Chapter 3: Enzymes & Biochemical Reactions

๐ŸŒŸ What Enzymes Are

Enzymes are biological catalysts โ€” proteins that speed up chemical reactions inside living organisms.

Key Characteristics

  • Specific โ†’ each enzyme works with one substrate

  • Reusable โ†’ not consumed in reactions

  • Fast โ†’ speed up reactions millions of times

  • Shapeโ€‘dependent โ†’ structure determines function

Enzymes work by lowering the activation energy, the energy needed to start a reaction.

๐ŸŒŸ How Enzymes Work

Enzymes bind to a molecule called a substrate at the active site.

Induced fit model process explanation with enzyme products outline ...

Steps of Enzyme Action

  1. Substrate enters active site

  2. Enzyme changes shape slightly (induced fit)

  3. Reaction occurs

  4. Products are released

  5. Enzyme is ready to work again

This is why enzymes are incredibly efficient.

๐ŸŒŸ Factors That Affect Enzyme Activity (EOCโ€‘Tested)

These ALWAYS appear on the EOC.

1. Temperature

  • Low temp โ†’ molecules move slowly โ†’ fewer collisions

  • Optimal temp โ†’ fastest reaction rate

  • High temp โ†’ enzyme denatures (loses shape) โ†’ stops working

Denaturation is irreversible.

2. pH

Each enzyme has an optimal pH.

Examples:

  • Pepsin (stomach) โ†’ acidic pH

  • Amylase (mouth) โ†’ neutral pH

Wrong pH โ†’ enzyme denatures.

3. Substrate Concentration

  • More substrate โ†’ faster reaction

  • Until enzyme becomes saturated

  • After saturation โ†’ rate levels off

4. Enzyme Concentration

More enzyme โ†’ faster reaction (if substrate is available).

๐ŸŒŸ Enzyme Inhibitors

Not always tested, but helpful for mastery.

Competitive Inhibitors

  • Block the active site

  • Compete with substrate

Noncompetitive Inhibitors

  • Bind elsewhere

  • Change enzyme shape

Both slow or stop reactions.

๐ŸŒŸ Why Enzymes Matter

Enzymes control every biochemical reaction in your body:

  • Digestion

  • DNA replication

  • Cellular respiration

  • Photosynthesis

  • Muscle contraction

  • Immune responses

Without enzymes, life would be too slow to exist.

๐ŸŒŸ Biochemical Reactions & Energy

Every reaction in the body involves energy transfer.

Exergonic Reactions

Release energy
Example: breaking down glucose

Endergonic Reactions

Require energy
Example: building proteins

ATP is the molecule that transfers energy between reactions.

๐ŸŒŸ Enzymes in Metabolism

Metabolism = all chemical reactions in the body.

Catabolic Reactions

Break molecules โ†’ release energy
Example: cellular respiration

Anabolic Reactions

Build molecules โ†’ require energy
Example: protein synthesis

Enzymes regulate both.