31 Biotechnology _ Revision, Print

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- GCSE Bitesize Science - Biotechnology : Revision, Print

www.bbc.co.uk/schools/gcsebitesize/science/triple_edexcel/using_biology/biotechnology/revision/print/[10/21/2013 8:25:37 PM]

BBC Radio 1 BBC 1Xtra

Biotechnology is the alteration of natural molecules using

science and engineering to provide goods and services.

Enzymes are biological catalysts and can be used in foods as

well as washing powders. Biotechnology can be used to

improve crops and help people without enough food, but some

people are worried about the potential hazards of genetic

modification.

Fermentation

Fermentation reactions occur when microorganisms take in food and convert it

into substances which are useful to them. The

[microorganism:Another name for microbe. Microscopic (too

small to see) organisms such as bacteria and viruses.] also release waste

substances such as carbon dioxide.

The most common example of fermentation is when [yeast: Single-celled

fungus used in fermentation.] (Saccharomyces cerevisiae) a single-celled

fungus - converts sugar (glucose) into alcohol. Here are the word and balanced

formulae equations for this process:

glucose ethanol + carbon dioxide

To make the production of alcohol as efficient as possible, large vessels are used

to [cultivate: To farm crops or animals.] the yeast. These are called

[fermenter: Vessels used to cultivate microorganisms on a large

scale.] .

Vats in microbrewery

Science

Biotechnology

microorganisms

yeast

cultivate

fermenters

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The following conditions are maintained to maximise growth rates:

1. The fermenter is kept [aseptic: Containing nothing that could cause

disease, such as bacteria, viruses or fungi.] so only the desired

microorganism grows.

2. Nutrients are provided to ensure that the microorganisms always have

enough food to grow.

3. The optimum temperature and [pH: Scale of acidity/alkalinity. pH below 7

= acidic, pH above 7 = alkaline.] is maintained to ensure maximum growth.

4. There is an oxygen supply because most fermentation reactions are

[aerobic: With oxygen.] .

5. Agitation (stirring) takes place to ensure that the microorganisms, nutrients

and temperature are evenly distributed.

Microorganisms and food production

We use microorganisms to make a large number of our food and drink products

these include bread, yoghurt, cheese and alcohol.

Microorganisms are useful because:

they grow rapidly

they have DNA which is easy to manipulate

they can be grown in fermenters in almost any location (the local weather

doesnt normally affect their growth)

they can be grown using the waste products from other industrial processes

You need to know the following two examples of how we use microorganisms to

make foods.

Mycoprotein

This is a general name for all the protein that is grown from [fungus:A

large group of eukaryotic organisms that contain single celled yeasts, moulds and

mushrooms.] . It is commonly made in fermenters and grown from the fungus

Fusarium. This protein is used instead of meat in a large number of vegetarian

foods. Protein is important for growth and repair. Mycoprotein has the added

advantage of being low in fat.

Fermentation

aseptic

pH

aerobic

fungi


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Yoghurt

Making yoghurt also uses microorganisms. Here [bacteria: Single-celled

microorganisms, some of which are pathogenic in humans, animals and plants.

Singular is bacterium.] [fermentation: Type of anerobic respiration

carried out by yeast.] the milk and change it into yoghurt. Lactose is the main

sugar in milk and the bacteria convert this into lactic acid. This increased

[acidity: The level of acid in a substance - the amount by which a

substance's pH is lower than 7. Corrosiveness.] sours the milk, giving yoghurt

its sharp taste. The lactic acid also helps to thicken yoghurt.

Bacterial fermentation can be summarised by the following equation:

How yoghurt is made

In order to see this content you need to have both Javascriptenabled and

Flashinstalled.

Enzyme technology

Enzymes are biological catalysts. They increase the rate of chemical reactions

without being used up. They are used to make a large number of foods for us.

You need to know the following three examples.

Making sweets

The enzyme invertase (sometimes called sucrase) is used by confectioners to

make toffees, chocolates, mints and other soft centres. It is often produced by

[yeast: Single-celled fungus used in fermentation.] and breaks down the

sugar sucrose into two other sugars called glucose and fructose.

Washing powders

Many biological washing powders now have enzymes in them to help break

down and remove stains. The two types of enzymes used are:

proteases - which break down proteins into amino acids

carbohydrases - which break down carbohydrates into sugars

Vegetarian cheese

For many years, cheese was only made using the enzyme chymosin. This used

only to be obtained from the stomachs of calves and so strict vegetarians were

not able to eat cheese made using chymosin.

