Mid Term Lab Report- Investigation of Carbon-dioxide (CO2) Production From Cellular Respiration in Yeast

Introduction There is a popular saying: giving a child sweets will make them “bounce off the walls”. This is simply due to the fact that sugar is being converted to energy, which children already have in abundance. Yet humans of all ages and all other living organisms obtain energy from cellular respiration (Phelan, p.134). Saccharomyces cerevisiae (yeast) cells can use glucose both by fermentation and aerobic respiration, but they prefer the less energy efficient fermentative method. This is due to the fact that glucose represses some genes that encode key respiratory enzymes (Maslanka, et al, p.1). In this lab experiment, I observed how yeast undergoes this anaerobic process. I inserted yeast solution into empty water bottles covered at the mouths by balloons and manipulated variables including sugar amounts and type and temperature in order to see how carbon dioxide is produced with differing circumstances. I then measured the results by recording the expansion of each balloon and new height of yeast in each bottle. To perform the experiment, I used a marker to label six empty half half-liter water bottles with respective numbers. I then poured two teaspoons of Fleischmann's Active Dry Yeast and a fourth cup of filtered water in all six bottles. I used a teaspoon of Florida Crystals Organic Raw Cane Sugar in bottles one through three, a third teaspoon in bottle four, no sugar in bottle five, and one teaspoon of Madhava Light Organic Agave nectar in bottle six. Agave nectar is a low glycemic fructooligosaccharide that is known as a natural, low calorie sugar substitute (Johnson). I replaced each bottle’s cap with a balloon, then taped the mouth of the balloons to the neck of the bottles to ensure they would remain secured. I measured the initial height of each yeast solution, at exactly two inches in all but bottle six, which was two and a third inches. Methods