Biology 3 Part 2 Basics- Microorganisms + their uses

These cards include all the basics you need to know for the second part of the AQA biology, triple science part 2 (B3.13-B3.21)

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  • Created by: Rachel
  • Created on: 05-05-08 13:37

B3.13- Growing Micro organisms

Bacteria and fungi need nutrients to survive

  • Carbs, like starch/glucose, provide energy
  • Mineral ions/urea provide nitrogen for the synthesis of proteins


  • A growth culture medium with provides the needed nutrients to microorganisms
  • melts @ 98 degrees C, when it can be poured into petri dishes. It is solid @ 44 degrees C.
  • Microbes do not digest or use up agar jelly

School lab temp limit=25 degrees C to stop pathogens growing

In industry, temperature higher than 30 degrees C are often used to speed up the growth rate and increase the yield.

Whole colonies of microorganisms can be produced by bacterium divided and multiplying.

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B3.14- Aseptic Technique

-Prevents harmful microbes from contaminating a culture


  • Sterilized in AUTOCLAVE
  • Pressurized steam at 121 degrees C for 15 mins


  • Ultraviolet
  • Ionising radiation
  • Hands must be washed
  • Hair tied back
  • Broken skin covered
  • Working surfaces msut be clean and cleared
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B3.14- Aseptic Technique (Continued)

  1. A McCartney bottle of agar jelly is poured into a Petri Dish (which has been prepared using autoclave previously)
  2. The innoculating loop is sterilized by placing it in the flame of a Bunsen burner
  3. When the loop is cool , microbes from the pure culture are collected on the loop
  4. Holding the Petri dish at an angle, the loop is swept across the agar jelly, depositing the microbes
  5. The dish is then sealed to prevent contamination and the detail written on the base
  6. Once the results have been recorded, the culture is autoclaved

A Bunsen Flame is usually present throughout all of this, causing an updraught, minimizing the risk of contamination via air.

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B3.15- Biogenisis

ABIOGENISIS/SPONTANEOUS GENERATION= the idea that organisms could come into existence from non living material


  • Did not believe in spontaneous generation
  • Knew that boiling killed micro organisms
  • Boiled a chicken broth, covered it so no air came in and found that no bacteria grew after
  • Therefore spontaneous generation does not occur
  • Some said this only proved abiogenisis does not occur without air


  • All living organisms are made up of one or more cells
  • Cells are the building blocks of life- "units of structure and foundation"
  • Cells occur from pre existing cells' division
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B3.15- Biogenisis (continued)


  • Devised swan neck glass that let air in but stopped microbes
  • Boiled broth and put it in glass- it stayed fresh (no microbes grew)
  • He concluded that there was no "life force" in the air, as was believed by many, and therefore spontaneous generation did not exist

BIOGENISIS= living organisms produce other living organisms

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B3.16- Yoghurt and Cheese

  • Cultures of bacteria are used for fermentation (named STARTERS)
  • milk is incubated at 40-60 degrees C for 6 hrs during this process


  • The sugar in milk, used by bacteria for energy
  • Fermented (anaerobic) to make lactic acid
  • This acid lowers the Ph, making the milk clot or solidify in parts (forming yogurt)

LIVE YOGHURT- contains living bacteria

PROBIOTIC YOGHURT- contains bacteria from the intestine that can be helpful after diarrhoea

RENNIN- milk clotting enzyme used along with bacteria to produce lactic acid in order to curdle or sour milk

CURDS=white solids, can be pressed into containers to form cheese

WHEY=watery liquid part

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B3.17- Yeast

To be continued...

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