Yeast Respiration Lab Report

The purpose of this investigation is to test the effect of different sugar sources on yeast respiration.

Cellular respiration is the chemical process in which organic molecules, such as sugars, are broken down in the cell to produce utilizable energy in the form of ATP. ATP is the chemical used by all of the energy-consuming metabolic activities of the cell. In order to extract energy from these organic molecules, cellular respiration involves a network of metabolic pathways dedicated to this task.

Yeast is a fungus that can generate glucose into energy without using any oxygen molecules. We tested the fermenting ability of yeast from two different carbon sources: glucose and aspartame. We hypothesized that yeast is unable to use the carbon sources of aspartame. To do this, we decided to use both carbon sources in the same concentration. Each carbon source was mixed with the same amount of yeast solution. The experiment group of 5.5 mM aspartame solution was compared with the control group of 5.5mM glucose solution. We recorded the rate of fermentation for glucose and aspartame in the Vernier Lab Quest. The fermentation rate of aspartame is a negative number, and glucose is a positive number. Our results show that yeast was unable to ferment aspartame as yeast fermented glucose. The results indicate that aspartame has no effect on yeast fermentation rate because yeast do not catabolize aspartame because it does not have the appropriate enzymes to break it down.

Introduction: Cellular respiration and fermentation are used in cells to generate ATP. All cells in a living organism require energy or ATP to perform cellular tasks (Urry, Lisa A., et al. , pg. 162). Since energy can not be created (The first law of thermodynamics) just transformed, the cell must get its energy from an outside source (Urry, Lisa A., et al. , pg.162). “Totality of an organism’s chemical reactions is called metabolism” (Urry, Lisa A., et al., pg. 142). Cells get this energy through metabolic pathways, or metabolism. As it says in Campbell biology, “Metabolic pathways that release stored energy by breaking down complex molecules are called catabolic pathways” (Urry, Lisa A., et al. pg.

During this experiment, sugar sources were varied and respiration rate evaluated. To begin, a water bath was set at 30 degrees Celsius. This creates an optimum temperature for the enzymes in yeast to breakdown sugar and give off CO₂. Each sugar source, glucose, sucrose, lactose and glycerol were all added to its own unique yeast sample, one at a time. Each sugar source that was added to the yeast solution was immediately incubated for 10 min, then was transferred to a respiration chamber. The CO₂ sensor was put in, recording the CO₂ respiration for 4 min. This process was done for each sugar source. The reparation rate was recorded through Logger Pro. After 4 min passed, the slope was recorded, resulting in respiration rate.

To be able to carry on metabolic processes in the cell, cells need energy. The cells can obtain their energy in different ways but the most efficient way of harvesting stored food in the cell is through cellular respiration. Cellular respiration is a catabolic pathway, which breaks down large molecules to smaller molecules, produces an energy rich molecule known as ATP (Adenosine Triphosphate) and a waste product that is released as CO2.

This lab investigates the effects of Sucrose concentration on cell respiration in yeast. Yeast produces ethyl alcohol and CO2 as a byproduct of anaerobic cellular respiration, so we measured the rate of cellular respiration by the amount of CO2

The research question asks how varying sucrose concentrations affect the rate of anaerobic cell respiration in yeast, measured in CO2 production. The rate of anaerobic respiration will be determined by measuring the rate of CO2 production by the yeast cells.

The research question that was investigated was: How does the concentration of sucrose affect the rate of cellular respiration carried out by yeast? This experiment allows information to be collected on the rate of cellular respiration of yeast based on a solution’s sucrose concentration.

Since we obtain a p-value higher than 0.05, we accepted our null hypothesis that states, “there is no different between the different sugars utilize and higher population growth of yeast”. According to the scientific journal by fonseca, fructose should of yield a higher yeast concertation, since fructose can be directly incorporated into the glycolysis reaction. Fructose is a monosaccharide, so it doesn’t utilize energy to hydrolysis a reaction. On the other hand, galactose is a disaccharide which requires energy in order to be hydrolysis into a monosaccharides. The hydrolysis of galactose to a monosaccharide is tends to be a slow reaction.

Table 1: Table of Results Showing the Effect of Yeast Mass on the Rate of Yeast-Facilitated Fermentation of Glucose

Sugars are vital to all living organisms. The eukaryotic fungi, yeast, have the ability to use some, but not all sugars as a food source by metabolizing sugar in two ways, aerobically, with the aid of oxygen, or anaerobically, without oxygen. The decomposition reaction that takes place when yeast breaks down the hydrocarbon molecules is called cell respiration. As the aerobic respiration breaks down glucose to form viable ATP, oxygen gas is consumed and carbon dioxide is produced. This lab focuses on studying the rate of cellular respiration of saccharomyces cerevisiae, baker’s yeast, in an aerobic environment with glucose, sucrose, lactose, artificial sweetener, and water as a negative control. A CO2

The production of carbon dioxide in the yeast with lactose had a lower average than the average of yeast growing by it’s self. The lactose sugar effected the respiration the most. Its average growth was 3.896 and the plain yeast was 15.924; this makes the respiration rate 4 times smaller than the respiration rate of the plain yeast. The yeast highest point was 19.75, while the lactose only went up too 6.539; lactose is still 3 times smaller than yeast. Lactase was very harmful, while lactase and sucrose didn’t hurt as bad, but were not better than yeast. Lactase’s average respiration was about half of the yeast average respiration; while the average respiration of the sucrose in the almond milk was also about half of the average respiration in yeast. When looking at the smallest of the yeast and lactase you see the relationship of the lactase being half more clearly; the yeast smallest is 13.22, while the lactase’s is 6.07. Since 6 is half of 12, thirteen is

The small molecule foods allow the yeast to respire easily. The glucose should allow the yeast to respire more because it is already a small molecule sugar whereas the sucrose is a large molecule sugar this will mean that the yeast can use the glucose straight away without breaking it down, whereas with the sucrose it has to break it down into a simple sugar before it can use it this will take time

The approached used was to test the level of CO2 (mL) production, after different solutions with 1.5 mL of Saccharomyces cerevisiae and 4.5 mL and either 1M of glucose, fructose, or galactose go through cellular respiration. The higher level of CO2 produced indicates the more cellular respiration that took place. A