PSET2S - Solutions for 2010 7.012 Problem Set 2 Question 1...

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1 Solutions for 2010 7.012 Problem Set 2 Question 1 E. coli bacteria cells use glucose as an energy source both under aerobic (in the presence of oxygen) and anaerobic (in the absence of oxygen) growth conditions. In the absence of oxygen, these bacteria consume large amounts of glucose. However, their rate of glucose consumption decreases if they are grown in the presence of oxygen. a) Why do the bacterial cells require less glucose for the same growth rate once oxygen is added? In the presence of oxygen, the cells can use glucose in aerobic respiration as opposed to fermentation. The net energy yield per glucose molecule in respiration is much higher than in fermentation, so less glucose is needed for the same amount of growth under aerobic conditions. An outline of photosynthesis is shown below. b) In a manner analogous to that shown above, i. Complete the diagram for glycolysis: ii. Complete the diagram for the overall process of respiration (respiration = glycolysis + citric acid cycle + oxidative phosphorylation): iii. Glycolysis occurs in the absence of oxygen. What happens to the carbon containing molecule produced in glycolysis when the cell is undergoing fermentation? Is any additional ATP produced? The electrons from NADH are given to pyruvate, which is converted into ethanol or lactic acid. This regenerates the NAD + needed to continue glycolysis, but does NOT generate any additional ATP. CO 2 ATP ADP Glucose + NADPH O 2 NADP+ H 2 O + Note: For part b) include the names of the following molecules wh e r e app l i cab l e : g luco s e , py ruva t e, CO 2 , NAD + , NADH, O 2 and H 2 O, ATP and ADP. You do not need to include any other carbon intermediate or the names of the enzymes that catalyze specific reactions. glucose pyruvate ADP ATP NAD+ NADH Glucose + O 2 ATP ADP NADH NAD+ CO 2 + H 2 O
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2 Question 1, continued c) Oxidative phosphorylation is a series of oxidation-reduction reactions carried out by the proteins of the electron transport chain (ETC). i. What molecule donates electrons to the first protein in the ETC? NADH ii. Name the final electron acceptor used during oxidative phosphorylation in aerobic conditions.
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This note was uploaded on 03/12/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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PSET2S - Solutions for 2010 7.012 Problem Set 2 Question 1...

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