Now the chymosin is produced by microorganisms after they have been

[genetically-modified:An organism that has been

modified by humans through the introduction of useful genes from a different

species.] . This means that cheese made using chymosin from microorganisms

no longer contains animal products - and so vegetarians are able to eat it.

Quorn products

bacteria

ferment

acidity

yeast

genetically modified
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Biotechnology experiments

You need to know about the following four experiments.

Growth of yeast

To investigate the growth of yeast, add a standardised small amount of it to a

known volume of sugar solution in a series of test tubes. [incubate: To

keep a sample of microbes warm so that the cells reproduce quickly.] them at

different temperatures and measure the height of the froth produced. A higherlevel of froth indicates more [fermentation: Type of anerobic

respiration carried out by yeast.] . Notice that more froth is produced up to an

optimum temperature after which the amount of froth produced reduces.

Yoghurt making

To investigate yoghurt making, heat some milk in a beaker at 40C for a few

minutes. Add a starter [culture: In microbiology, a colony of microbes,

typically on an agar plate.] of bacteria (Lactobacillus), and cover and incubate

until it sets. You could check whether differences in temperature or [pH:

Scale of acidity/alkalinity. pH below 7 = acidic, pH above 7 = alkaline. ] affect

the time it takes for the yoghurt to set.

Production of lactose-free milk

Lactose is the main sugar in milk that is broken down into galactose and glucose

by the enzyme lactase. Measure out two identical volumes of milk. Add some

lactase to one and keep both volumes in the same conditions overnight. In the

morning use [Benedict's solution:A solution that can be

Man adding rennet to milk in order to make cheese

Fermentation by Yeast

Incubate

fermentation

culture

pH

Benedicts solution


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used to test for the presence of a reducing sugar (or the presence of an

aldehyde group).] to test for glucose - which should only be present in the milk

to which you added the enzyme.

Enzymes in food production

Pectin is a sugar which is found in the cell walls of plants. It is broken down by

the enzyme pectinase. Cut up two identical portions of fruit. Place one in a

beaker of water (the control) and the other in a beaker of water containing

pectinase. After five minutes filter both solutions and record the volume of liquid

produced. The portion of fruit exposed to the pectinase should produce more

liquid.

Recombinant DNA technology - Higher tier

This process involves moving the [gene: The basic unit of genetic material

inherited from our parents. A gene is a section of DNA which controls part of a

cell's chemistry, particularly protein production.] (or genes) responsible for

making a protein into a different organism. It commonly involves moving genes

into [bacteria: Single-celled microorganisms, some of which are

pathogenic in humans, animals and plants. Singular is bacterium.] which can

then be grown in huge numbers in [fermentation: Type of anerobic

respiration carried out by yeast.] . These will make large quantities of the

protein which can be collected.

All [insulin:A hormone that regulates the level of sugar in the blood. It

is produced in the Islets of Langerhans in the Pancreas.] used by people with

[diabetes:A serious disease in which the body is unable to regulate

blood sugar.] is now made in this way. In the past, it was made from the

pancreases of pigs and [oxen: The plural of ox. An ox is a bovine animal

(eg cow) that has been trained to pull something for humans. ] .

The process for making insulin using recombinant DNA technology is as follows:

1. The human gene for insulin production is identified and removed using

Benedict's test for sugars

Temperature and enzyme activity

gene

bacteria

fermenters

insulin

diabetes

oxen


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enzymes called restriction enzymes.

2. The same restriction enzymes are used to cut open a plasmid (a small,

circular section of [DNA: The material inside the nucleus of cells,

carrying genetic information. DNA stands for Deoxyribonucleic Acid.] ).

3. A ligase enzyme is then used to seal the human gene into the plasmid.

4. The plasmid is then inserted into a bacterium - which is grown into huge

numbers of bacteria that all produce the human insulin.

Restriction enzymes

Restriction enzymes do not cut directly across the double strand of DNA because

this would involve cutting any section of DNA into many different pieces and it

would not be easy to remove an entire gene.

Instead they cut across the double strands at two different places. The place

where they cut across the DNA is called a sticky end. Restriction enzymes can be

used to cut out specific genes, and also cut open places in the plasmid DNA

where the genes will fit exactly.

Fusion cell cloning

DNA


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Biotechnology and the world food supply

The population of the world is rapidly increasing as can be seen in the graph

below:

This rise in population is partly responsible for the lack of food that exists in

certain countries. Other reasons for the shortage of food include:

poor quality soils and water shortages

poverty - meaning people cant afford to buy seed or equipment to grow

crops

wars

To meet the demands of an increasing population, we must increase the amount

of food we produce. This can be done by conventional plant-breeding

programmes and pest management strategies. It can also be done by genetic

modification. This is when a section of [DNA: The material inside the

nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic

Acid.] is moved from one [organism:A living being - plant, animal,

fungus or bacterium.] into another.

