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GCSE Biology (OCR Gateway) > B6 - Beyond the Microscope > Flashcards

B6 - Beyond the Microscope Flashcards

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1
Q

Why can bacteria survive in a huge range of habitats?

A

They are capable of consuming a huge range of organic nutrients from their surroundings - this provides htem with energy.

Furthermore, some bacteria are capable of producing their own nutrients.

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2
Q

What are the four main shapes of bacteria?

A
  1. Spherical
  2. Rod
  3. Spiral
  4. Curved Rod
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3
Q

How do bacteria reproduce?

A

They reproduce through asexual reproduction (meaning they’re clones of eachother) through a process called binary fission. Binary fission is simply a process where the bacteria will split into two.

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4
Q

Describe the structure of a virus

A

Viruses have a protein coat that surrounds a strand of DNA.

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5
Q

How do viruses reproduce?

A
  1. Virus attaches itself to a specific host cell.
  2. Virus injects its genetic material into the cell.
  3. The virus then uses the host cell to make components of the new viruses.
  4. Eventually, this causes the host cell to split open and release new viruses.
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6
Q

How can the transmission of disease via food be prevented?

A
  1. Making sure food is probably cooked (to kill bacteria) before being eaten.
  2. Good hygiene (i.e. washing hands before eating).
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7
Q

How can the transmission of disease via water be prevented?

A
  1. Ensure that sewage is treated and disposed of.

2. Good sanitation (treating drinking water with chemicals)

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8
Q

How can the transmission of disease via human contact be prevented?

A
  1. Not walking around with bare feet.

2. Disinfecting surfaces.

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9
Q

How can the transmission of disease via airborne droplets be prevented?

A
  1. Sneezing into a tissue.
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10
Q

Describe the four main stages of an infection disease.

A
  1. The microorganism enters the body.
  2. The microorganism reproduces rapidly (the incubation period).
  3. Microorganisms produce toxins that damage cells.
  4. The toxins cause symptoms of an infection - for example, fever.
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11
Q

Why do natural disasters cause a rapid spread in diseases?

A
  • They damage sewer systems and clean water supplies.
  • They damage electrical supplies, meaning fridges stop working so food starts decaying.
  • People are moved out of their homes into densely packed camps.
  • Hospitals disrupted/destroyed.
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12
Q

Name the three main theories/discoveries that have contributed to our understanding of disease and how to treat it.

A
  • Scientist named Pasteur created the ‘germ theory of disease’
  • Scientist named Lister was the first to develop antiseptics.
  • Scientist named Fleming was first to discover penicillin (an antibiotic that kills bacteria in the body).
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13
Q

What two steps must doctors take to prevent bacteria developing resistance to antibiotics?

A
  1. Only prescribe antibiotics when absolutely necessary.
  2. Ensure that patients, if prescribed antibiotics, take all of the medicine given to them. Some patients stop taking the antibiotics as soon as they feel better, but this means resistant bacteria can emerge. This called ‘completing the dose’.
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14
Q

How do bacteria develop resistance to antibiotics?

A
  1. Antibiotics don’t cause resistance, but they create a situation where bacteria become resistant due to natural selection.
  2. Due to random gene mutations, bacteria with the ‘resistance’ gene are more likely to survive in bodies treated with antibiotics than bacteria without the gene.
  3. Therefore, that gene becomes more common in the gene pool because it is more likely to be passed onto offspring.
  4. Eventually, this might mean the bacteria species evolves completely to become resistant. This would be extremely dangerous, as we’d have no way of killing that type of bacteria once it enters our body.
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15
Q

Can we destroy viruses using antibiotics?

A

No.
This is because viruses inject their genetic material into cells that already exist in the body. Antibiotics only target specific bacterial cells.

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16
Q

What are the five main changes in the production of yogurt? List them in the correct order.

A
  1. Equipment is sterilised to kill unwanted microorganisms.
  2. Milk is pasteurised to kill bacteria and then cooled (must be cooled to create right conditions for added bacteria).
  3. A culture of bacteria (Lactobacillus) is added. The bacteria is incubated at a temperature of 40’c in a fermenter.
  4. A sample is taken to ensure milk has turned fully into yogurt.
  5. Flavors and colours added to yogurt.
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17
Q

During the production of yoghurt, what is the chemical role of the Lactobacillus bacteria?

A
  1. The bacteria breaks down the lactose in the milk.
  2. It respires anaerobically to produce lactic acid (the lactic acid is what makes the milk clot and solidify to make yogurt).
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18
Q

What is the balanced symbol equation for fermentation?

A

C6H12O6 → 2C2H5OH + 2CO2

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19
Q

What are the four main stages in the brewing of alcohol (via fermentation)?

A
  1. Sugar needs to be extracted from the source material (e.g. from barley or grapes).
  2. Yeast is added and incubated at a warm temperature. The yeast ferments the sugar into alcohol.

Note: The fermentation vessel is airtight to stop unwanted microorganisms entering and to stop oxygen from getting in (so the yeast will anaerobically respire).

