AQA Biology B3.3

Set 1

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How can we grow simple microbes in a lab?

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Simple microbes can be grown in the lab, by culturing, this normally happens in a culture medium, which is often agar gel. 

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 Why must safety precautions be taken when doing this?

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When growing microbes in a lab, everything must be done very carefully so as not to mutate the microbes, when microbes are cultured in a school lab they petri dishes must not be heated over 27 degrees, to prevent the spread of pathogenic microbes. 

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What does fermentation mean?

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Fermentation is the anaerobic conversion of sugar to carbon dioxide or alcohol by yeast.

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     Explain the function of yeast in bread production.

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In bread product, the yeast grows and respires – producing carbon dioxide, this makes the bread rise.

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Describe the process of beer production.

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Making beer requires a process called malting, where barley grains are soaking in water to keep them warm. Germination begins and enzymes break down the starch in the grains into a sugary solution. This solution is extracted and used as an energy source for the yeast. The yeast and sugar mixture is fermented to produce alcohol, and then hops are often added to give the drink flavour. The beer is then left to settle, clear and develop fully its flavour.

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Describe the process of wine production.

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Making wines uses the natural sugars found in fruit, for the yeast’s energy source. The fruit is pressed for its juice, which is then mixed with yeast and water. The yeast is left to respire anaerobically, until all of the sugar is used up. The wine is then filters to remove the yeast, and stored in bottles, to mature.

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How is yoghurt made?

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Yoghurt is made by the bacteria  action on the lactose, you can be made by adding a culture of the right type of bacteria to whole milk; keeping the mixture warm so the bacteria grow, reproduce and ferment; bacteria break down the lactose, so lactic acid is produced – this is called lactic fermentation; lactic acids causes the milk to clot and solidify to form yoghurt, further bacterial action gives yoghurt a creamy texture.

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How is cheese made?

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Cheese making depends on the bacterial action in milks, bacteria is added to the milk, bacteria converts lactose into lots lactic acid, this makes the solid parts (curds) completely soli, enzymes are added to separate the curds and whey. Then another bacteria and moulds is added to the curds and it is left to dry out. The cheese is then left to ripen. 

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Name the equipment used to industrially produce microbes.

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What features do these have to help grow microbes well?

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An oxygen supply, for the microbes to use in respiration; a stirrer to keep the microbes in suspension and to maintain temperature, ensure food and oxygen is supplied equally; a water-cooled jacket, to remove excess heat; and pH and temperature measurer so changes can be made if necessary.

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