201. Biology Homework on Chapter 9 1. Describe what happens to pyruvate if sufficient oxygen is present. If enough oxygen is present, pyruvate continues to be catabolized and goes to the Krebs cycle, where it will produce NADH and FADH2 in order to produce ATP in the electron transport chain. 2. in step 6 of the citric acid cycle, succinate is converted to fumarate. The reaction is coupled to the conversion of FAD to FADH2. Would succinate or fumarate have more carbon-hydrogen bonds? Is succinate being oxidized or reduced? Why is FAD being used here instead of NAD? Succinate has more energy than fumarate, and this is because succinate has more carbon-hydrogen bonds. Succinate is being oxidized into fumarate. There is not enough energy to reduce an NAD, so an FAD is made instead. 3. Aliens land at UNM. You find that in almost all ways, their metabolism is identical to that of humans. One important difference is that they do not use NAD/NADH. At every step in the oxidation of biological molecules where humans use NAD/NADH aliens use FAD/FADH-2. At steps where humans use FAD/FADH-2, the aliens do as well. a. Who makes more ATP/mole of glucose, aliens or humans? Explain b. Who makes more ATP by substrate level phosphorylation? Humans will make more ATP per glucose because we make 3 ATP per each NADH, while aliens would only make 2 ATP per FADH2. Humans will make more ATP by substrate level phosphorylation because we make more ATP per glucose than they do.
4. Consider a cell that can normally grow either with or without oxygen . You also have a mutated strain of this same cell type. In the mutated strain, citrate synthetase is present in a mutated form. The enzyme still converts reactant normally produce to but no allosteric molecules can bind the allosteric site. In the absence of oxygen, will the mutated cell make less more or the same ATP than the normal cell? How about in the presence of oxygen? Because of feedback inhibition, the cell will continue to make ATP, regardless of if the oxygen is present or not. 5. How is ATP made in electron transport? Provide full details. This occurs in the mitochondria, and NADH is oxidized to NAD on Complex I. Complex I now has energy to pump some H ions against concentration gradient from mitochondrial matrix into intermembrane complex. C I will reduce Coenzyme Q, then
CoQ reduces C III, which will pump H ions by accepting an electron and then reduce Cytrochrome C. Cytochrome C reduces C IV and C IV will pump H ions into intermembrane complex. The next step is known as chemiosmosis and the H ions will flow through ATP synthase, which will allow the rotor to turn and convert the chemical energy in the H ions into mechanical energy. Then the synthase knob, which had a conformational change because of the turning of rotor, will synthesize the ATP in the matrix. 6. Why, in eukaryotic cells, does an NADH from glycolysis result in only 2 ATP but in prokaryotes it results in 3 ATP? In eukaryotic cells, energy is spent to bring in NADH into the mitochondria, and on prokaryotes, glycolysis occurs in the cytoplasm instead. 7. If in an experiment, protons could somehow rapidly be removed from the inner membrane space, how would this affect ATP synthesis by electron transport? If the protons were removed from the intermembrane space, ATP production will cease because it is these protons that activate ATP synthase in order for it to start producing ATP.