B6 - Beyond the Microscope

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Bacteria


Flagella - used for movement
Cell Wall - maintains shape and stop the bacteria from bursting
DNA - control cells activity and to replicate the cell

Bacteria can be all shapes - e.g. spherical, rod shaped, spiral

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Bacteria - 2

Bacteria reproduces by Binary Fusion which is a type of Asexual Reproduction. it involves the bacteria splitting into two.

Bacteria can be grown on agar. However all equipment must be sterilised to get rid of microbes before growth. This is called an aseptic technique.

Bacteria is very successful because...

  • they can survive on an enormous range of different energy sources
  • live in a wide range of habitats
  • some can make there own food, but majority take in organic nutrients

Bacteria can reproduce very quickly.
They can rapidly spoil food or cause disease.
Must be handled carefully to avoid contamination of people, animals or food. 

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Yeast

It is a single celled fungus that is grown for many functions.

Its growth rate can be changed by:

  • Changing food availability
  • Changing Temperature
  • Changing pH
  • Removing Waste Products

Growth rate of yeast doubles for every 10°C rise in temperature until optimum is reached.

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Viruses

Viruses are not living cells. They are in fact very small structures made of protein coat surrounding a strand of genetic material.

How can viruses reproduce?

  • Only can reproduce in other living cells
  • Only attack specific cells, which may be plant, bacteria or animal cells

When a virus reproduces it will...

  • attaches itself to a host cell
  • inject its genetic material into the cell
  • use the cell to make the components of new viruses
  • cause the host cell to split open and die to release viruses
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Viruses Reproduction

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Disease Transmission

Disease-causing microorganisms can be passed on in many ways.

Microbes can be spread in...

1. Food - e.g. Salmonella. They can be prevented by correct food hygiene
2. Water - e.g. Vibrio Cholera. They can be prevented by correct water treatment
3. Direct contact - They can be prevented by spreading barriers
4. Air - e.g. Influenza (flu). They can be prevented by people using tissue.

Diseases occuring in places that have experienced natural disasters this is because...

  • there is damage to the sewage system which could have led to water being contaminated
  • the could have been a electrical failure and fridges stop working so food decays
  • there is a large number of people moving out to get away, this means facilities can't cope
  • hospitals could have ben damaged or shortage of medical staff

Doctors take notes and data on the incidence of various dieseases (e.g. cholera, influenza) and to try and see patterns and make predictions. 

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Treatment of Disease

Many scientists have made many discoveries about how to prevent disease.

Louis Pasteur - Germ Theory (discovered microbes in air made food go bad)

Joseph Lister - Created Antiseptic (used carbolic acid to prevent wounds being infected)

Alexander Flemming - Created first Antibiotic (Penicillin - which was produced from a Fungus)

Since there discoveries, there findings have been adapted and are now used world wide

 - Antiseptic used on outside of the body to kill microbes and prevent their entry into body
 - Antibiotics tend to be used inside of body to kill microbes once they have entered
 - Antiseptics work on most microbes but antibiotics have no affect on viruses

Problems are occurring as bacteria are developing resistance to the treatment. Bacterium has a mutation which means it has a resistance this then reproduces and cant be stopped as it has a resistance = Natural Selections 

To stop antibiotic resistance spreading, doctors only prescribe when they really have to and make sure they always finish dose so partially resistance bacteria is killed.

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Yoghurt Making

To make yoghurt you use bacteria.

1. All equipment needs to be sterilised
2. The milk is then pasteurised by heating it to about 78°C
3. When the milk is cooled down it is incubated with a culture of bacteria
4. Followed by sampling and then adding flavours,colour and packaging 

The type of bacterium that is added to the milk is Lactobacillus. This causes the breakdown of lactose in milk to lactic acid, which makes the yoghurt turn taste slightly acidic.

The milk is cooled before adding the yeast otherwise it will be killed.

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Fermentation

Fermentation in yeast involves a anaerobic respiration.

Using this reaction, yeast can be used in brewing beer or wine:

  • Firstly sugar is extracted by crushing grapes (wine) or barley grains (beer)
  • Then yeast is added
  • It is kept warm to allow it to ferment. Microorganisms are kept out.
  • Beer or Wine is left to clear. The liquid is the removed from the yeast sediment.
  • It is then pasteurised and put into bottles

The concentration of Alcohol made by fermentation is limited. So to make brandy or whisky the liquid has to be distilled. This increases the alcohol concentration. 

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Fermentation - 2

The yeast used in brewing, uses up all the oxygen available by respiring aerobically, this allows the yeast cells to divide rapidly. The conditions are kept anaerobically so alcohol can be made.

