The effect of nature of substrates on the rate of cellular respiration in yeast was determined by using the Smith fermentation tube method. Mixtures of 15ml distilled H2O, 10% yeast suspension and 15ml of the following solutions (all at 10% concentration):1- starch, 2 – lactose, 3 – sucrose, 4 – glucose, 5 – fructose, 6 – distilled water , were poured in six smith fermentation tubes. Cotton balls were plugged in the openings of the tubes and the tubes were kept upright and observed for 30 minutes. The mixture with the sucrose solution acquired the highest computed volume of gas evolved and the rate of CO2 evolution seconded by glucose and followed by fructose. This stated that the higher the amount of the CO2 evolved, the faster the rate of respiration. Mixtures with lactose, starch and dH2O solutions obtained zero result for the volume of gas evolved and rate of CO2 evolution. Thus, the nature of subtrate used slows down or fastens the rate of cellular respiration.
Cellular respiration is defined as an enzyme mediated process in which organic compounds such as glucose is broken down into simpler products with the release of energy (Duka, Diaz and Villa, 2009). It is a series of metabolic processes and oxidation-reduction reactions. Oxidation of substrates, such as glucose, is a fundamental part of cellular respiration (Mader, 2009). As a catabolic process, it may or may not require the presence of oxygen. The process that requires oxygen is called aerobic respiration while the process that does not require the presence of oxygen is called anaerobic respiration. (Duka, et.al. 2007)
Despite of its low yield of only two ATP (energy used by the cells to perform its duties), anaerobic respiration is essential because it continuously synthesizes ATP albeit oxygen is temporarily in short supply.
Although anaerobic respiration synthesizes a low yield of ATP (which is the energy used by the cell enables it to perform its duties), it is