to changing conditions without causing unwanted side reactions.

Related terms

substrate: The specific reactant molecule upon which an enzyme acts.

active site:

The region on an enzyme where the substrate binds and undergoes a chemical reaction.

cofactor: A non-protein molecule that assists enzymes in catalyzing reactions, often by stabilizing the enzyme or participating in the reaction.