Biology, enzyme notes

Alternative transcript:

and Secreted out of the cell if necessary in ucsicics. at a active Site & enzyme a specific region of an enzyme where a substrate binds :] Substrate MOICCUICS Why do enzymes different shapes ? have what would happen If an active site was to change? an enzyme's Shape is determind by the sequence of amino acids In its structure, and the bonds which form between the atoms Of those molecules. be the specific 3D Shape is held together by bonds which may ! affected by varying environmental condicions eg. temperature, and PH If the specific shape of the active site was to change then a specific fit between the active site and subscrate would be rendered Impossible and the enzyme would be unable to catalyse said reaction - the enzyme has been irreversibly denatured! Enzymes cherefore have optimum working Conditions. ह normal heat PH moho? denatured What is activation energy? activation energy activation energy enzymes help bring the substrate molecules into the appropriate orientation (Forming an enzyme-substrate complex 1 to facilitate the formation Canabolic) or the breaking of bonds (catabolic) coform the Product (s) activation energy is the energy required to bring molecules together So that they will react with each other. Every chemical reaction has a barrier that has to be overcome before a reaction can occur amount of energy needed to initiate a metabolic reaction enzymes lower the activation energy required to initiate a metabolic reaction an enzyme lowers the activation energy of a reaction by bringing the substrate molecules into the appropriate orientation (forming an enzyme-substrate complex I to facilitate the formation or breaking of bonds to form the product (s) Explain the lock and key hypothesis Explain the Induced fit theory? mechanism of enzyme action the substrate (key) has a complementary shape to the active Site Clock) of the enzyme molecule, forming a temporary Structure-enzyme - Substrate complex. The products have a different Shape from the substrate and so once formed they leave the active site. The active site is now free to become attached to another substrate molecule. This model suggests that the shape of the active site is not quite complementary to that of the substrate. On binding to the enzyme, the substrate disturbs the shape of the enzyme and causes it to mold around the substrate. The new configuration affects the shape of the Substrate, thus lowering activation energy. INDUCED FIT MODEL substrate active site (1) Substrate enters active site of enzyme. enzyme changes shape slightly as substrate binds (2) Enzyme/substrate complex forms. (3) Substrate is converted to products. products (4) Products leave the active site of the enzyme. Enzyme Concentration Properties of enzymes the number of substrate molecules which an enzyme can act on in a given time it is called its turnover rate When investigating the effect of a given factor on rate, all Other factors should be kept constant and at optimum levels an increase in the enzyme concetration results in an increase in the rate of reaction provided all other factors are kept constant at their optimum levels. Rate of Reaction beyond a certain point however increasing the enzyme concentration no longer has any effect however as substrate concentration becomes a limiting Factor Enzyme Concentration at higher concentrations of enzyme the reactions are faster as there are plenty of active sites available effect on enzyme Concentration Rate of Reaction at high enzyme concentrations, adding more enzyme has no effect on the rate of reaction. Some other Factor eg. Substrate concentration is now the limiting Factor. at low enzyme concentration adding more enzyme increases the rate of reaction as it increases the chances of a substrate molecules colliding with an empty active site. Enzyme Concentration effects of substrate Concentracions ● Subsrate concentration Foragiven amount of enzyme the rate of an enzyme Controlled reaction increases with an increase in substrate Concentration. Rate of reaction maximum tumouer rate eventually the Substrate Concentration race of reaction levels off as all available active sites are in use. as substrate concentration increases the rate of a reaction increases as more of the active sices are in use. at low substrate concentration the reaction rate increases sharply with increasing substrate concentration because there is lots of Free enzyme available to react with the substrate. athiqh Subsrate concentration, the reaction rate leucis off as the enzyme active sites become saturated with Subscrate. there areless free enzymes to react with the added Substrate Cenzyme concentration has become a limiting Factor. Rate of reaction C Substrate Concentration Max rate approached as all active sites become filled Some active sites free at lower substrate concentrations Temperature Optimum temperature is the temperature at which most Subscrate is converted to product in the shortest time. Those enzymes which operate within our body naturally have an optimum temperature of around 37°c. However some thermophilic bacteria have enzymes with optimum temperatures OF 85 °C. Low cemperature: Increasing temperature increases the kinetic energy of the molecules, increasing the number of Collisions therefore increasing the rate of reaction. Rate of Reaction Molecules gain kinetic energy Optimum Temperature Enzyme is denaturing and loosing Catalyic abilities. Temperature effect of heat on Cnzyme Structure Increasing temperature increases kinetic energy of enzyme and substrate molecules. This increases the chances of Collisions between enzyme and substrate. Therefore more enzyme-substrate complexes are formed; this lcds to a faster rate of reaction. aboue optimum the kinetic energy causes enzyme molecules to vibrace so much that the internal bonds (e.g. hydrogen bonds /s-s) are broken. Enzyme is Denatured. If you heat the protein aboue its Optimum temperature bonds break meaning the protein looses its secondary and tertiary structure a 10°c rise in temperature doubles the rate of reaction PH is a measure of H* or OH IONS in a solution. Most enzymes Function efficiently over a narrow PH range any change abouc or below this range will result in Denaturing. optimum pH volue enzyme activity I 3 1 7 S рн 1 1 PH (1 trypsin pepsin intestinal enzyme (trypsin) have an optimum pH of about 7.5 (slightly alkalinc) enzymes in the stomach have an optimum pH of around 2 (pepsin) effect of pH on enzymes. Each enzyme also has an optimum pH-At either side of this optimum changes in pH will reduce activity. This is caused by changes in pH disrupting the bands that are important in determining protein shape lonic bonds, in particular are subject to disruption when in a non optimal PH. The furcher the PH is away from the optimum, the greater the degree of disruption to the bonding, until eventually denaturation results.