gcse science biology unit B6 cards

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  • Created by: charlie
  • Created on: 07-06-13 15:54


bacteria cells:

  • smaller + simplier- cell wall to keep their shape + stop them from bursting 
  • strand of DNAcytoplasm- control cell activity+ replication- several small DNA loops(plasmids)
  • flagellum helps movement 
  • come in 4 shapes: rods, curved rods, spheres, spirals 
  • bacteria consume organic nutrients from surroundings+produce own nutrients- energy

asexual reproduction 

  • clones of eachother- reproduce by binary fission- split in two 
  • quickly+ faster when warmer + nutrients 

aseptic technique to culture bacteria on agar plate-gloves, sterilise equipment, sealing dish, disposing of culture safely after 

bacteria can make useful things... yoghurt:

  • equipment sterilised-milk pateurised-cooled-lactobacillus bacteria added-icubated in fermenter vessel-break down lactose sugar into lactic acid-milk clots+solidifies-yoghurt-flvours+colours added-pakaged 
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viruses can ony reproduce inside living cells:

  • viruses (protein coat around strand of genetic material)
  • can only reproduce inside living cells- infect organisms to multiply 
  • infect plant, animal, bacteria cells but only particular type will attack specific cells 

how it reproduces: attaches to host-- inserts genetic material--uses host cell to make components--host splits open--releases virus 

different ways diseases are transmitted:

  • in food- food poisoning 
  • in water- chloera 
  • by airborne droplets- influenza- coughing/sneezing 
  • through contact- athletes foot- fungus 
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treating infectious diseases

four stages: 1)-microorganism enters body 2)-reproduces rapidly 3)-produces toxins damaging cells+tissues 4)-toxins cause symptoms (between exposure+symptoms incubation period)

antiseptics+antibiotics help control diseases

  • antiseptics outside body- clean wounds+surfaces- prevent infection 
  • antibiotics inside body- only kill bacteria 

resistant bacteria- random mutations- changes in bacterias characteristics- less affected- better able to survive+reproduce- gene passed on (natural selection)

  • finish bacteria course- so kill all bacteria- not just stop when feeling better
  • only take prescribed antibiotics

history of improved disease treatment 

  • Louis Pasteur- germ theory 1857- microbes in air that cause disease+decomposition
  • Joseph Lister- antiseptics 1860's-stopping sepsis- used carbolic acid to dress wounds 
  • Alexander Flemming- penicillin 1928- by accident found agar plate+no bacteria round mould
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respires anaerobically only by fermentation:

  • glucose=ethanol+carbon dioxide 

when yeast respire aerobically- more energy- producing a fruit vinegar 

yeast growth rates depend on conditions 

  • optimum temp- growth rate doubles for every 10d.c, above denatures 
  • more food (glucose)- keeps on inc. 
  • more toxic waste products (ethanol)- slowly then rapidly dec.
  • optimum pH- below too slow, above too slow 

measured by how much glucose it breaks down- faster yeast produces the more glucose broken

wastewater cleaned up with yeast:

  • food-processing factories need to get rid of sugary water- 
  • yeast uses up sugar in respiration- if dumped in lake bacteria would mass produce use up O2
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  • beer made from grain(barley), germinate for few days, starch in grains broken down into sugar by enzymes, grains dried in kiln(malting), mashed up+water added for sugary solution, hops added to give beer bitter flavour 
  • wine made from grapes- mashed, water added 


  • yeast added +mixture incubated(kept warm), yeast ferments, alcohol concen. inc. slowly killing yeast as fermentation slows, diff. species tolerate diff. levels 


  • beer+wine produced is drawn through tap- clarifying agent(chemicals) added for clarity 


  • beer is pasteurised(heated to kill any yeast)
  • wine isnt(improves taste of wine, as fermentation continues)

distillation improves alcohol content- separate alcohol from alcohol-water solution, fermentation products heated to 78d.c alcohol boils water doesnt, alcohol rises, condensed, into collecting vessel- is a licensed process 

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energy transferred from biomass:

  • living or recently dead organic material-store of energy (trees burnt, biomass fermented-biogas)


  • 70% CH4, 30% CO2, (over 50% CH4 burns easily, 10% explosive)
  • used as fuel- turn turbines, for electricity, burned to heat water (houses), fuel in transport

made by anaerobic fermentation of waste material: plant waste--digester(fermenter)--different types of bacteria added--decompose chains--util biogas produced (fermentation without O2)

biofuels advantages:

  • sustainable- crops replaced, carbon neutral, cleaner than diesel/petrol(no particulates)


  • doesnt contain as much energy as same vol. of natural gas, clears large areas(habitat loss+extinction)

ethanol used as biofuel: cleaner fuel, renewable (fermenting glucose), mixtures gasohol (10% ethanol, 90% petrol)- Brazil use as lots of sugar cane not much oil

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diff. soils contain diff. particulates 

