Enzymes Notes

Enzymes

Catalysis

• Enzymes are biological catalysts produced by all living cells.
• They accelerate chemical reactions within organisms without being altered.
• Life would be unsustainable without enzymes due to slow reaction rates.

Properties of Enzymes

• Catalytic Property
• pH Sensitivity
• Reversibility
• Heat Sensitivity
• Specificity

Enzymes are Proteins

• Enzymes are proteins made from amino acids, which animals obtain from their diet and plants manufacture.
• Enzymes are globular proteins with a tertiary structure.
• Enzymes have an active site.

Enzymes are Specific

• Enzymes catalyze only one type of reaction.
• Each enzyme has specific substrates.

Active Site

• Enzymes possess an active site, where a substrate molecule binds, similar to a lock and key.
• Chemical bonds form between the substrate and the active site, facilitating the reaction.
• Example: Amylase catalyzes the breakdown of starch into sugars:
  starch + water \xrightarrow{amylase} sugars
• The starch molecule is attacked by a water molecule and weakened by its bonds to the enzyme and is hydrolyzed into two.
• This process repeats until all starch is broken into sugar molecules.

Temperature and Enzyme Activity

• Enzymes operate optimally at a specific temperature, known as the optimum temperature.
• High temperatures can denature enzymes, altering their shape and rendering the active site incompatible with the substrate.
• The optimum temperature for enzymes in the human body is typically around 37°C.
• Denaturation may begin around 40°C-45°C.

pH and Enzyme Activity

• Enzymes function best at a particular pH, known as the optimum pH.
• For most enzymes, the optimum pH is around 7.
• Extremes in acidity or alkalinity can denature enzymes.

Vitamins and Minerals

• Vitamins and minerals can aid enzyme function.
• Example: Vitamin B1 assists respiratory enzymes.

Enzyme Inhibition

• Certain poisons can inhibit enzyme action.
• Examples: Arsenic and cyanide.

Examples of Enzymes

• Amylase: Catalyzes the breakdown of starch into sugars:
  starch \xrightarrow{amylase} maltose
• Found in saliva, pancreatic juice, and germinating seeds.
• Catalase: Catalyzes the breakdown of hydrogen peroxide into water and oxygen:
  2H2O2 \xrightarrow{catalase} 2H2O + O2
• Present in most cells to prevent the harmful buildup of hydrogen peroxide.

Properties of Enzymes Summarized

• Biological catalysts
• Lower activation energy
• Increase the rate of reaction
• Proteins
• Remain unchanged after a reaction
• Specific to a substrate (Lock and Key)
• Reversible
• Denatured by changes in temperature and pH
• Optimum temperature and pH (e.g., 37°C and pH 7 in humans)

Effects of pH on Enzymes

• Extremely high pH denatures enzymes.

Optimum Temperature

• The optimum temperature is the temperature at which the enzyme exhibits the highest activity.