ENZYMES

Enzymes Most, but not all end in the suffix …ase Participate in reactions but are not used up or changed in any way …although they can eventually “wear out” Can perform either catabolic (destructive) reactions. eg. 1 substrate = 2 products Can perform either anabolic (constructive) reactions. eg. 2 substrate = 1 products

Enzymes … Act at both the intra and extracellular level Act on SUBSTRATE and yield PRODUCT Reduce the ACTIVATION energy required to start a reaction in the body Are very specific, each individual type of substrate is acted upon by a specific enzyme Are very specific, each individual type of substrate is acted upon by a specific enzyme Generally names are based on the specific substrate (eg lipids acted upon by lipase)

Enzyme Structure Enzymes have an active site and a regulatory region The active site is where substrate binds to the enzyme The regulatory region is where cofactors coenzymes or enzyme inhibitors can alter the function of an enzyme Substrate Active site Regulatory region Products Enzyme inhibitor

Enzymes – inhibitors / cofactors Enzyme inhibitors can be either competitive or non-competitive A competitive inhibitor blocks the substrate from entering the active site A non-competitive inhibitor binds to the regulatory region, thereby changing the shape of the active site Other enzymes will not work unless a particular cofactor occupies the regulatory region

The “Lock and Key” model of enzyme activity The enzyme provides a perfect fit for a particular substrate

The “Induced Fit” model of enzyme activity The substrate induces the enzyme to change shape to create a tighter fit

Factors Affecting Enzyme Activity pH Most biological enzymes operate at a neutral pH range of 6-8 If enzymes are at a pH outside their optimum range, their shape will change and they will be less efficient. Enzyme Cells Carbonic Anhydrase TrypsinPepsin LocationBloodSmall Intestine Stomach Opt. pH

Factors Affecting Enzyme Activity Temperature Most biological enzymes have an optimum temperature of 37° If an enzyme is exposed to temperatures higher than optimum, it will permanently denature. If an enzyme is exposed to temperatures lower than optimum, it will become inactive until temperature returns to optimum. The enzymes of other organisms have optimum temperatures suited to the environment in which they live

Effect of temperature

Factors Affecting Enzyme Activity Enzyme Concentration An increase in enzyme conc. will cause an increase in reaction rate but won’t increase the yield. Substrate concentration Reaction rate will initially increase as unoccupied enzymes take on substrate but will then plateau. Inhibition Other molecules can block the active site or regulatory region of an enzyme.

Increasing substrate concentration