GCSE Biology B6

  • Created by: Ruqayya11
  • Created on: 19-04-17 20:22
What features do bacterial cells have that allow them to survive?
A flagellum for movement. A cell wall to maintain shape and stop it from bursting. DNA to control the cell's activities and replication of the cell
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What different shapes can bacterial cells be?
Spherical, rod shaped, spiral or curved rods
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How do bacteria reproduce?
Splitting into two in a type of asexual reproduction called binary fission
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Why must all equipment be sterilised before bacteria reproducing on agar dish?
To prevent contamination by other microbes. This is called an aseptic technique
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How are bacteria successful?
Can survive on a different range of energy sources. Live in a wide range of habitats. Some bacteria can make their own food
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What does bacteria reproducing quickly mean?
This means that they can very rapidly spoil food or cause disease. This means that they must be handled carefully to avoid contamination of people, animal or food
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What is yeast?
Yeast is a sinlge-celled fungus that is grown for many functions
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How can yeasts growth rate be altered?
Changing food availability. Changing temperature. Changing pH. Removing waste products
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What are viruses?
Viruses are not living cells but very small structures made of a protein coat surrounding a strand of genetic material
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Under what conditions do viruses reproduce?
They only reproduce in other living cells. They only attack specific cells, which may be plant, bacterial or animal cells
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How does a virus reproduce?
It attaches itself to a specific hosts cell. Injects its genetic material into cell. Use the cell to make the components of new viruses. Causes the host cell to split open and die to release the viruses
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How can disease-causing microorganisms be passed on?
Spread in food- they can be prevented by correct food hygiene. Spread in water- can be prevented by correct water hygiene. Spread in airborne droplets- prevented by patient isolation
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What are the four stages in an infectious disease?
Microbe enters body. Reproduces many times causing symptoms- incubation period. Microbes cause the production of many toxins. Toxin causes symptoms, such as fever
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How can diseases occur in areas experiencing natural disasters?
Damage to sewage systems may lead to water supplies being contaminated. Damage to electrical supplies may stop refrigerators working-so food decays. Hospitals may be damaged or shortage of medical staff
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Why do doctors collect data on the incidence of various diseases?
To try and see patterns and make predictions
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What did Louis Pasteur do?
He helped to prove the germ theory of disease by realising that microbes from the air could make food go bad
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What did Joseph Lister do?
He invented the first antiseptic, using carbolic acid to prevent wounds becoming infected
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What did Sir Alexander Fleming do?
He discovered the first antibiotic, pencillin, which is produced from a fungus
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How have antiseptics been used to control disease?
Antiseptics are used on the outside of the body to kill microbes and prevent their entry
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How have antibiotics been used to control disease?
Antibiotics tend to be used inside the body to kill microbes once they have entered
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How do bacteria develop resistance to antibiotics?
The resistance appears in bacterium by a mutation. Because the bacteria can then survive and reproduce, the resistance by natural selection
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How do doctors prevent resistance spreading?
They only prescribe antibiotics when really necessary. They advise patients to always finish the dose so partially resistant bacteria are killed
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Explain the process of making yoghurt?
All equipment is sterilised. Milk is pasteurised by heating to 78*C. The milk is cooled down it is incubated with culture of bacteria. Sampling, adding flavours, colours and packaging
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What is the type of bacterium added to milk?
Lactobacillus. This causes the breakdown of lactose in milk to lactic acid, which makes the yoghurt taste acidic
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What does the process of fermentation involve?
Anaerobic respiration. Glucose -> ethanol + carbon dioxide
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Explain the process of brewing wine or beer?
Sugar is extracted by crushing grapes or barley grains. Yeast is added. Kept warm to ferment. Air and other microorganisms are kept out. It is allowed to clarify. Clear liquid is then removed from yeast sediment. Wine or beer are pasteurised- casked
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Consequences of the concentration of alcohol made by fermentation being limited?
So making drinks like whisky and brandy the process of distillation is used. This increases the alcohol concentration but is only allowed in licensed premises
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What happens when yeast is used in brewing?
It uses up all the oxygen in the container by respiring aerobically. This allows the number of cells to increase rapidly. Then conditions are kept anaerobically so alcohol is made
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What are the conditions affecting the rate yeast breaks down sugar?
Temperature and the presence or absence of oxygen
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Why is the process of pasteurisation used in brewing?
To kill harmful microbes. The liquid is kept at an elevated temperature. The temperature and time depends on the drink being brewed