Yeast break down sugar at different rates, in different conditions. Different conditions include the temperature and the absence/presence of oxygen.

Pasteurisation is used in brewing to kill all microbes. The liquid is kept at a raised temperature for a predetermined time. The time and temperature depends on the drink that is being brewed.

The alcohol concentration produced by brewing is limited, because high concentrations of alcohol kills yeast cells.

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Biofuels

A biofuel is a renewable energy source made from plants or manure.

There are several bio-fuels, they all use the energy that is trapped in biomass (Biomass is organic material which has stored sunlight in the form of chemical energy.).

 - Fast growing trees are cut down and the wood is used as fuel.
 - Biomass such as sugar or waste material is fermented using bacteria or yeast and the product is used as a fuel

Bio-fuels have become more popular because...
 - they are alternative sources to fossil fuels, which are running out
 - their waste makes no increase in greenhouse gas levels
 - they dont release particulates when they are burnt

There is no increase in greenhouse gas levels if the bio-fuels are burnt at the same rate that biomass is being produced.

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Biofuels - Problems

However, problems can occur when areas of plants and green land is removed for growth of bio-fuels crops.

If plants are removed then they can not take in carbon dioxide so this means the fuels may not be carbon neutral

Important habitats may be lost and species may become extinct.

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Biogas

Biogas is a fuel that consists of mainly methane, some carbon dioxide and very small amounts of hydrogen, nitrogen and hydrogen sulfide.

Bio-gas can be produced on a large scale in a digester. This involves a continuous flow of organic waste are constantly added. The gas and remaining solids are constantly removed.

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What is Biogas used for?

The bio-gas which is produced is:

  • burnt to generate electricity
  • burnt to produce hot water and steam for heating systems
  • used as a fuel for vehicles
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Biogas - 2

Biogas production increases as temperature increases, up to about 45°C.

When it goes above 45°C production slows down.

This is because as the temperature increases the bacteria multiplies faster and the enzymes work with them better. Howver when it gets above 45°C the enzymes denature and the bacteria dies.

Biogas contains more than 50% methane, which can be burnt in a controlled way, but only about 10% is explosive.

Biogas is a cleaner fuel than diesel and petrol but it doesnt have as much enrgy as them.

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Gasohol

Alcohol can be made by fermentation. This can be then mixed with petrol to make gasohol. This is used instead of petrol in countries such as Brazil.

Gasohol is an ideal fuel in countries where there is a lot of sugar canes but little oil. It is cheaper than importing oil. 

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Components of Soil

Soil contains mineral particles of different sizes.

In a sandy soil, the particles are smaller than in clay soil.

Loam
Loam is a soil that contains a mixture of clay and sand and also a large amount of humus (partly decomposed animal and plant waste.)

Humus content can be found by burning off the humus using a bunsen burner

Air content can be found by seeing how much water is needed to fill the air spaces

Water content can be found by slowly heating the soil to evaporate the water

If the soil has large particles - air content and permeability = usually high

If the soil has large amount of humus = hold more water and air

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Living in Soil

Many organisms live in soil and depend on a supply of oxygen for respiration's and water for chemical reactions.

Humus in the soil is important to the living organisms as it will:

  • decompose to release minerals
  • increase the air content in the soil

Earthworms are also important to soil structure and fertility because they:

  • bury organic material for decomposition by bacteria and fungi
  • aerate (introduce air) and drain the soil
  • Mix up soil layers
  • Neutralise acid soil

The aeration and draining of the soil allows organisms to respire aerobically
Neutralising soils is important because some plant wont grow if the pH is too low 
Mixing up soil levels is important as it allow dead material to be composed 

Charles Darwin found out the earthworms role in the soil.

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Living in Water

Advantages:

  • No risk of water shortage or dehydration
  • Temperature varies less
  • Water helps provide support
  • Waste products are easily disposed of into the water

Disadvantages:

  • Water content of the body can vary and needs to be controlled
  • Water is denser than air, resists movement
  • Freshwater - too much water may be taken up by osmosis
  • Saltwater - too much water may be lost to the surroundings by osmosis

Organisms such as amoeba have a contractile vacuole that can store any excess water. 
The vacuole can then fuse with the cell membrane and empty the water. 

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Phytoplankton and Zooplankton

Phytoplankton = tiny aquatic plants
Zooplankton = tiny aquatic animals

The number of phytoplankton vaires due to the factors that limit and increase photosynthesis:

 - Less light in winter
 - Lower temperatures in winter
 - Minerals are used up towards the end of summer

Zooplankton relies on its food from its food webs to get food.