  1. The beer and wine produced is drawn off through a tap.
  2. Beer is pasteurised to kill any yeast left in the beer and stop fermentation. Wine isn’t pasteurised, leaving any remaining yeast to pasteurise the sugar.
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20
Q

If beer was left unpasteurised, it would taste better. Why do most companies still decide to pasteurise beer?

A

Although not pasteurising beer would mean its taste would improve, there’s a risk that unpasteurised beer would spoil if not stored in the right conditions. Therefore, most companies pasteurise the beer to kill off remaining yeast.

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21
Q

What factor stops fermentation from going on forever?

A

As fermentation happens, the concentration of alcohol in the mixture increases. Eventually, the alcohol starts to kill the yeast. If the yeast population goes down, then the process of fermentation also slows down.

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22
Q

Why do we use different species of yeast to produce different strengths of alcohol?

A

Different species of yeast can tolerate different levels of alcohol. Only some specially adapted species of yeast are capable of producing strong wine or beer with a high concentration of alcohol.

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23
Q

Describe the process of distillation.

A

Distillation is used to create high-concentration alcohol by separating the pure alcohol from the alcohol-water mixture:

  1. Fermentation products heated up to 78’C. The alcohol (but not water) begins to boil and turn into vapour.
  2. The alcohol vapour rises and travels through a cooled tube. The alcohol condenses and is then collected.
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24
Q

Can you carry out distillation in your own home?

A

No, that would be illegal.

Distillation is a commercial process and can only be done on licensed premises.

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25
Q

Describe two different methods of transferring energy from biomass.

A
  1. Burning fast-growing trees (this process releases heat energy).
  2. Fermenting biomass to create biogas (which can then be used as a fuel).
26
Q

What are the three main advantages of biofuels?

A
  • Fossil fuels are running out, whereas we have lots of biomass available.
  • They do not cause an increase in greenhouse gasses.
  • They do not produce particulates (e.g. smoke/soot)
27
Q

What does biogas contain?

A
  • Mainly methane
  • Some carbon dioxide
  • Traces of hydrogen, nitrogen, and hydrogen sulfide.
28
Q

What two things must be true for biofuels not to cause a net increase in greenhouse gas levels?

A
  • They must be burnt at the rate new biomass is grown/produced.
  • Areas of land are not cleared of other vegetation in order to grow crops for biofuels.
29
Q

What are the two main disadvantages of biofuels?

A
  • Biogas doesn’t contain as much energy as the same volume of natural gas (a fossil fuel).
  • Large areas of land are often cleared for biofuel production. This means habitat loss, and can lead to the extinction of species.
30
Q

Why must biogas be produced to contain over 50% methane?

A
  • If biomass contains over 50% methane, it can be burnt in a safe and controlled way.
  • On the other hand, if biomass contains a much lower percentage of methane (e.g. 10%), it burns in a more explosive fashion.
31
Q

Describe the production of biofuels via fermentation.

A
  1. Plant waste and animal poo is put into a digester.
  2. Bacteria is put into the digester to break down the organic waste. This is done via anaerobic respiration.
  3. This process is done using a continuous flow method, meaning organic waste is continuously put into the digestor as the biogas and waste are removed at a steady rate.
32
Q

Why is biogas production affected by temperature?

A
  1. If the temperature is too cold, the bacteria don’t produce biogas as fast because they are respiring more slowly.
  2. If the temperature is too hot, the bacteria are killed.
33
Q

What is gasohol? Where might it be used?

A
  • It is a mixture of ethanol and petrol.
  • It is used in cars in countries like Brazil where they have lots of sugar cane (to produce biofuel) but not a lot of oil.
34
Q

Describe the difference between a sandy soil and a

clay soil in terms of particle size.

A

Sandy soils are made up of large mineral particles, whereas clay soils are made up of tiny particles.

35
Q

What is loam?

A

It is a soil that is a mixture of clay and sand particles.

36
Q

What do we call dead material in soil that has largely decomposed?

A

Humus

37
Q

Explain how particle size affects the air content and

permeability of soils.

A

If particles are larger, they form part of a soil that is more permeable and has a higher air content. This is because there are large pores (gaps) between the particles.

If particles are smaller, they are part of soil that is less permeable and with a lower air content. This is because their pores are smaller.

38
Q

How does aerating improve soils?

A
  1. Earthworms bury themselves inside soil, leaving burrows (creating more air gaps, AKA aeration).
  2. This provides organisms in the soil with more oxygen to respire and survive.
39
Q

How does draining improve soils?

A

By draining soil, you prevent it from becoming waterlogged - if soil becomes waterlogged, there’s less oxygen available.

40
Q

Explain why neutralising acidic soils and mixing up

soil layers is important.

A
  1. Neutralising acidic soils is important because acidic soils are less fertile.
  2. Mixing up soil layers is important to ensure that the nutrients are distributed evenly throughout the soil.
41
Q

Give four reasons why earthworms are important for soil structure and fertility.

