in amino acid chains • Biological catalysts (speed up reactions in living things without being used up • Either intracellular (inside the cell) or extracellular (outside the cell) • Their active sites shape is complementary to the shape of their substrate
active site because their shapes are exactly complementary • Forms a enzyme substrate complex • Once catalysed, the products are released • The enzyme’s shape is unchanged and can then bond with another substrate
a substrate is not exactly complementary, the active site of the enzyme will change shape to accommodate the substrate • Puts strain/stress/tension on the substrates bonds, making them more likely to break • Reduces activation energy
of the enzyme and substrate molecules • Increases the amount of successful collisions • Increases the amount of enzyme substrate complexes • Increases amount of products • Increase of rate of reaction • Temperature that the enzyme catalyses best is the optimum temperature • For many enzymes this is between 35 and 40°C
• The energy gained by the molecules is too much at the higher temperature and so the weak hydrogen bonds can break • Protein’s tertiary structure is altered and the enzyme changes shape • Active site changes shape so no substrate can bond • No enzyme substrate complexes formed • No products • Change is permanent
substrates in a fairly narrow range of pH • Each enzyme has a pH at which it catalyses the fastest, called its optimum pH • Mainly around pH 7 • Pepsin optimum is pH 2
In alkaline environments, the amino acids lose protons • pH concentration effects the ionisation of amino acids • At extremes of pH, the enzyme becomes denatured • Ionisation of amino acids changes • Ionic bonds break • Proteins tertiary structure alters and enzyme changes shape • Active site changes shape, so no substrate can bond • No enzyme substrate complexes formed • No products • Only slight changes can be reversed
enzymes, the rate of reaction will depend on the concentration of substrate • Increasing concentration will increase the chances of successful collisions • Increasing amount of enzyme substrate complexes • Increasing the amount of product
Less enzyme substrate complexes formed • Less product • Enzyme active sites are not working at full capacity • High concentration of substrate means more successful collisions • More enzyme substrate complexes formed • More product • There will be a point at which all active sites are occupied • Increasing concentration after this point will not affect the rate of reaction
• More active sites present • More successful collisions • More enzyme substrate complexes formed • More product • As time progresses, substrate concentration will decrease as the substrates will have been catalysed into products • Gradually decreases rate of reaction • Therefore, rate of reaction is fastest at the beginning when substrate concentration is in abundance
• Bonds with enzyme active site and prevents substrates from bonding (until it is released) • Reduces the rate of reaction • Same quantity of product would be produced but it would take longer • Substrates continue to bond with uninhabited active sites • If substrate concentration increases, the rate of reaction also increases • This is a reversible inhibition
not at the active site • They do not compete with the same site of the enzyme • Binding site is known as the allosteric site • Alters the shape of the enzyme, therefore altering the shape of the active site • Substrate can no longer bind to the active site • If substrate concentration increases, there will be no change to the rate of reaction • Irreversible inhibition
to function • Heavy metal ions (Mercury and Silver) cause disulphide bonds to break • Once broken, enzyme structure is irreversibly altered and no longer has catalysing properties
milk for those who are lactose intolerant • Immobilised sucrose can convert sucrose into much sweeter glucose and fructose to sweeten low calorie foods • Immobilised enzyme are fixed/trapped/bound to an inert matrix • Gel capsules (alginate beads) • Beads can be packed into glass column • Once the substrate is added it will react with the enzymes as it flows down the column • Once set up, the column can be reused
of pH and/or temperature • Are easily recovered for use again and again, thus reducing costs • Several enzymes with varying optimum pH or temperatures can be used simultaneously • Can easily be added or removed which gives greater control over the reaction
to select one type of molecule from a mixture even in low concentrations • Can be used as a rapid and accurate detection of minute traces of biologically important molecules • When a mixture is passed over immobile enzymes a reaction occurs • Energy is released in proportion to the concentration of substrate and is converted into electrical impulses • Produces an accurate digital display of concentration
to measure glucose concentration in a blood sample • The electrode probe has a partially permeable membrane with a specific enzyme immobilised and attached • Placed into the blood sample • If glucose is present, it diffuses across the membrane forming enzyme substrate complexes • The formation of a product in turn produces an electrical current which is picked up by the electrode (aka the transducer) • The current is read by a meter which produces a reading for blood glucose
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