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Proteins and enzymes (Ezymes (Properties of enzymes (Enzymes are effected…
Proteins and enzymes
Ezymes
They are biological catalysts that speed up the rate of reaction by lowering the activation energy needed for a chemical reaction
Enzymes lower the activation energy of a reaction by forming enzyme substrate complexes with the substrate and put pressure on certain areas causing bonds to break more efficiently (less energy required) allowing the reaction to be undertaken at lower temperatures
Enzymes are proteins which have a specific 3D tertiary structure which includes a specific active site that is complimentary to the enzymes substrate
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The model
Induced fit model:
The active site is not fully fixed and the substrate induces a change in the shape of the active site making it complimentary
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4) Once the products leave the active site it returns to its previous shape allowing more substrate molecules to bind to it
Properties of enzymes
Enzymes are effected by: Temperature, pH, Inhibitors, Substrate concentration, Enzyme concentration
Effect of temperature: Every enzyme has a temperature at which it works best (Optimum) after the enzyme has passed the optimum temperature the enzyme denatures and can no longer form enzyme substrate complexes
Effect pH: pH is a measure of hydrogen ion concentration a change in pH means a change in the concentration of hydrogen ions similar to temperature there is an optimum pH and after the optimum the pH the enzyme denatures and is no longer complimentary
Effect of substrate concentration: As the substrate concentration increases the rate of reaction until it no longer becomes the limiting factor
Effect of enzyme concentration: The more enzyme molecules that are in the solution the more likely to collide with the available substrate and form the enzyme substrate complexes increasing the rate of reaction
Proteins
Protein structure
A high increase in temperature will cause the protein to denature which changes the 3D tertiary structure of the protein which means it will no longer be specific to its substrate
Quaternary structure: Some proteins consist of 2 or more polypeptide chains joined together. A common example is Haemoglobin which has 4 polypeptide chains
Tertiary structure: This is further folding off the secondary structure into a specific complex 3D shape. This structure is maintained by 3 different types of bonding, Hydrogen bonds the weakest, Ionic bonds also weak which form between oppositely charged R groups, disulphides bridges, covalent bonds, which form between sulphur containing R groups. The tertiary structure of the protein is essential for its function. The shape of the protein determines how it reacts with other molecules
Secondary structure: This is the folding of the polypeptide into an alpha helix or beta- pleated sheet. This structure is maintained by hydrogen bonds between the amine group of one amino acid and the carboxyl group of another
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Biuret test for proteins
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2) If a colour change from blue to lilac occurs a protein is present if there is no colour change there is no protein present