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K101 LAB EXERCISE 6 CELLULAR RESPIRATION AND FERMENTATION All living organisms have a constant need for cellular energy, and have metabolic pathways to collect, store, release and use ATP energy. The major metabolic pathway by which a cell breaks down macromolecules and releases the energy to the cell is called cellular respiration . . Energy contained within the C-H bonds of carbohydrates or other macromolecules is transferred to ATP during respiration. This stored energy can be transferred later to power a wide variety of cellular reactions by phosphorylation . Cellular respiration may be anaerobic or aerobic , depending on the availability of O 2 . During aerobic respiration , high-energy macromolecules like glucose are broken down in a series of metabolic steps. (1) Glycolysis breaks glucose down into two molecules of pyruvate. Pyruvate enters the mitochondria, where enzymes of the (2) Kreb’s cycle strip all the hydrogen atoms from the pyruvate, releasing CO 2 . The hydrogen ions (H+) and their associated electrons pass through a series of mitochondrial membrane carriers called (3) the Electron Transport Chain , where they are ultimately captured by oxygen , forming water (H 2 O) and ATP via a process called (4) oxidative phosphorylation . For aerobic respiration of glucose, the overall equation is C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ~36-38 ATP Given the equation above, you may be able to spot at least four ways cellular respiration could be measured: 1. Consumption of glucose (or another sugar) 2. Consumption of O 2 3. Production of CO 2 . 4. Release of ATP energy during cellular respiration. In this K101 lab, we will measure the two most straightforward of the options above: the relative volume of O 2 consumed by germinating seeds and by the bacteria present in milk, and the amount of CO 2 produced during both aerobic respiration and alcoholic fermentation in yeast. Fermentation is an anaerobic process for ATP production that produces ethanol or other waste products from glucose, releasing only 2 ATP per glucose, plus in some cases a large quantity of CO 2 gas. Fermentation is an important means of energy production for manya living organisms, particularly many bacterial and yeast species. Objectives: After this lab, you should be able to 1. Define metabolism, phosphorylation, glycolysis, 2. State the overall equation reaction for aerobic respiration 3. Describe two ways to measure O 2 consumption and two ways to measure CO 2 production in living cells. What is the purpose of Phenol Red, Methylene Blue, and KOH pellets in the experiments we perform today? 4. New Techniques: Set-up and use, and analysis of data from respirometers and fermentation tubes 1
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A. Consumption of O 2 via the Methylene Blue test [ 2 hour incubation, readings every 30 min ] Milk is a sterile fluid produced by lactating female mammals that contains a nutritious mix of proteins, sugars, and other macromolecules for a developing baby. As such, it is also an ideal substance for supporting bacterial growth should a sample be removed from an animal (for
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