There are several common examples of genetic modification:

Sweet potato

This diagram shows the action of sticky ends.

Human population growth over the last 10,000

DNA

organism


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Vitamin A deficiency - which is common in some African and south-east Asian

countries - often leads to blindness in children. To combat a deficiency in this

particular vitamin, scientists have produced a sweet potato with increased levels

of vitamin A.

Purple tomatoes

Tomatoes have now been genetically modified to have an

[antioxidant:A chemical that prevents another chemical from

reacting with oxygen.] pigment called anthocyanin (a type of

[flavonoid:A group of chemicals found in plants that cause specific

colours and have biochemical roles.] ). This is thought to have anti-cancer

properties. It is present in high levels in purple-coloured fruits like blackberries.

When tomatoes were genetically modified they turned purple.

Agrobacterium tumefaciens

This is a bacterium which is used as a vector when scientists create some

[genetically-modified:An organism that has been

modified by humans through the introduction of useful genes from a different

species.] plants.

A common example is how scientists used Agrobacterium tumefaciens to make

herbicide-resistant crops. The process is as follows:

1. A crop plant with a natural [resistance: The opposition in an

electrical component to the flow of electricity through it. Resistance is

measured in ohms.] to a [herbicide:A chemical that killsunwanted plants.] is identified.

2. The specific [gene: The basic unit of genetic material inherited from

our parents. A gene is a section of DNA which controls part of a cell's

chemistry, particularly protein production.] (or genes) responsible for this

resistance is identified and cut out using [restriction

enzyme:An enzyme that cuts DNA at specific base sequences, which are

used in genetic modification.] .

3. The DNA is inserted into Agrobacterium tumefaciens which is then inserted

into the [embryo: The developing human offspring inside the

womb] of the crop plant.

4. These plants then grow into adult plants which are resistant to the herbicide

- so that when the fields are sprayed, only weeds are killed.

Bang Goes The Theory explains genetic modification of papaya plants


Flashinstalled.

Read on for higher

Bacillus thuringiensis - Higher tier

This [bacteria: Single-celled microorganisms, some of which are

pathogenic in humans, animals and plants. Singular is bacterium.] naturally

produces a [toxin:A type of natural poison produced by an organism,

often as a form of protection.] which is poisonous to many insects. The

[gene: The basic unit of genetic material inherited from our parents. A

gene is a section of DNA which controls part of a cell's chemistry, particularly

protein production.] for producing this poison has been inserted into crop plantswhich are now [resistant: Opposing something, or fighting against it.

Many strains of bacteria have become resistant to types of antibiotics, which

means that it is more difficult to kill them.] to these insect pests. However,

there are advantages and disadvantages to doing this.

The advantages of using this type of bacteria are:

Less insecticide has to be used

Crop yield is higher

The disadvantages of using this type of bacteria are:

The toxin could kill other, harmless insects

antioxidant

flavonoid

genetically-modified

resistance

herbicide

gene

restriction enzymes

embryos

bacteria

toxin

gene

resistant
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The Bacillus thuringiensis gene could be transferred into other wild plants

Some insect species have already evolved resistance to the toxin

The ethics of genetically modifying crops

Not all people agree with genetic modification. Some people think that there

might be long-term problems that scientists dont know about yet, or that genes

from genetically-modified crops might spread to other plants and make

superweeds.

Biofuels

A biofuel is a renewable fuel made from [sustainable:Activity

which does not use up or destroy resources or the environment, so that it can

continue to be done in the future.] sources such as animal or food waste, wood

and alcohol. Biofuels are a green alternative to [fossil fuel: Fuel,

such as coal, oil and natural gas, made from the remains of ancient plants and

animals.] . Common examples include using vegetable oil or alcohol in cars,

sometimes mixed with petrol.

A biodiesel refining plant in Motherwell

35,000 tonnes of old cooking oil and animal fat is filtered each year and

chemically converted into diesel fuel


Flashinstalled.

Biofuels are carbon neutral. This means that they only release as much carbondioxide when they are burnt as was used to make them originally by

photosynthesis. In this way, they dont increase the amount of carbon dioxide in

our atmosphere.

Some people worry that biofuels also have their drawbacks for instance, large

areas of land are used to grow some biofuels. This area of land might have been

forest before, but now cannot act as a carbon dioxide sink (a process whereby

carbon dioxide is removed from the atmosphere). Also, the land now cannot be

used by local people to produce their food.

More from Biotechnology

sustainable

fossil fuels

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31 Biotechnology _ Revision, Print

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