Enzymes are proteins that act as biological catalysts, speeding up chemical reactions in living things. They have an active site that attracts and binds to specific substrate molecules. Once bound, the enzyme-substrate complex undergoes a shape change that either breaks or forms bonds in the substrate. This releases the product and returns the enzyme to its original shape to catalyze more reactions. Enzymes lower the activation energy needed for reactions and are regulated through cofactors, inhibitors, feedback inhibition, and subcellular localization.

1. ENZYMES made of proteins biological catalysts (speed up reactions) act on molecules (substrate) to break them down/build them up most enzymes’ names end in –ase

2. Anatomy of an enzyme

3. How Enzymes Work Induced Fit Model Active site on enzyme draws substrate(s) closer (attracted by functional gp) Active site shaped to only bind to a specific substrate(s), like lock and key Sub(s) get drawn into cleft of enzyme Once bound, Enzyme-Substrate Complex (ES Complex) is formed.

4. ES Complex changes shape slightly either breaking or binding sub. molecule(s) End product released and enzyme returns to original shape, able to bind more sub. YouTube - Enzyme

5. Activation Energy the amount of energy (without enzymes) needed to start a reaction (usually high) enzymes lower amnt of activation energy needed

6. Enzyme Co-factors non-protein component of enzymes help enzyme to catalyze by binding to active site or substrate 2 types: Co-enzymes – organic molecules - ex. NAD + (vitamin B derivative) Inorganic Ions – ex. Ca 2 +, Zn 2 +…

7. Enzyme Inhibitors Inhibit (slow down/stop) enzyme activity This prevents build up of wastes in cell 2 kinds: Reversible - controls enzyme activity by action on either substrate or end product Irreversible – permanently destroys active site

8. Reversible Enzyme Inhibitors 3 types Competitive Inhibitor – binds to active site to prevent substrate from binding Video: enzyme (biochemistry) :: Competitive inhibitors prevent enzymes from catalyzing with substrates -- Britannica Online Encyclopedia

9. ii) Noncompetitive Inhibitor – binds somewhere other than active site, causes enzyme to change shape and slow down reaction Tutorial 6.1 Enzyme Catalysis iii) Allosteric Enzyme Inhibitor – binds to enzyme somewhere other than active site, causing enzyme to change shape and stops reaction Tutorial 6.2 Allosteric Regulation of Enzymesl

10. Irreversible Enzyme Inhibitors permanently destroys active site ex. Some heavy metals like Hg, Cd, Pb, As

11. Regulation of Enzyme Activity Feedback Inhibition a product formed in a sequence of reactions inhibits an enzyme that catalyzes a substrate earlier in the reaction inhibitor binds to enzyme, slowing down production (non-competitive inhibitor) as production slows down, amount of inhibitor available decreases until used up so enzyme can start binding and producing again

12. soon amount of inhibitor in product increases enough to inhibit production again continues in a constant loop to control the reaction Feedback Inhibition of Biochemical Pathways 2. Location of Enzyme some enzymes kept in cellular compartments until needed