ENZYMES Biological Puzzle Pieces

REMEMBER: What is a Catalyst? A chemical that increases the rate of chemical reactions without altering the products or being altered itself

A Little About Reactions… Chemical reactions occur when molecules within a system collide Adding thermal energy to a system increases kinetic energy Thus, molecules move faster and increase chances of collision CATALYSTS speed up reactions at LOW TEMPS, so additional energy is not needed!

ENZYMES A protein catalyst that is found in LIVING THINGS. Permit low-temperature reactions by reducing the amount of activation energy required. Enzymes are denoted using “-ase” as their ending. i.e. carbohydrases break down carbohydrates

How Do They Work? ENZYMES work on SUBSTRATES like a “puzzle piece” Each substrate combines with a specific enzyme Upon combination, the substrate changes and creates a new product Estimated 200,000 different reactions in your body, each using a specific enzyme/substrate

How Do They Work? “ACTIVE SITE” is the area of the enzyme that joins with the substrate. Imagine it as the “dock” This creates the “Enzyme-Substrate Complex”

Co-Stars COFACTORS: an organic ion that helps an enzyme combine with a substrate molecule COENZYME: an organic molecule synthesized from a vitamin that helps an enzyme combine with a substrate molecule.

FACTORS AFFECTING ENZYME REACTIONS

1. pH Certain enzymes function most effectively at specific pH ranges. i.e. PEPSIN: enzyme found in the stomach, works best at a low pH (b/c stomach is an acidic environment) i.e. TRYPSIN: enzyme found in the small intestine, works best at a high pH (b/c intestine is a basic area)

2. Substrate Concentration Because reactions happen due to collisions, higher numbers of substrates increase the likelihood of a collision between substrates and enzymes.

3. Temperature As stated earlier… Higher Temp. = Faster Reactions BUT!!... Why do reaction rates in human cells peak at 37 degrees?

3. Temperature Cont’d At higher temperatures, proteins change shape or are denatured. REMEMBER: Enzymes are PROTEINS So, at certain temperatures, ENZYMES change their shape or are destroyed all together This reduces the chance of enzyme-substrate combintation

4. Competitive Inhibition INHIBITORS are very similar in shape to substrates Thus, they bond with enzymes before substrates have a chance, reducing the function of the enzyme.