A
  • They bury organic material for decomposition by bacteria.
  • They aerate and drain the soil
  • They mix up the soil layers
  • They neutralise acidic soil
42
Q

List four advantages of living in the water.

A
  • No problem of water shortages or dehydration
  • Less variation in temperature
  • More support
  • Easy disposal of waste products
43
Q

List two disadvantages of living in the water

A
  • More difficult to regulate water content

- Water provides more resistance to your movement

44
Q

Why must water organisms have a special mechanism for regulating water content?

A
  • If water can freely enter and leave the animal’s cells via osmosis, damage can be caused to the organism:
    1. For example, if the animal lived in salt-water, its cells would have a higher water concentration than the water outside (since that water also contains salt). Therefore, water would exit its cells and it would shrivel up and die.
    2. Or, if an animal lived in freshwater, the cells would swell and burst.
45
Q

How do amoebas use contractile vacuoles to regulate water content?

A
  • The contractile vacuole collects the water that diffuses in via osmosis.
  • The vacuole moves to the cell membrane and contracts to squeeze the water out of the cell.
46
Q

Why are whales most at risk of suffering health impacts due to pesticides such as DDT?

A

As you move up the food chain, the concentration of the pesticide within organisms increases.

This means whales are exposed to a large concentration of DDT, since they are consuming a large number of of organisms that already have DDT in their bodies.

This DDT often means whales will die.

47
Q

Name three enzymes used in washing powders and describe their uses.

A

Amylase - to digest carbohydrate starch

Lipase - to digest fat and therefore remove fatty stains

Protease - to digest protein and therefore remove protein stains

48
Q

Why do biological washing powders work better at moderate wash temperatures?

A

These are the optimum temperatures for enzyme activity. Any lower, and the enzymes won’t have enough energy to aid the reaction. Any higher, and the active site of the enzyme will denature (so the substrate will no longer ‘fit’ inside).

49
Q

Why do some stains wash out of clothing more easily than others?

A

Some stains are more soluble, meaning they will dissolve in water that can then be washed away.

50
Q

Why won’t biological washing powders work in acidic or alkaline tap water?

A

Enzymes are denatured at extremes of pH.

51
Q

How are foods sweetened using invertase?

A
  1. Invertase is an enzyme that converts sucrose into glucose and fructose.
  2. Those sugars are much sweeter than sucrose.
  3. Food can therefore be sweetened without adding extra sugar (good for low-calorie foods for people on diets)
52
Q

Explain why some people are lactose intolerant.

A
  1. They cannot produce the enzyme lactase
  2. Therefore, bacteria in the gut are able to ferment the lactose (since nothing is breaking it down).
  3. This fermentation produces products that lead to diarrhoea
53
Q

Describe how enzymes can be immobilised in gel

beads.

A
  • Enzyme is mixed with alginate

- The mixture is then put in a calcium chloride solution

54
Q

What are the main two advantages of immobilising enzymes?

A
  • The mixture isn’t contaminated with the enzyme.
  • immobilised enzymes in alginate beads can be
    used in continuous flow processing.
55
Q

How do we make lactose-free milk?

A
  1. We use immoblised lactase to convert lactose into glucose and galactose.
  2. People who are lactose intolerant will be able to absorb the glucose and galactose.
56
Q

Explain why genes from one organism can work in

another, making genetic engineering possible.

A

All genetic code is universal (all species have the same four DNA bases, just in different sequences).

57
Q

What are the six main stages of genetic engineering?

A

• identification of a desired gene in one organism
• removal of gene from DNA
• cutting open the DNA in another organism
• inserting the new gene into the DNA
• gene works in transgenic organism
• transgenic organism can be cloned to produce
identical copies.

58
Q

How are restriction enzymes used in genetic engineering?

A
  • Restriction enzymes cut open DNA to leave sticky ends.

- The ‘sticky ends’ allow ligase enzymes to rejoin the DNA strands.

59
Q

Describe how bacteria can be used in genetic

engineering to produce human insulin.

A

the gene for producing human insulin is cut out of
human DNA
• a loop of bacterial DNA is cut open
• the insulin gene is inserted into the loop
• the loop is inserted into a bacterium
• the bacteria are then able to produce insulin
• transgenic bacteria are cultured by cloning
• large quantities of insulin are harvested

60
Q

Why is bacterial DNA suited for genetic engineering?

A

It is made up of loops known as plasmids in the cytoplasm.

  • These plasmids are easily taken up by bacteria, so act as a ‘vector’ for transporting the DNA from one organism to another.
61
Q

After genetic engineering bacteria, what final step is carried out?

A

Special techniques known as ‘assaying’ can be used to check that the new gene is present in the bacteria.

62
Q

What are the four main stages in DNA fingerprinting?

A
  • extraction of DNA from sample
  • fragmentation of DNA using restriction enzymes
  • separation using electrophoresis
  • visualising pattern using a radioactive probe.

GCSE Biology (OCR Gateway) (6 decks)

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