Enzymes: Detailed Notes

ENZYMES

• Biological (protein) catalysts that speed up metabolism.

WHAT ARE ENZYMES?

• Enzymes are biological catalysts.
• They are proteins that speed up chemical reactions.
• Not permanently changed during a reaction, so they can be reused again.

HOW DO ENZYMES WORK?

• Enzymes work by weakening bonds, which lowers activation energy.
• The energy required to start a chemical reaction is drastically reduced.
• For example, a chemical reaction required 1500 joules of energy; with an enzyme, the requirement can decrease to 1000 joules of energy.
• The body would utilize less energy and would have to consume less.
• Think of it as a discount! With an enzyme, it's like 33% off!

HOW ENZYMES AFFECT ENERGY REQUIREMENT!

• Diagram illustrating the progress of a reaction with and without an enzyme.
• Shows the reduction in free energy of activation when an enzyme is used.

HOW ENZYMES AFFECT SPEED OF REACTION

Energy

• Reactants (e.g., C6H12O6 + O2)
• Activation energy without enzyme
• Activation energy with enzyme
• Overall energy released during reaction
• Products (CO2 + H2O)

Time

• Time reduced by half the amount.

PROPERTIES OF ENZYMES

• Enzymes are highly specific; they require the perfect:
  • Substrate
  • Temperature
  • pH
• When all conditions are met, it is called the OPTIMUM CONDITION.

SPECIFICITY OF ENZYMES

• Enzymes can only bind to molecules that have a distinct shape.
• These molecules are known as SUBSTRATES.
• ENZYMES bind with SUBSTRATES due to their complimentary shape and react to make PRODUCTS.
• The region where enzymes bind is called the ACTIVE SITE.
• When enzymes bind to substrates, it's called the ENZYME SUBSTRATE COMPLEX!

LOCK AND KEY MODEL

• An enzyme binds to a substrate at the active site due to their complimentary shapes, just like a key (substrate) fits to a lock (enzyme).
• An enzyme substrate complex is formed, after which a chemical reaction occurs, and the substrate is converted or turned into products.
• The enzyme remains unchanged at the end of a chemical reaction.

Substrate Catalysis

• Enzyme + Substrate -> Enzyme-Substrate Complex -> Enzyme-Product Complex -> Enzyme + Product

LOCK AND KEY MODEL (Diagrammatic Representation)

• Key (substrate) fits into Lock (enzyme) forming a Lock-Key Complex (Enzyme-Substrate Complex).

ENZYME TEMPERATURE RELATIONSHIP

• Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity.
• A higher kinetic energy will result in more frequent collisions between the enzymes and substrates.
• At an optimal temperature (may vary for different enzymes), the rate of enzyme activity will be at its highest; most products are formed at this temperature.
• Higher temperatures will cause enzyme stability to decrease, causing the enzyme (particularly the active site) to lose its shape, resulting in the loss of activity (denaturation).
• Once denatured, the enzyme can not return to its normal state even if temperatures are brought to optimal levels.

HOW TEMPERATURE AFFECTS ENZYMES

• Enzymes work best at a specific temperature.
• If the temperature of the environment exceeds the specific temperature, the active site of enzymes DENATURES (deforms), leading to a loss in enzyme reactivity as substrates can no longer bind and form ES-Complexes.
• The enzymes can never work, even if the temperature was placed at optimum again. The effect is irreversible.

HOW pH AFFECTS ENZYMES

• Changing the pH will alter the charge of the enzyme, which in turn will alter protein shape.
• Optimum pH produces the most products.
• Changing the shape or charge of the active site will diminish its ability to bind the substrate as the active site denatures.
• The effect of pH on enzyme is reversible.

USE OF ENZYME IN REAL LIFE

• What Do Enzymes Do for You?

SECTOR, APPLICATION AREA, BENEFITS

• Detergents: Household washing and cleaning agents. Benefits: Wash your clothes in cold water; make your teeth cleaner.
• Textiles: Denim washing, silk polishing, leather goods softening. Benefits: Stonewash your jeans; make cotton look and feel like silk; make your leather soft.
• Food processing: Baking, brewing, fruit juice. Benefits: Clarify your juice and beer; make bread better; turn corn starch into sugar syrup.
• Pulp and paper processing: Starch conversion, pitch control, bleach-boosting, deinking, stickies control, slime control. Benefits: Reduce production costs and improve quality.
• Other Sectors: Biocatalysis, Household items, Biotech R&D, Biofuels, Diagnostic, Canola, Pharmaceuticals, Food & Beverage, Animal Feed

DETERGENTS AND ENZYMES

• Enzymes are naturally occurring substances that act as catalysts for certain biochemical reactions.
• When placed in laundry detergent, certain enzymes can target specific types of stains and break the soiled mass into smaller molecules that eventually wash away.
  • Protease: Breaks down protein-based stains.
  • Amylase: Gets rid of starch or carbohydrate stains.
  • Cellulase: Removes stains by breaking down cotton fibers.
  • Lipase: Breaks down fat-based stains.
  • Pectinase: Removes stains from fruits and other similar substances.
• Enzymes work best when used in cooler water temperatures.
• Enzyme detergents can clean clothing more effectively with less detergent.