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Enzymes are…
* Biological catalysts
Lower the energy level needed for a biochemical reaction to occur. This energy level is called activation energy. * Proteins
Polypeptide chains made up of 100’s-1000’s of amino acids in a specific sequence. * Do not get “used up” in a reaction
The number of “uses” of an enzyme depends on the enzyme. * Work more efficiently at certain optimum temperatures.
* They are “reaction-specific”. Each enzyme is included in one reaction. Many biochemical processes/pathways required multiple enzymes. * Speed up reaction by binding to substrate (reactant) forming an enzyme-substrate complex. * Series of enzymes in each reaction, in a specific sequence. * Each enzyme has an “active site” that bonds to a substrate. Some toxins bind to these active sites, preventing the biochemical reactions from occurring. * Denaturation.

* Enzymes can change their shape (slightly).

Catalyst: A substance that speeds up a chemical reaction.
Polypeptide (Chain): Protein.
Peptide: Amino acids.

Collision Theory

* Chemical reactions occur by substances/particles “colliding” with each other. * The collisions require 2 components to be “successful” (e.g. form a new component). 1. Collisions need sufficient speed/energy.

2. Collisions require correct orientation (have to hit at the correct angle). * Enzymes bind to substrates = this helps to “ensure” correct angle/orientation higher percentage of collisions will result in a reaction.

Induced Fit Model
* Enzymes can slightly alter their shape in order to bund to a substrate. * After the enzyme has finished in the reaction, it returns to its original shape.

Lock and Key Model
* Enzymes have a fixed shape. In order to bind to specific substrates. * Only the correct activation site on a specific substrate can bind with the enzyme. * Except that proteins are NOT fixed, rigid structures.

Enzymes Require…
* Optimum...
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