Maintaining a Balance
1. Most organism are active in a limited temperature range
The role of Enzymes in metabolism, their chemical composition and specificity on substrates
Role of enzymes * Enzymes are organic catalysts. They are protein molecules that increase the rate of the reactions in living organisms. * Without enzymes, metabolic reactions at body temperatures would be too slow to produce sufficient energy to maintain life * Intracellular enzymes are used in the cells that produce them e.g cellular respiration or photosynthesis * Extracellular enzymes act outside producer cells e.g. digestive enzymes.
Chemical composition * Enzymes are proteins made of amino acids linked and folded to produce a 3D structure specific to a certain substrate * Composed of carbon, hydrogen, oxygen and nitrogen * Each enzyme catalyses a distinct chemical reaction in which it combines with the substrate to form an enzyme substrate molecule upon which the substrate is broken down * One model used to illustrate the action of an enzyme is the lock-key model. This is where only one small part of the enzyme molecule can form a complex with the substrate. This part of the molecule is called the active site. Only a specific substrate can bond in that site and this makes the enzyme specific to that substrate. * The induced fit model, a more recent modification on the lock-key model, proposes that the active site slightly changes its shape to accommodate the substrate perfectly.
Factors affecting enzyme activity * Temperature * Increased temperature causes increased reaction rate as molecules move more rapidly and collide more with the enzymes active site * If temperature is too high, the enzyme denatures and can no longer bind with substrate * Substrate concentration * The higher the substrate concentration the higher chance of collision with the enzyme active site * pH * each enzyme is specific to a