Cellular Respiration

Topics: Carbon dioxide, Yeast, Adenosine triphosphate, Metabolism, Ethanol, Alcohol / Pages: 7 (1686 words) / Published: May 3rd, 2013
Lab 8 Cellular Respiration and Fermentation

Objectives: 1. Observe the effects of cellular respiration on temperature in a closed system. 2. Investigate carbon dioxide production in both germinating pea seeds and crickets. 3. Perform an investigative study of the rate of cellular respiration in both pea seeds and crickets at various temperatures. 4. Compare the alcoholic fermentation of glucose, sucrose, and starch by yeast.

Introduction

All organisms must have a continual supply of external energy in order to maintain bodily functions and to combat entropy. Ultimately this source of energy is the sun. As you learned in the previous lab, plants can convert the sun’s energy into usable forms of chemical energy (E.g., glucose). In order for the energy to be made useful the chemical bonds that hold the atoms of these molecules together must be broken. The released energy is captured by high-energy phosphate bonds and combined with adenosine diphosphate (ADP) to form adenosine triphosphate (ATP), which is the energy currency of the body.

There are two processes that release this energy from the photosynthetic materials to form the energy molecule ATP. Those processes are cellular respiration and fermentation. Cellular respiration is an aerobic (requires oxygen) process, while fermentation is an anaerobic (occurs without oxygen) process. These enzyme-controlled reactions that occur during these processes are both oxidative (loss of electrons) and reductive (gain of electrons). Because the reactions are enzyme controlled they require less activation energy and therefore occur at nonlethal temperatures, continually releasing small amounts of energy that can be used to from ATP.

When compared to fermentation, the formation of ATP via cellular respiration is a relatively efficient process, as there are 36-38 ATP molecules formed per glucose molecule. Fermentation on the other hand only generates a net of 2 ATP molecules. This may

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