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Enzymes as proteins
Reflections and Exam tips
Proteins are organic compounds containing the elements Carbon, Hydrogen, Oxygen and Nitrogen. They are similar to carbohydrates in that they share Carbon, Hydrogen and Oxygen but have additional Nitrogen.
Proteins are made up of small units called amino acids, these are joined together by ribosomes during protein synthesis.
Proteins and DNA
Proteins are made from instructions from DNA. DNA consists of 4 bases, the instructions are copied from the Nucleus and translated into proteins in the cytoplasm.
Uses of proteins in living things
Enzymes are proteins which speed up chemical reactions inside living things. They are biological catalysts.
How do they work?
Enzyme + Substrate —› enzyme-substrate complex —› Enzyme + product
Enzymes are either named using family names or specific names.
Enzyme family names derive from the substrate that the enzyme catalyses, just add ...ase at the end.
Specific names of enzymes
Each enzyme acts on one specific chemical/substrate hence they have more specific names.
Factors affecting rates of enzyme reactions
Enzymes are made up of proteins, (so they are a bit fragile), they are affected by anything which affects their movement or changes the shape of the active site.
As the temperature increases, the kinetic energy of the enzyme and substrate molecules increases, this means that the rate of the reaction also increases as chances of active sites and substrates joining up (colliding) increase.
The temperature at which the enzyme works best is called the optimum temperature. Above the optimum temperatur,e too much vibrations of the atoms within the enzyme breaks the bonds holding the active site together. The substrate cannot fit anymore and the reaction stops.
We say the enzyms has been denatured.
Most enzymes have an optimum temperature of around 40°C.
pH is how acidic or alkaline the surroundings are. Each enzyme acts within a very narrow pH range, a change in pH disrupts the bonds which hold the active site. the anzyme is denatured.
You can easily tell the optimum pH of an enzyme by checking where it works in the body. As a guide these are the pHs around the body:
Mouth = around pH7 (+-1)
Stomach =around pH2
Small intestine = around pH 7.5 (can be slightly more alkaline to pH8)
Blood = around 7.4
3. Substrate concentration
As the substrate concentration is increased, the rate of reaction increases up to a maximum point where it does not increase anymore. This is because at this point all active sites are occupied, new substrate has to wait for free active sites.
Industrial and domestic uses of enzymes
Why use enzymes?
Biological washing powders
Enzymes used in washing powders include:
Advantages of using enzymes in washing powders are:
But as noted earlier, enzymes are expensive.
Making fruit juice- pectinases
These digest the pectins, carbohydrates that form cell walls in fruits like oranges and apples, opening up cells and releasing more juice.
Isomerases- for making slimming foods
Proteases- For making baby foods