 - Most rely on green plants
 - Others deeper in the ocean feed on dead mineral snow that floats down
 - some rely on bacteria, deep in the ocean, acting as producers 

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Water Pollution

Sewage and Fertilisers running off into rivers can cause a process called eutrophication to occur.

This involves the chemicals running into rivers which causes algae to grow, which dies and decays. This uses up the oxygen, causing the death of animals because they are unable to respire.

Some species of organisms are more sensitive to pollution than others and so they can be used as biological indicators for pH and Oxygen.

Chemicals such as PCBs and DDT can kill animals at the top of marine food chains. This is because the chemicals are:

  • Toxic
  • Do not break down quickly, they group and increase in concentration higher up in the food chain
  • Affect animals with a long life span e.g. Whales
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Enzymes in washing powders

Biological washing powders use enzyme such as:

Amylase - to digest carbohydrates (starch)
Lipase - to digest fats and oils (fatty stains)
Protease - to digest proteins (protein stains)

Biological washing powders work best at moderate temperatures because this is when enzymes work best. Too high and they denature.

After treatment with enzymes, the products of digestion are soluble and so will easily wash out of the clothes

Biological washing powders may not work in slightly acidic and alkaline tap water because this isn't optimum for the enzymes and they may start to denature.

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Enzyme and Sweetners

Sucrose can be broken down by the the enzyme sucrase (invertase)

Sucrose is broken down by invertase into glucose and fructose
Both of which are sweeter than sucrose, so less has to be added, lowering the cost and energy content

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Lactase and Immobilised Enzymes

Enzymes can be immobilised in gel beads by:

 - mixing the enzyme with alginate
 - dropping the mixture into calcium chloride solution 

The immobilised enzymes produced are very useful in reactions. This is because...

  • the mixture does not become contaminated with the enzyme 
  • they can be used in continuous flowing process

Some people and animals are lactose intolerant because they cannot produce lactase (enzyme). This means that bacteria in the gut ferment lactose, which produce diarrhoea and wind.

Milk can be treated for people who have lactose intolerant:

 - Immobilised lactase is used to convert lactose in milk into glucose and galactose
 - Glucose and galactose can then be absorbed from the milk with no side effects 

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Genetic Engineeing

Genetic engineering involves transferring a gene from one organism to another.
The organism that recieves the new gene is called a transgenic organism.

Main Stage Of Genetic Engineering

1. Identifying and removing a desired gene from one organisms
2. Cutting open the DNA in the desired organism
3. Inserting the new gene into the DNA
4. Make sure the gene works in the transgenic organism 

The cutting and inserting of DNA is achieved using enzymes and often the transgenic organism can be cloned to produce identical copies

The process of genetic engineering work because the genetic code is universal. This means that genes from one organism will produce the same protein in another.

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Restriction Enzymes, Sticky Ends and Ligase

Restriction Enzyme = cut open the DNA, they cut it so they leave unpaired bases at the ends

Sticky Ends = the single strand of unpaired base, this is where the DNA from the other organism fits

Ligase = Sticks the DNA together once the other DNA is paired and fitted

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Genetically Engineeing Bacteria

Bacteria can be used in genetic engineering to produce human insulin. This involves:

  • Cutting the gene for producing human insulin out of human DNA
  • Cutting open a loop of bacteria DNA
  • Inserting the insulin gene into the loop
  • Inserting the loop into the bacterium

Many copies of the the bacteria are cultured by cloning and large quantities of insulin are harvested

The loops of DNA used in this process are called plasmids. Plasmids are found in the cytoplasm of bacteria. They can be used as vectors for genes because they can be taken up by bacteria.

To find out if a bacterium has taken up a plasmid an assaying technique is used:

 - Scientists add genes to make the bacteria resistant to antibiotics
 - The bacteria are the flooded with the antibiotic by being grown on nutrient agar containing the antibiotic
 - Scientists then choose the bacteria which survive 

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Genetically Engineering Bacteria - 2

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Genetically Engineering Bacteria - 2

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DNA Fingerprints

DNA fingerprints are used to identify individuals. They can be stored to help police alienate people who commit crimes.

Some people are worried that  they are also used for other reasons. Such as assesing the likelihood of a person developing a disease.
The information could be used as a reason to withold life insurance.

How to collect a DNA Fingerprint:

  • Extracting DNA from a sample (this is usually blood)
  • Cutting up or fragmenting the DNA using restritcition enzymes
  • Seperating the fragments using electrophoresis
  • Making the fragments visible using a radioactive probe. 
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DNA Fingerprints

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