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Why is the alcohol concentration produced by brewing limited?
This is because high concentrations of alcohol kills yeast cells, although some strains of yeast are more resistant to alcohol than others
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Examples of biofuels?
Fast-growing trees are grown and then the wood is burnt. Biomass such as sugar or waste material is fermented using bacteria or yeast and the product is used as fuel
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Why have biofuels become more popular?
They are alternative sources to fossil fuels, which are running out. They do not contribute to greenhouse gas levels. They do not release particulates when burnt
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What is meant by carbon neutral?
There is no net increase in greenhouse gas levels if biofuels are burnt at the same rate as biomass is being produced
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What problems occur if areas of land are cleared of other plants, to grow crops for biofuels?
Fuel may not be carbon neutral because the other plants cannot now remove carbon dioxide. Important habitats may be lost and species may become extinct
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What is biogas?
It is a fuel that contains: mainly methane, some carbon dioxide, small amounts of hydrogen, nitrogen and hydrogen sulfide
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How is biogas produced?
It can be produced on a large scale in a digester. This uses a continuous flow method as organic waste are constantly added and the gas and remaining solids are constantly removed
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Uses of biogas?
Is burnt to generate electricity. Is burnt to produce hot water and steam for heating systems. Is used as a fuel for vehicles
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How does biogas production increase?
Biogas production increases as temperature increases, up to about 45*C. Above this temperature production slows down
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How is biogas burnt in a controlled way?
Biogas containing more than 50% methane can be burnt in a controlled way, but about 10% can be explosive
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How is biogas production affected by temperature?
As temperature increases, the bacteria multiply faster and the enzymes within them work better. Above 45*C, the enzymes are denatured and the bacteria die
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How is gasohol produced?
Alcohol can be made by fermentation and is mixed with petrol to make gasohol. This is used to fuel cars in some countries
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What is gasohol made up of?
It is an ideal fuel where there is ample sugar cane but little oil. It is cheaper than importing oil
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What does soil contain?
Soil contains mineral particles of different sizes. In a sandy soil the particles are larger than in a clay soil
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What does loam contain?
A mixture of clay and sand. A large amount of partly decomposed animal and plant waste called humus
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How can humus content be found?
It can be found by burning off the humus using a Bunsen burner
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How can air content be found?
It can be found by seeing how much water is needed to fill air spaces
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How can water content be found?
It can be found by slowly heating the soil to evaporate the water
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What happens if soil has larger particles?
If soil has larger particles, then the air content and permeability is usually higher
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What happens if soil has large amounts of humus?
If soil has larger amounts of humus it will often hold more water and air
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What do many organisms that live in soil depend on?
They depend on a supply of oxygen for respiration and water for chemical reactions. There organisms form many food webs
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Why is humus in soil important to living organisms?
It decomposes to release minerals. It increases the air content of the soil
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Why are earthworms important to soil structure and fertility?
They bury organic material for decomposition by bacteria and fungi. They aerate and drain the soil. They mix up soil layers, They neutralise acid soil
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What do the aeration and draining produced by earthworm allow?
It allows organisms to respire aerobically
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Why is neutralising acid soils important?
It is important because some plants will not grow if the pH is too low and mixing up the soil layers is important so that dead material is decomposed
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What are the advantages of living in water
There is no risk of water shortage or dehydration. The temperature of water varies less than air temperature. Water provides support. Waste products are easily disposed in water
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What are the disadvantages of living in water?
The water content of the body can vary and needs to be controlled. Water is denser than air and so resists movement
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What is the impact of freshwater and salt water on organisms?
In freshwater, organisms take up too much water by osmosis. In salt water, organisms lose too much water to surroundings by osmosis
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What is amoeba?
An amoeba has a contractile vacuole that can store any excess water. The vacuole can then fuse with the cell membrane and empty the water to the outside
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What are phytoplankton and zooplankton?
Phytoplankton are tiny aquatic plants and zooplankton are tiny aquatic animals. Their numbers vary at different depths and seasons
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Why do they vary at different depths and seasons?
There will be less light in winter and deeper in the water. The temperature will be lower in winter and deeper in the water. Minerals are used up towards the end of summer
