Biology 225- Cellular Energy Lab

Biology 225- Cellular Energy Lab - Cellular Energy...

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Cellular Energy Module—Week 1 (Adapted from Laboratory Investigations for Biology 2 nd ed., Jean Dickey, 2003) Learning Objectives: By the end of this laboratory module, you should be able to: 1) Describe fermentation, aerobic respiration, and photosynthesis including naming the substrates and products. 2) Explain how fermentation, aerobic respiration, and photosynthesis can be measured. 3) List factors that can affect the rates of fermentation, aerobic respiration, and photosynthesis. 4) Propose a hypothesis about how a particular factor impacts fermentation, aerobic respiration, or photosynthesis. 5) Design and perform an experiment to test your hypothesis. 6) Interpret and analyze the results of your experiment. 7) Present your experiment and findings to the class. Module timeline: Day 1: Perform aerobic respiration and fermentation experiments Day 2: Perform photosynthesis experiment; develop hypothesis; design experiment Day 3: Conduct experiment; analyze data; present to class DAY 1: AEROBIC RESPIRATION & FERMENTATION Background: The energy contained within a molecule of glucose cannot be used directly by the cell. The energy must be repackaged into the high energy bonds of adenosine triphosphate, or ATP. The process of cellular respiration transfers the energy stored in glucose bonds to bonds in ATP so that it may be used more easily by the cell. Each glucose molecule can generate as many as 38 molecules of ATP via cellular respiration. In today’s lab, we will examine two methods by which cells make ATP via breaking down the chemical bonds in glucose. Aerobic Respiration Most organisms, including humans, produce most of their ATP using aerobic respiration. Aerobic respiration begins with glycolysis. The end product of glycolysis, pyruvate, enters the Kreb’s Cycle where reducing power is generated in the form of NADH and FADH 2 . These electron carriers donate electrons to the electron transport chain. As electrons pass along the chain, a proton gradient is established across the mitochondrial inner membrane. As protons flow back across the membrane through ATP Synthase, ATP is synthesized. In aerobic respiration the final electron acceptor is O 2 , hence the name aerobic respiration.
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Fermentation Fermentation is a metabolic pathway used primarily by yeasts and some bacteria. Glucose is broken down into pyruvate as in aerobic respiration. In contrast to aerobic respiration, fermentation does not involve O 2 and the pyruvate molecules do not enter the Kreb’s Cycle. The pyruvate molecules are converted via particular enzymes into products such as lactic acid, ethanol, and CO 2 . The electrons carried by NADH are not donated to the electron transport chain; rather these are accepted by organic molecules. The breakdown of glucose and conversion into fermentative products only yields 2 ATP (note that these are the 2 net ATP produced during glycolysis).
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