Lab Report on Cellular Respiration and Fermentation

Introduction

When living under aerobic or anaerobic conditions, organisms can utilize different metabolic pathways, especially glucose metabolism. In cells, aerobic respiration provides up to 38 ATP per molecule of glucose. Another form that does not produce large amounts of ATP is called anaerobic respiration, which allows glycolysis to continue and restores oxidative capacity in the form of NAD+ (Malinoski, Biological Principles I Laboratory Manual, 2019, P. 64). Three experiments were conducted in this laboratory to study two forms of cellular respiration.

Part 1: Aerobic Respiration

DCPIP can protect the loss of FADH2(enzyme), because it has higher electron affinity.

The more FADH2 get produced, the more DCPIP get reduced, the color of the solution becomes clearer or less blue. As %T goes up, it means that more DCPIP has been reduced. For better quantified results, a spectrophotometer was used. Spectrophotometer can monitor % transmittance from continuous assay.

Hypothesis:

A. If there is only mitochondrial suspension, but no DCPIP in the tube, the percent transmittance will maintain at a high point.

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B. If there is only DCPIP, but no mitochondrial suspension in the tube, the percent transmittance will maintain at a low amount.

C. If there is more succinate in the tube, the trends in percent transmittance will be increased.

Materials and Procedures:

Followed the Laboratory Manual. (Malinoski, Principles of Biology I Laboratory manuals, 2019, pp. 66-68)

Results:

The percent transmittance of the solution in tube 2 only increased a small amount as time went by and did not become clearer apparently. The solution in tube 3 and 4 became clearer, and tube 4, which contains a higher volume of succinate with the same concentration of mitochondria and DCPIP, became clearer faster than tube 3, and the increment of % transmittance is larger than tube 3 too.

% transmittance of Tube 5, which did not contain mitochondria, only decreased a small amount as time goes and did not become clearer.

Discussion:

The hypothesis was supported by the data and graph. The % T in the first tube and the fifth tube maintained 100 and around 34, no matter what the time is. It supported the first two hypotheses, that without either DCPIP or mitochondrial suspension would have no trends in percent transmittance. The other three tubes supported the third hypothesis, that more enzymes occurred in the tube; the higher trends in percent transmittance. DCPIP blocked the loss of the enzyme, so more DCPIP was in the tube; more pure and higher trends in percent transmittance were in the tube. The data was reliable by following the instructions from the Lab manual; however, there was some error existing during the lab. The percent transmittance in the fifth tube should maintain a certain number. When the tube was put in the spectrophotometer, the outside of the tube was not wiped. This might cause the various number of the %T to observe.

Part 2: Fermentation by Baking Yeast

Enzymes require a particular substrate and environmental conditions such as pH, concentration, and temperature. When the temperature is too high or too low, the enzyme will be broken, so there will be less reaction. When the temperature is sub-optimal, there is part of enzymes are used; the reaction will have low efficiency. When the temperature is optimal, most of enzymes can be used; the reaction will have high efficiency. There are six types of sugar, glucose, maltose, fructose, sucrose, galactose, and lactose. In these six types, galactose cannot break down by the enzyme, and lactose is made of glucose and galactose. Therefore, there will be little reaction occurs with galactose and lactose. In this part, carbon dioxide production is an indicator of anaerobic respiration. The experiments were carried out under two different conditions: incubation temperature and alternate sugar source. The aim is to study the effect of temperature on yeast viability and what carbohydrates yeast can utilize.

Hypothesis A:

If the temperature rises, the amount of carbon dioxide produced increases; if the temperature reaches the limit, the amount of carbon dioxide produced decreases.

Hypothesis B:

If vial contains lactose, then no carbon dioxide will be produced; if lactase is added, carbon dioxide will be produced.

Materials and Procedures:

Followed the Laboratory Manual. (Malinoski, Principles of Biology I Laboratory Manual, 2019, pp. 72-74)

Results:

A: For Tube 1 (0ºC), 0.5 ml of CO2 was produced. In tube 2 (room temperature, 22.8ºC), 0.8 ml of CO2 was produced. In tube 3 (45ºC), 4.5ml of CO2 was produced. In tube 4 (60ºC), 3.3 ml of CO2 was produced. In tube 5 (100ºC), 0.2ml of CO2 was produced.

B: In tube 6 (galactose), 0.2ml of CO2 was produced. In tube 7 (sucrose), 4.0ml of CO2 was produced. In tube 8 (fructose), 4.7ml of CO2 was produced. In tube 9 (maltose), 2.5ml of CO2 was produced. In tube 10 (lactose), 0.45 CO2 was produced. In tube 11 (lactose+lactaid), 4.25ml of CO2 was produced.

Discussion:

In part A, the data and the graph successfully supported the hypothesis. From the data, the most optimal temperature to produce the most CO2 is 45°C. 0°C and 100°C were too low and too high for the reaction, so that there was little CO2 produced. The 60°C was near to the 45°C, but it was still suboptimal. Therefore, the volume of CO2 produced under 60°C was less than the one under 45°C. This lab proved that the incubation temperature could influence the work done by the enzyme (Malinoski 73). The higher or lower temperature could denature or block the function of the enzyme, and the sub-optimal temperature had lower efficiency of the enzyme. The data was reliable by following the instructions on the lab manual. There were some errors occurred during the lab influencing the final data. When the tube in the vial was inverted, the tube was not held tightly to touch the bottom of the vial; therefore, there was some extra CO2 produced. Also, when the vial was placed in the hot water bath, the tube might not stay tightly close to the bottom of the vial; the extra CO2 might also produce.

In part B, the data from the table 3 supported the hypothesis that the tube with galactose and lactose had no or less CO2 produced. Because the galactose was a different sugar that could not break down by enzyme, so there was no CO2 produced. In the same way, the lactose was formed by galactose and glucose, therefore, there was also no CO2 produced. The data was reliable by following the instructions in the manual. However, there was some error occurring during the lab. The CO2 produced in the tube with lactose was 0.45mL, but the CO2 produced in the tube with galactose is 0.2ml. There must be some error occurred. When the tube in the vial was inverted, the tube was not held tightly to touch the bottom of the vial; therefore, there was some extra CO2 produced. Also, when the vial was placed in the hot water bath, the tube might not stay tightly close to the bottom of the vial; the extra CO2 might also produce.

Figures:

Part1: Table 1 Percent transmittance (%T) at 600nm

Part 2-A: Temperature and Carbon Dioxide Production

Part 2-B: Sugar Sources and Carbon Dioxide Production

References:

1. Malinoski, Chris. Biology 1107: Principle of Biology---Laboratory Manual. Michihan, Hayden-McNeil, 2018 (Malinoski 73)

2. Elmer Stotz and A.Baird Hastings, The Components Of The Succinate-Fumarate-Enzyme System, January.29th, 1937