Enzyme Structure and Functions:

ENZYME STRUCTURE AND FUNCTIONS Enzymes argon biological catalysts. They cast up the enjoin of answers by a factor of between 106 to 1012 times, al upseting the chemical reactions that thrust feel possible to take place at normal temperatures Definition of enzyme A protein with catalytic properties due to its power of specific activation is defined as an enzyme. STRUCTURE Enzymes ar proteins their function depends on its complexity. The reaction takes place in a small part of the enzyme called the alive(p) invest, while the rest of the protein acts as scaffolding.The shape and the chemical environment inside the energetic site permits a chemical reaction to proceed more easily many an(prenominal) enzymes need cofactors (or coenzymes) to work properly. Tightly bound cofactors ar called prosthetic groups Cofactors that be bound and released easily are called coenzymes These fundament be metal ions (such as Fe2+, Mg2+, Cu2+) or organic corpuscles (such as haem, biotin, F AD, NAD or coenzyme A). Many of these are derived from dietary vitamins, which is why they are so important. The complete alert enzyme with its cofactor is called a holoenzyme, while just the protein part without its cofactor is called the apoenzyme.HW DOES AN ENZYME WORK? 1) REACTION MECHANISM 2) molecular(a) GEOMETRY REACTION MECHANISM In any chemical reaction, a substratum (S) is converted into a product (P) In an enzyme-catalysed reaction, the substratum first binds to the active site of the enzyme to form an enzyme-subst graze (ES) complex, then the subst treasure is converted into product whilst habituated to the enzyme, and finally the product is released, thus allowing the enzyme to start all over over again An example is the action of the enzyme sucrase hydrolysing sucrose into glucose and fructose.MOLECULAR GEOMETRY The substrate molecule is antonymous in shape to that of the active site. It was thought that the substrate exactly cope withted into the active site of the enzyme molecule like a key fitting into a lock (the now discredited lock and key theory). This explains enzyme specificity This explains the loss of natural action when enzymes denature The Induced Fit Hypothesis * Some proteins house swap their shape ( class) When a substrate combines with an enzyme, it induces a change in the enzymes conformation * The active site is then moulded into a precise conformation * Making the chemical environment suitable for the reaction * The bonds of the substrate are stretched to make the reaction easier (lowers activation zipper) ENERGY CHANGES Energy needed for initial reaction is known as ACTIVATION ENERGY. The larger the activation faculty is, the slower the reaction will be.This is because only a few substrate molecules will have sufficient energy to overcome the activation energy barrier. Enzymes reduce the activation energy of a reaction so that the energising energy of around molecules exceeds the activation energy required and so they hatful react. Factors affecting Enzymes substrate concentration pH temperature enzyme concentration inhibitors SUBSTARTE CONCENTRATION The rate of an enzyme-catalysed reaction is also affected by substrate concentration.As the substrate concentration increases, the rate increases because more substrate molecules can collide with active sites, so more enzyme-substrate complexes form. At higher concentrations the enzyme molecules become saturated with substrate, and there are few free active sites, so adding more substrate doesnt make much difference The maximum rate at infinite substrate concentration is called vmax, and the substrate concentration that gives a rate of half vmax is called KM.These quantities are useful for characterising an enzyme. A good enzyme has a high vmax and a low KM. pH Enzymes have an optimum pH at which they work fastest. For most enzymes this is about pH 7-8 (normal body pH), but a few enzymes can work at extreme pH. The pH affects the charge of th e amino acids at the active site, so the properties of the active site change and the substrate can no bimestrial bind. TEMPERATURE Enzymes have an optimum temperature at which they work fastest.For mammalian enzymes this is about 40C. Up to the optimum temperature the rate increases geometrically with temperature. preceding(prenominal) the optimum temperature the rate decreases as more of the enzyme molecules denature. The thermal energy breaks the total heat bonds holding the secondary and tertiary mental synthesis of the enzyme together, so the enzyme loses its shape Q10 (the temperature coefficient) = the increase in reaction rate with a 10C initiate in temperature. ENZYME CONCENTRATIONAs the enzyme concentration increases the rate of the reaction also increases, because there are more enzyme molecules (and so more active sites), available to catalyse the reaction therefore more enzyme-substrate complexes form INHIBITORS Inhibitors inhibit the activity of enzymes, reducing the rate of their reactions. 2 TYPES Competitive and non competitive COMPETITIVE A competitive inhibitor molecule has a similar structure to the substrate molecule, and so it can fit into the active site of the enzyme. It therefore competes with the substrate for the active site, so the reaction is slower.Increasing the concentration of substrate restores the reaction rate and the inhibition is usually improvised and reversible. NON COMPETITIVE A non-competitive inhibitor molecule is quite different in structure from the substrate and does not fit into the active site. It binds to another part of the enzyme molecule, ever-changing the shape of the whole enzyme, including the active site, so that it can no longer bind substrate molecules. Non-competitive inhibitors therefore simply reduce the amount of active enzyme.