Enzymes and Chemical Reactions

Chemical reactions involve changing molecules, either by bonding or breaking bonds.
Reactions require positioning molecules in an unstable state.
Changing molecules involves creating an unstable state for the reaction to occur.
Reaching this unstable state requires absorbing energy from the environment.
Energy is needed to change bonds, whether forming or breaking them.
Forming or breaking bonds often generates disorder (entropy) in the environment by releasing heat.
When new bonds are formed, energy is released as heat.
The products are in a lower energy state after the reaction.

The amount of energy needed to supply for a reaction can be graphed.
The energy required to initiate a reaction is the activation energy.
Providing heat increases kinetic energy, leading to faster molecular collisions and a higher chance of reaction.
Heat can also cause bonds to vibrate, making them easier to break.
The unstable state is called the transition state.
Transition: A change from one stable form to another, where the likelihood of bonds breaking or forming is high.
Activation Energy: The energy required to contort the reactant molecules so bonds can break.
$Activation Energy = Energy Required to Reach Transition State$

Enzymes lower the activation energy, speeding up reactions.
Enzymes interact directly with reactants.
For example, breaking down a large polysaccharide into simple sugars (monomers) requires enzymes to speed up the reaction.
Enzymes are biological catalysts; they speed up chemical reactions by lowering the activation energy.
Enzymes are not consumed by the reaction; they are recycled.
Enzymes can become saturated, reducing their overall effectiveness.

Enzymes, being proteins, have unique shapes (conformations).
An enzyme's primary structure (amino acid sequence) determines its conformation.
Enzymes act on substrates.
The substrate interacts with the enzyme at its active site.
Enzymes are specific; they only catalyze substrates that complement their active site.
Lock and Key Model: The substrate fits perfectly into the active site.
Induced Fit Model: The active site changes shape slightly when the substrate binds to it, optimizing the interaction.
Why does the active site change shape?
- To hold the substrate in place.
- To increase the number of bonds between the substrate and active site.
- To optimize the interaction and strengthen bonds.

Enzymes speed up chemical reactions in the cell.
The active site is where enzyme activity takes place.
Enzymes bind to molecules called substrates.
The enzyme converts the substrate into a different product or products.
After the reaction, the products are released, and the enzyme is free to act on another substrate.
Enzymes have optimal environmental conditions for maximum activity (e.g., pH, temperature).
When conditions are less than optimal, an enzyme can lose its configuration and slow its activity, called denaturation.

Enzymes provide a template for reactions to align correctly.
Enzymes create strain or stress and bend bonds required for the reaction.
They create microenvironments (e.g., changing pH or temperature) ideal for the reaction.
Enzymes may be directly involved in the reaction by forming bonds with the substrates.
Enzymes are found in aqueous environments (e.g., cells, stomach, blood).