ENZYMES

ENZYMES

WHAT ARE THEY?
1. Proteins made in cells and may be intracellular or extracellular.
2. Biological Catalysts that speed up the Rate of Reaction. They are not used up in the process. Particular Enzymes only catalysis a particular reaction, so they are very specific.
3. They are Tertiary structure Globular Proteins and dependent on binds formed between R groups.
4. Energy required to start a reaction is called Activation Energy. Enzymes lower this energy for a biological reaction to proceed.
5. They don't always break things down, they can put Substrates together.
LOCK AND KEY HYPOTHESIS
1. The Active Site region on the Enzyme has a complementary shape to the Substrate.
2. The Subsrate binds to the Enzyme's Active Site forming an Enzymes-Substrate Complex. The reaction then takes place and Products are formed. Then the Enzyme is used again as it collides with an other Substrate.
INDUCED FIT MODEL
1. The Substrate alters the shape of the Active Site on the Enzyme when it binds.
IMMOBILISED ENZYMES
1. Fixed, bound or trapped Enzymes in an inert Matrix such as a gel capsule.
2. Using Immobilised Lactase to Hydrolise Lactose in milk to produce Glucose and Galactose (Lactose free Milk).
3. Used in Fermentation and Washing Powders (encapsulate Enzyme in wax if people are allergic).
4. Used also in making Baby Food, Pectinases break down Pectin in the cell walls of fruit and vegetables.
5. Biosensors are Medical Devices that measure concentration of a Specific Metabolite within a mixture. When a mixture is passed over the Enzymes, a reaction occurs. Because Enzymes are specific to a given Substarte, Glucose Biosensor is highly accurate ast detecting Glucose levels, even at low concentrations. Diabetics can use a Glucose Biosensor to test blood sugar levels.
6. Immobilised Enzymes can be re-used so are cheaper than Free Enzymes. They can tolerate a wide range of Conditions, like higher temperatures and pHs. They can be easily removed and added so there is more control over the Rates of Reaction. More than one Enzyme with a different Optima can be used together. Product can be easily recovered without contamination.
7. They have a slower Rate of Reaction and Substrate can only penetrate beads - maybe surface Enzymes only Catalyse reactions.
RATE OF REACTION
1. The Higher the Enzyme Concentration, the more likely for a successful collision with a Substrate (provided there is a high concentration of Substrate). Until all Substrate is used up and the rate stays the same.
2. Higher the Concentration of Substrate, the more successful collisions will take place. Rate of Enzyme Catalysed reaction increases as the concentration of the Substrate increases up to a maximum point where the concentration of Enzymes is limiting, the rate will then Plateau.
3. At low temperatures, Enzymes are inactive so are few Enzyme-Substrate Complexes. At high temperatures, there is an increase in kinetic energy so are more successful collisions. This occurs up until the Optimum temperature has been reached. Over the optimum temperature of the Enzyme breaks the Hydrogen bonds and the tertiary structure changes, the Active Site then changes as the Enzyme has denatured and the Substrate can no longer fit .
4. Most Enzymes are effective in a narrow pH range, within this range, one particular pH will be the optimum where the Enzyme works best. Any change in pH decreases the rate of reaction. Changes affect Ionic and Hydrogen bonds holding the Enzyme's Tertiary Structre. Large changes from the Optimum causes the Active Site to change shape and denature and small changes cause reversible changes in structure.
5. Competitive Inhibitors of a particular Enzyme is complimentary to its Active Site so can block the Substrate from binding. It can be overcome by increasing the Concentration of Substrate. If there is a higher Concentration of Inhibitor, the rate will be reduced as more successful collisions would occur between the Enzymes and Inhibitor as it binds to the Active Site.
6. Non-Competitive Inhibitors is not complimentary and doesn't bind to the Active Site. It binds to the Allosteric Site, but as it does, it causes the Enzyme's Active Site to change. So Substrates can no longer fit. Even if Substrate Concentration is high, the Inhibitor will still have affect on the rate as the Optimum rate will never be reached. The Inhibitor can still successfully bind to the Enzyme as it isn't competing for the same site as the Substrate.

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