KS4 Chemistry. Biotechnology. Contents. Biotechnology. Introducing biotechnology. Enzymes. Fermentation. Other uses of biotechnology. Summary activities. What is biotechnology?. Living things use chemical reactions to produce new materials.
Living things use chemical reactions to produce new materials.
Biotechnology is the use of these reactions by humans to manufacture useful products.
Biotechnology is also about genetically modifying living things to produce medicines, and to introduce useful characteristics into plants and animals.
What products are made using biotechnology?
Almost all chemical reactions that take place inside living things are controlled by enzymes.
Enzymes are biological catalysts. They speed up chemical reactions without being used up.
Every cell in every plant and animal contains many different types of enzyme. Each enzyme catalyzes a different reaction.
Enzymes are very large and complex molecules made of protein.
This is a computer-generated model of an enzyme molecule. The small particle on the left is the reactant molecule.
Enzymes are very specific about what reaction they catalyse. Only molecules with exactly the right shape will bind to the enzyme and react. These are called reactant molecules, or the substrate.
The part of the enzyme with which the reactant binds is called the active site.This is a very specific shape.
The reactant is said to fit like a ‘key’ in the ‘lock’ of the enzyme’s active site. This way of describing how an enzyme works is called the ‘lock and key’ model.
Enzyme-catalyzed reactions take place across a range of temperatures, usually 20-45°C.
All enzymes work best at only one particular temperature, called the optimum temperature. Different enzymes have different optimum temperatures.
As the temperature decreases below the optimum, the reaction slows down and the enzyme will eventually become inactive. The reaction will stop.
As the temperature increases above the optimum, the reaction quickly slows down and stops completely. This is because the temperature irreversibly alters the shape of the enzyme and stops it working.
At this point, the enzyme is said to be denatured.
Enzyme reactions occur across a range of pH values.
Like for temperature, each enzyme will work best at only one particular pH.
Some enzymes, for example, those in the stomach, work best in acidic conditions. Other enzymes work best in alkaline conditions.
If the pH value changes sufficiently, the enzyme’s shape irreversibly changes and it will be denatured.
CO2 (g)What is fermentation?
Yeast cells contain enzymes that converts sugars (such as glucose and sucrose) into alcohol (ethanol) and carbon dioxide.
This reaction is called fermentation.
Fermentation usually takes place at 20-30°C. It must take place in anaerobic conditions (without oxygen) otherwise the ethanol would react with oxygen and turn into vinegar.
Fermentation has been used for thousands of years in brewing and baking.
Grapes are crushed to release their juice, which contains the glucose.
The juice is fermented under anaerobic conditions by the natural yeast on the grape skins.
The enzymes in the yeast convert the glucose to alcohol.Fermentation and wine-making
Barley grains are warmed with water to germinate. This produces sugar.
Barley is boiled with water
to release the sugar.
Hops are added for flavour.
Yeast is added and enzymes in this convert the sugar to alcohol.
Beer is usually filtered and the yeast recycled to make more beer.
Flour is mixed with water, yeast, salt and sugar to make a dough.
The dough is left in a warm environment to allow fermentation.
Fermentation produces carbon dioxide gas, which makes the dough rise.
The bread is baked, killing the yeast and evaporating the alcohol. Holes are left in the mixture where the CO2 gas expanded.
Pasteurized or sterilized milk is used to kill unwanted bacteria.
The milk is mixed with specially-cultured bacteria and kept warm.
The enzyme lactase from the bacteria convert milk sugar (lactose) into lactic acid, which gives a sour taste and makes the product semi-solid.
Like yoghurt, cheese is made from cow’s milk. Goat or sheep’s milk can also be used.
Specially-cultured bacteria are added to sour the milk.
A type of enzyme called a coagulant, such as rennet, is added. This forms solid curds and liquid whey.
Whey, mainly water and lactose, is removed. The curd is salted, moulded and pressed to become cheese.
Biological washing powders contain enzymes to help remove stains.
The enzymes are coated with a special wax. This melts in the wash, releasing the enzymes. Once the stains have been broken down, they are easier to remove by the detergent.
A type of enzyme called isomerase converts the sugar glucose into fructose, another type of sugar.
Fructose is sweeter than glucose, so a smaller amount is needed. This makes fructose syrup a useful ingredient in slimming foods.
Invertase is used to create soft-centered chocolates. The centre initially contains sucrose (cane sugar) and is hard. The invertase breaks down the sucrose into the simpler sugars glucose and sucrose, making the centre soft and runny.
Another type of enzyme called carbohydrase converts starch syrup (e.g. from potatoes) into sugar syrup, for use in sweets, soft drinks and baking.
Enzymes are becoming more common as catalysts for industrial processes. Why is this the case?
What are the steps in the production of an enzyme-catalyzed reaction?
1. Find or bioengineer microbes (e.g. bacteria, yeast) that produce the required enzymes.
2. Make a solution containing the nutrients the microbes need to grow, and the reactant.
3. Add a small amount of the microbe to the solution. Keep warm, correct the pH and provide oxygen if necessary.
4. The enzyme will catalyse the reaction, converting reactant into product.
5. Separate the product.
stainless steel reactor
Large-scale enzyme reactions require a continuous, rather than a batch, process.
Reactants are constantly being fed in and products are constantly being removed.