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What different sources of food do webs of marine organisms rely on?
Most rely directly on green plants. Others deeper in the ocean feed on dead material called marine snow that floats down. Some rely on bacteria deep in the ocean, acting as producers
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What causes eutrophication?
Sewage and fertiliser run off causes eutrophication
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What is eutrophication?
It involves the rapid growth of algae. which then all die and decay. This uses up oxygen, causing the death of animals because they're unable to respire
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Why are some species used as biological indicators?
This is because they are sensitive to pollution, so are used as indicators for pH and oxygen
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Why do chemicals, such as DDT and PCB, kill animals on the top of marine food chains?
This is because the chemicals are toxic. They do not break down quickly and so accumulate and become concentrated higher up the food chain. They affect animals with long lifespans- whales
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What enzymes do biological washing powders use?
Amylase- to digest carbohydrates such as starch. Lipase- to digest fat and remove fatty stains. Protease- to digest protein ad remove protein stains
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When do biological washing powder work best?
At moderate temperatures because this is the optimum temperature for enzymes to wokr
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What affect does the treatment with enzymes have?
The products of digestion are soluble and will easily wash out of the clothes
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Why might biological washing powders not work in acidic or alkaline tap water?
This is because this is not the optimum for the enzymes and they might start to denature
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How is sucrose broken down?
It can be broken down by the use of an enzyme called sucrase (invertase)
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What happens when sucrose is broken down?
The product is much sweeter, allowing the food industry to use less in food products
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What does invertase convert sucrose into?
Glucose and fructose. They are sweeter than sucrose, so less has to be added to the food, lowering the cost and the energy content
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How are enzymes immobilised in gel beads?
Mixing the enzyme with alginate. Dropping the mixture into calcium chloride solution
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Why are the immobilised enzymes produced very useful in reactions?
The mixture does not become contaminated with the enzyme. They can be used in continuous flow processing
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Why are some people lactose intolerant?
This is because they cannot produce the enzyme lactase. This means bacteria in the gut ferment lactose, which produces diarrhoea and wind
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How is milk treated for people who have lactose intolerance?
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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What does genetic engineering involve?
Genetic engineering involves transferring a gene from one organism to another. The organism receives the new gene called a transgenic organism
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What are the main stages in genetic engineering?
Removing desired gene from organism. Cutting open the DNA in another organism. Inserting new gene into the DNA. Ensuring the gene works in the transgenic organism
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How is the cutting and inserting of DNA achieved?
Using enzymes and often the transgenic organism can be cloned to produce identical copies
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What is used to cut open DNA?
Restriction enzymes are used. They leave several unpaired bases on the cut end. This acts as an 'sticky end'
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What joins DNA strands?
Lipase enzymes join DNA strands because the sticky ends on each cut section of DNA can be joined by complementary base pairing
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Why does the process of genetic engineering work?
It works because the genetic code is universal. This means that genes from one organism will produce the same protein in another organism
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How is bacteria used in genetic engineering to produce human insulin?
It involves cutting the gene for producing human insulin out of human DNA. Cutting open a loop of bacterial DNA. Inserting the insulin gene into the loop. Inserting the loop into a bacterium
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How are many copies of the bacteria cultured?
They are cultured by cloning and large quantities of insulin are harvested
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What are the loops of DNA used in this process called?
Plasmids. They are found in the cytoplasm of bacteria and because they can be taken up by bacteria, they can be used as vectors for genes
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Explain the assaying technique used to see if a bacterium has taken up a plasmid?
Scientists add genes that make the bacteria resistant to antibiotics. The bacteria are then flooded with the antibiotic by being grown on nutrient agar containing the agar. They then choose the bacteria that survive
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Identify the stages in the production of a DNA fingerprint?
Extracting DNA from a sample, such as blood. Cutting up the DNA using restriction enzymes. Separating the fragments using electrophoresis. Making the fragments visible using a radioactive probe
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Card 2


What different shapes can bacterial cells be?


Spherical, rod shaped, spiral or curved rods

Card 3


How do bacteria reproduce?


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Card 4


Why must all equipment be sterilised before bacteria reproducing on agar dish?


Preview of the front of card 4

Card 5


How are bacteria successful?


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