  • sandy soils: large min. particles, large pores (high air content+very permeable)
  • clay soils: tiny particles, very small pores (low air content+low permeability)
  • loam soils: mixture of sand+clay (properties depend on relative amounts)
  • all soils: humus (decomposed dead organic matter)- supports soil life 

experiments to work out structure of soil sample:

  • water+humus content: mass--heat to 105d.c-- constant mass+water boiled off-- take mass (water)-- heat to 550d.c 2 hours-- burns off humus---measure difference (humus)
  • air content: loosely packed soil--take vol.--add water via pipette till full-- measure how much water added(same as vol. of air)

soil full of living things 

  • layers: 1st)herbivores(slugs,snail) 2nd)carnivores (ground beetle,spider) 3rd)detritivores(earthworm+millipede)
  • soil needs water+O2+humus(releases min.+nutrients used by others- increases air content allowing more O2)
  • earthwroms help soil: CHARLES DARWIN: good for soil structure+fertility as the 1)bury leaves to be decomposed  2)burrows allow aeration+water drain through allowing more O2 3)mix up layers+nutrients disribution 4)poo neutralises soil acidity - so soil more fertile 
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life in water

advantages: less variation in temp, provides support, waste disposal easily disperses 

disadvantages: need more energy due to resistance, water regulation- nothing is done on solutes+osmosis e.g living in salt-water water would want to leave to even up- causing shrivel

amoebas regulate water content using contracting vacuoles:  single celled- contracting vacuole collects water that diffuses in by osmosis- moves to cell membrane+contracts to empty water 

plankton microscopic organisms: phytoplankton+zooplankton (important as main producers):   population size varies according to season:  increase between late spring+late summer (algae bloom)- more light for photosynthesis, temps inc. for energy, zoopla. inc. more phtopla. to feed on 

diff. types of food webs:

  • 'grazing food webs' - begin with living producer 
  • deep water- grazing food webs supported by bacterial producers rely on sulphur, or feed on dead , decomposing material 'marine snow'

causes of water pollution:

  • eutrophication- fetilisers add nutrients-algae grow-alage die-bacteria feed-use up O2-animals die 
  • industrial chemical pesticides- arent broken down+concen. inc. up the food chain 
  • idicator species determine pollution level- clean(stonefly nymph) dirty (sludgeworm)
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enzymes in action

  • biological washing powder- enzymes which break down stubborn stains 
  • non-biological washing powder- chemicals which break up stains- products are soluble in water- work best in moderate temps, non-extreme pH such as acidic or alkaline tap water
  • special stain removers- just concentrated specific enzyme for the stain 
  • medical products- diabetes: doctors taste--benedicts(heated changes from blue to orange in presence of sugar)--regent strips(enzymes dipped in urine+change colour)
  • based on sequence of enzyme reactions 
  • food industy - low calorie food- sucrase breaks down sucrose to glucos+fructose much sweeter than sucrose(table sugar) same sweetness less sugar---cheese rennet clots milk in---pectinase breaks down pectin so fruit cells release fruit juice 
  • immobilised enzymes easier to remove - encapsulate in alginate beads (mixing alginate+dropping mixture in calcium chloride solution)- dont contaminate product, used continuous process 
  • make lactose free milk- immoblised lactase breaks down lactose into glucose+galactose (simple sugars which can be absorbed by someone whos lactose intolerant)
  • used in reagent strips- quick+convenient- drop of blood added+ changes colour depending of glucose concen. 
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genetic engineering

  • altering genetic code- tansfer genes becasue code in universal 
  • gm organism called transgenic organism 

 main steps 

  • identify wanted gene 
  • remove gene from organisms DNA
  • cut open DNA you want to put gene into + insert it
  • host is now transgenic+ can make copies 

e.g bacteria 

  • human insulin- bacteria- bacteria makes human insulin- reproduce-millions of insulin producing bacteria 
  • identify gene--remove using sticky enzymes--leaves DNA with 'sticky ends'---loop of bacteria DNA plasmid prepared using restricting ezymes to cut open---insulin inserted---sticky ends allow enzyme ligase to join DNA strands together 
  • plasmid known as vector (carries gene into another organism)
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DNA Fingerprinting

  • DNA unique used in forensic science+paternity tests 
  • some want everyones fingerprint stored on database- big invasion of privacy, how safe?

how it works 

  • extract DNA from cells 
  • restriction enzymes cut DNA into fragments- where recognised as particular order of bases
  • sections diff. for everyone 
  • DNA section lots of times will be cut into little bits- if few times left to big bits 
  • DNA bits separated out by electophoresis- fragments suspended in gel, electrical current passed through
  • DNA negatively charge so moves to positive anode- smaller bits move faster 
  • DNA tagged with radioactive probe- placed on photographic film- goes dark where radioactivity is revealing DNA fragment positions 
  • look where DNA fragments ended up to identify matches 
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