Enzymes

Basic Features Speed up chemical reactions in your body Made of protein Act by lowering activation energy for reactions “Lock and Key” method Very specific (only do one reaction) Can be reused!

Can be denatured (destroyed) by: (a) Increasing Temperature (usually over 55C enzyme is destroyed) (b) Changing pH out of optimum range (c) Adding heavy metals (ex. Pb, Hg)

Enzyme Diagrams… Ea = Activation Energy: Energy required to cause molecules to react with one another Without Enzyme A: Activation energy without an enzyme B: Activation energy with an enzyme C: Overall energy released during reaction *An enzyme LOWERS the Ea! Reactants With Enzyme Products

Substrate: Reactant(s) in an enzymatic reaction Active site: Area of enzyme that binds with substrate Enzyme: Acts as a CATALYST Products: Freed and enzyme is available to be used again “Lock and Key” Model  Each enzyme is SPECIFIC and fits its substrate PERFECTLY Enzyme-Substrate Complex: When enzyme and substrate are bound

Types of Reactions Degradative: substrate is broken into smaller pieces Example- peptide  amino acids Synthesis: substrates are joined to form larger molecules Example- glucose  glycogen Metabolic Pathway: Series of reactions that proceed in an orderly manner - Each reactant is a substrate for a particular enzyme

Naming Enzymes Enzymes are often named for their substrate Ex. SUBSTRATE ENZYME Maltose Maltase Ribonucleic Acid Ribonuclease

“Induced Fit” Model Differs from “Lock and Key” Active site undergoes shape change to perfectly fit substrate Once product(s) release, active site returns to original shape

Stopping Enzyme Activity Feedback Inhibition Competitive Inhibition - Another molecule competes with true substrate for the active site Non-Competitive Inhibition - Another molecule binds to enzymes at a site other than the active site (called an ALLOSTERIC SITE) - Changes 3D shape of the enzyme  can no longer bind to substrate

Feedback Inhibition (competitive or non competitive) What’s happening? End product is binding allosterically to Enzyme 1 This changes the active site shape  the pathway is SHUT DOWN

Enzyme Composition Made up of 2 parts: Apoenzyme (protein part) Coenzyme OR Cofactor (non protein part) Dietary Dietary Organic Inorganic Vitamins Metallic ions Ex. K Ex. Ca2+

Example- Thyroxin Hormone produced by thyroid gland Increases metabolic rate in cells Increases # of respiratory enzymes in cells Cause increase in O2 uptake

Graphing Enzyme Activity We’ll discuss some common curves together for the following parameters: Temperature pH Substrate or enzyme concentrations

Temperature Activity increases due to increased kinetics At a max temperature, enzyme starts to denature Leads to rapid decrease in enzyme activity

pH Enzymes operate in a narrow pH range As you move above or below this range, enzyme activity decreases due to denaturation Ex. Enzyme pepsin works best at pH 2 (in the stomach)

Concentration Activity increases as substrate concentration increases Due to greater likelihood of molecular collisions Plateau  all active sites are occupied (enzyme is operating at capacity)