ENZYMES

Enzymes help with most chemical reactions in the body

Digestion requires Enzymes Amylase in salivary glands Pepsin in stomach Lipase and trypsin in small intestine

Enzyme supplements

Enzymes assist in 2 main type of reactions in cells Synthesis (make) compounds 2) Decomposition (break) compounds Both require energy

Synthesis using enzyme A + B + Enzyme = AB + Enzyme

Decomposition using enzyme CD + Enzyme = C + D + Enzyme

The enzyme catalase Peroxide kills cells Catalase aids decomposition of peroxide into water and oxygen in cells H2O2  H2O and O2

Activation energy Energy required for a chemical reaction to occur

Most chemical reactions in cells require too much energy to occur naturally

Enzymes Natural catalysts that lower the activation energy so a reaction can occur in a cell

Enzymes are very complex proteins Proteins are three dimensional

Terms Substrate - The molecule that the enzyme attaches to Active site - The spot on the enzyme that fits into the substrate

Enzymes have a specific fit Like a lock and key

Induced fit model Some enzymes adapt slightly to fit substrate better

Enzyme animation Claymation enzyme 30 secs http://www.youtube.com/watch?v=ybahzSjUpB0&feature=related Pacman Animation 2 mins http://www.youtube.com/watch?v=CZD5xsOKres

Enzymes are not used in the reaction Can keep working! Unless destroyed or denatured Heat, acid etc. can denature enzymes undoing the tertiary structure

Denaturing proteins Heat etc. will break bonds of protein tertiary structure. reversible

Enzyme Regulation Temperature pH Concentration of enzyme or substrate Inhibitors

Effect of TEMPERATURE Increased temperature increases particle motion This increases reaction rate. Enzymes work faster with increased temperature BUT Enzymes are proteins and above a certain temperature they denature (come apart)

Every enzyme has an optimal temperature Increased temperature increases reaction rate until denaturing occurs

Effects of pH Changes in pH also denature enzyme Change in pH change the ionization state of many amino acid R groups This can alter the active site and keep substrate from binding

Enzymes have an optimal pH Pepsin in stomach Trypsin in intestine

Effect of substrate concentration Increase in substrate, increases rate until enzymes saturated

Law of Mass action Enzyme catalyzed reactions can reverse. When product becomes more than substrate, reaction can reverse back to substrate Note: this does not happen in high exergonic reactions, too much energy required to reverse

Coenzymes A chemical required by an enzyme for proper functioning Binds to enzyme temporarily Coenzyme Q etc. Many vitamins are Coenzymes

Competitive inhibitor Blocks active site

Competitive inhibitor Slows the rate, but eventually substrate builds up and competitive inhibitor has no effect

Non Competitive inhibitor Attaches to enzyme in another spot which alters its active site

Non Competitive inhibitor

Allosteric enzymes Enzymes that can be altered by an non competetive inhibitor Can also be Promoters! That increase enzyme activity A product can act as a feedback inhibitor

Toxic substances are often enzyme inhibitors They stop important biological processes Ex cyanide, lead, mercury, pesticides

Peroxidase enzyme Peroxidase catalyses the breakdown of peroxide turnip peroxidase 2H2O2 ------------------------ 2H2O + O2 We will use an in our lab

Animations of enzymes http://www.kscience.co.uk/animations/anim_2.htm