Factors Affecting Enzymes: Temperature, pH, substrate & Enzymes concentration and Inhibitors.

Factors Affecting Enzyme Action

Temperature

• Impact of Temperature on Enzymes

  • Low temperatures result in insufficient kinetic energy leading to fewer successful collisions between enzyme active sites and substrates.

  • This results in lower rates of reaction due to fewer enzyme-substrate complexes formed.

• Denaturation at High Temperatures

  • High temperatures increase kinetic energy, causing the enzyme to denature.

  • Denaturation refers to the alteration of the active site's shape due to broken bonds in the tertiary structure.

  • Denatured enzymes do not form enzyme-substrate complexes, similarly resulting in a decreased reaction rate.

pH Levels

• Effect of pH on Enzyme Activity

  • Enzymes can denature at extreme pH levels (too high or too low).

  • Excess hydrogen (H+) ions at high pH or hydroxide (OH-) ions at low pH alter the charges on amino acids in the active site.

  • Disruption of ionic and hydrogen bonds leads to a change in enzyme shape (denaturation), reducing enzyme-substrate complex formation and lowering reaction rates.

  • Each enzyme has a specific optimal pH; for example, amylase functions best in slightly alkaline conditions, while proteases perform optimally in acidic conditions.

Substrate and Enzyme Concentration

• Substrate Concentration

  • At low substrate concentrations, the reaction rate is slow due to limited collisions between substrate and enzyme.

  • As substrate concentration increases, the reaction rate rises, indicating the substrate concentration is a limiting factor until it saturates the enzyme active sites.

  • Beyond saturation, the rate levels off because enzyme concentrations become the limiting factor due to full utilization of active sites.

• Enzyme Concentration

  • Similar relationship: low enzyme concentrations slow reaction rates due to insufficient active sites.

  • As enzyme concentration increases, the reaction rate improves until all substrate active sites are saturated, resulting in a plateau due to empty active sites.

Inhibitors

• Definition

  • Inhibitors are molecules that bind to enzymes, hindering their action and slowing down reaction rates.

• Competitive Inhibitors

  • Structurally similar to substrates and compete for binding at the active site to form an enzyme-inhibitor complex.

  • Increasing substrate concentration can outcompete the inhibitor, restoring normal reaction rates.

• Non-Competitive Inhibitors

  • Bind to a site other than the active site, altering the enzyme's tertiary structure and changing the shape of the active site.

  • This prevents substrate binding even with increased substrate, resulting in a consistent lower maximum rate of reaction compared to no inhibitor present.

Graphical Representation in Exams

• Graph Understanding for Enzyme Action

  • Typical enzyme-catalyzed reaction graphs demonstrate rates with/without inhibitors.

  • Competitive inhibitors show an initial lower rate but can reach the same endpoint at high substrate concentrations.

  • Non-competitive inhibitors show a distinctly lower plateaued rate that remains irrespective of substrate concentration increase.

Here are the flashcards converted to Q&A format:

1. Q: What is the effect of temperature on enzymes?A: Low temperatures decrease kinetic energy, leading to fewer successful collisions between enzyme active sites and substrates, resulting in lower rates of reaction.

2. Q: What is denaturation in enzymes?A: Denaturation refers to the alteration of an enzyme's active site's shape due to high temperatures or extreme pH levels, leading to decreased enzyme-substrate complex formation.

3. Q: How do pH levels affect enzyme activity?A: Extreme pH levels can denature enzymes by disrupting ionic and hydrogen bonds, altering charges on amino acids and reducing reaction rates.

4. Q: How does substrate concentration affect reaction rates?A: At low substrate concentrations, reaction rates are slow; as concentration increases, rates rise until enzymes are saturated.

5. Q: How does enzyme concentration influence reaction rates?A: Low enzyme concentrations lead to slow reactions; increasing enzyme concentration raises reaction rates until all substrate active sites are saturated.

6. Q: What are competitive inhibitors?A: Competitive inhibitors are molecules that compete for binding at the active site, slowing reaction rates but can be overcome by increased substrate concentration.

7. Q: What are non-competitive inhibitors?A: Non-competitive inhibitors are molecules that bind to a site other than the active site, altering enzyme structure and preventing substrate binding, leading to a consistent lower reaction rate.

8. Q: What do enzyme-catalyzed reaction graphs illustrate?A: Typical graphs show rates of reactions with and without inhibitors; competitive inhibitors show lower initial rates but normal endpoints, while non-competitive inhibitors show a consistently lower plateau.