Biology 3 - Microorganisms

2nd part of biology 3, micr organisms yeast anaerobic & aerobic respiration

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  • Created on: 08-05-10 12:34

Food and drink from Micro-organisms

Bio genesis: The theory that living things are created from other living organisms.

Before 1765 it was believed that substances in food were changed into microbes, which caused food to go off. In 1837 Theodor Schwann showed that meat, would not go off in air, provided that the air was heated first to kill microorganisms.

However in 1859, Louis Pasteur discovered thatit was the microbes not the air that caused food to go off.

Most Cheese is made using bacteria: Bacteria is added to milk, which produces solid curds in the milk, which are separated from the liquid whey. More bacteria is added to the curds ,and it is left to ripen.

Yoghurt is made using Bacteria as well: Milk is heated to get rid of the Bacteia. A starter culture of Bacteria is then added. The bacteria ferments the lactose sugar to lactic acid. The acid causes milk to solidify and turn into bacteria.

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Using Yeast

Yeast is a single celled Fungus, it has a nucleaus, cytoplasm, a vacuole, a cell membrane surrounded by a cell wall.

Yeast can respire with or without Oxygen.

Anaerobic respiration: Glucose ---> Ethanol + CO2 + Energy

Aerobic Respiration: Glucose + Oxygen ---> Carbon dioxide + Water + Energy

Yeast is also used to make Bread and Alcholic drinks.

During the making of Bread, Yeast converts sugars to CO2 and some Ethanol, The CO2 makes bread rise.

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