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Enzymes. The biological catalyst. What is an Enzyme?. Enzymes are catalysts that are produced by living organisms. A catalyst speeds up chemical reactions without being changed by the reaction itself. Enzymes are globular proteins which act as catalysts in chemical
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Enzymes The biological catalyst
What is an Enzyme? • Enzymes are catalysts that are produced by living organisms. • A catalyst speeds up chemical reactions without being changed by the reaction itself. • Enzymes are globular proteins which act as catalysts in chemical reactions in living things.
Chemical processes would occur at a rate that is too slow for living organisms if enzymes were not involved. • Cells can control their metabolism by controlling the enzymes they produce. • During these chemical reactions, one or more substrates are catalysed by an enzyme into a product.
Enzymes are composed of long chains of amino acids that have folded into a very specific three-dimensional shape which contains an active site. • An active site is a region on the surface of an enzyme to which substrates will bind and which catalyses a chemical reaction involving the substrate.
Enzyme-Substrate Specificity • The active site of each enzyme has a very specific and intricate shape and it also has distinct chemical properties that match those of its substrate. • Not only does the substrate molecule fit the shape of the active site but it is also chemically attracted to it.
This is known as enzyme-substrate specificity. The enzyme and substrate fit together like a key fits a specific lock. The enzyme is the lock and the substrate is the key.
Effects on Enzyme Activity • Enzymes can be affected by three different factors in their environment. • A change in these factors can affect the rate at which the enzyme will work or they can render it ineffective. • Enzymes must have the right conditions they need in order to work effectively. • Enzyme activity is affected by temperature, pH, and the concentration of the substrate.
Temperature • Enzyme activity will increase as temperature increases (often doubles with every 10˚C rise). • At a higher temperature more collisions occur between the substrate and the enzymes due to faster movement of molecules. • However, at high temperatures enzymes are denatured and stop working. • High heat causes vibrations inside the enzymes which break bonds needed to maintain the structure of the enzyme.
PH • As pH levels increase or decrease from the optimum level for each specific enzyme, the activity level is reduced. • Both acids and alkalis can denature enzymes. A pH of 7 is optimum for most enzymes.
Substrate Concentration • Enzyme activity is directly proportional to substrate concentration at low concentration levels. • As the concentration of the substrate rises, the enzyme activity increases because random collisions of substrate molecules and enzymes increases as the concentration of the substrate increases. • At high substrate concentrations, all the active sites of the enzymes will be occupied so raising the concentration level will no longer have an effect.
Denaturation • Denaturation is changing the structure of an enzyme (protein) that results in the loss (usually permanent) of its biological properties. • This means it can no longer carry out its function. • Denaturationoccurs as a result of a change in temperature or pH.
Lactose free milk • Enzymes are a very important part of biotechnology, which is the use of organisms or parts of organisms to produce things or carry out useful processes.
Lactose is a dissacharide found in milk. • The enzyme lactase is used to break it down into glucose and galactose (two monosaccharides). • Under normal circumstances the human body produces enough lactase to break down any lactose consumed in the diet.
Biotechnology companies culture a particular species of yeast known as Kluyveromyceslactis which grows naturally in milk. • These yeast produce lactase which the companies extract and purify to sell to food manufacturing companies.
Lactase can be added to milk to break down lactose into glucose and galactose. • This is very helpful to people who are lactose intolerant. • People who are lactose intolerant do not produce enough lactase to break down the lactose found in milk and milk products. • By adding lactase to milk, the lactose is broken down before it is consumed therefore making the milk product lactose-reduced and it can be consumed by an individual with lactose intolerance.
