Biology Ia

Topics: Glucose, Carbon dioxide, Oxygen Pages: 3 (877 words) Published: June 13, 2013
Effect of Sucrose in the Anaerobic Cell Respiration in Yeast Cells Introduction:
The purpose of this investigation is to examine the effect of different levels of sucrose concentration on the rate of cellular respiration in yeast. Through the process of cellular respiration in yeast, gasoline is produced (through the production of ethanol), alcohol is produced (this occurs yeast breaks down the sugars in grain), wine is produced (when the sugars in fruits are broken down), and when making bread, yeast is relied on to break down the sugars in the flour. Yeast are small, unicellular fungi that depend on the sugars present in their environment to provide them with the energy that they require to grow and reproduce. Yeast are similar to bacteria in that they both grow on their source of food. They manufacture and release digestive proteins (enzymes) that break down the sugar molecules in their environment into monosaccharides that can be absorbed by the yeast and utilised as food (energy). Yeast are able to respire both aerobically and anaerobically (cellular respiration is when cells produce ATP by breaking down organic compounds). When oxygen is not present, yeast convert sugars into carbon dioxide and ethanol (alcohol). As they respire anaerobically, they produce ATP through the process of glycolysis (as it does not need oxygen). Glycolysis is the process in which one molecule or glucose is oxidised to two molecules of pyruvic acid. However, without the presence of oxygen, the yeast will rapidly be derived of NAD+ molecules which are essential in order for glycolysis to occur. This is when the yeast begin to undertake alcoholic fermentation, which is an anaerobic process in which pyruvic acid is converted into ethyl alcohol and CO2, in order to restore these molecules. This process also oxidises the NADH.

C6H12O6  2CO2 + 2C2H5OH, with 2 ATP also produced.

Yeast are capable of utilizing many different sources of carbon such as biopolymers, pentoses,...
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