Biology B3 Microorganisms.

Biology Unit 3 - Microorganisms and industry.

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What is the theory of biogenisis?


The theory that living things are created from other living organisms.



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What did Louis Pasteur do to prove the theory of biogenisis?


He heated two flasks, both left open to the air. One had a curved neck so that the bacteria in the air would settle in the loop and not get through to the broth. This flask stayed fresh proving it was the microbes and not the air causing it to go off.

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How is cheese made?

Culture of bacteria added to milk.
Bacteria produce curds in the milk
Curds seperated from the liquid Whey
More bacteria sometimes added and the whole thing is left to ripen
Moulds are added to give things like Blue Cheese it's colour and taste.

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How is Yoghurt made?

Milk is heat treated (KILL off any bacteria) then cooled.
Started culture of bacteria is then added.
The bacteria ferment the lactose sugar present in the milk to lactic acid.
The acid causes the milk to clot and solidify into yoghurt
Sterilised flavours can be added (e.g. fruit)

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What is yeast and what does it have (e.g. mitochondria)

It is a single-celled fungus which has a nucleus, cytoplasm, a vacuole and a cell membrane surrounded by a cell wall.

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What is the equation for fermentation of glucose by yeast?

Glucose ->  ethanol + carbon dioxide + energy

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What is equation for aerobic respiration?

Glucose + oxygen -> energycarbon dioxide + water

(easy way to remember is Going Out Every Christmas Holiday)

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How is beer made?

- Barley grains germinate. Amylase enzyme breaks down the starch into sugar. Grains dried in a kiln - this is called malting.

- Malted grain is mashed up and water is added - makes a sugary solution with lots of bits in it, this is then sieved to remove the bits.

- Hops added to give beer its bitter flavour.

- Sugary solution is then fermented by yeast, turning the sugar into alcohol.


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Awesome notes :) Thanks for the help

Star Pupils Tuition


Thanks :D

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