Question

1. Why do fats provide more energy per molecule than glucose? Explain your answer in terms of the electrons extracted during the process of cellular respiration. 2. A rare, frameshift genetic mutation can alter the structure of the Pyruvate Dehydrogenase Complex such that it no longer functions within the cell. Describe what parts of the process of cellular respiration would be impacted due to this non- functional enzyme. 3. The citric acid cycle functions to completely oxidize glucose in the presence of oxygen, allowing for a large amount of ATP to be produced within the cell through oxidative phosphorylation. Free oxygen did not always exist within the atmosphere of Earth, meaning that early life forms relied solely on glycolysis and fermentation to extract energy from macromolecules. What role did the increase in atmospheric oxygen play in the evolution of life on Earth? Frame your answer in terms of the energy derived from cellular respiration in the presence and absence of oxygen. 4. A rare, fake disease that I just made up called Leaky Inner Membrane Syndrome can lead to the formation of Hydrogen Ion Channel proteins within the inner membrane of the mitochondria. These channel proteins allow for the diffusion of hydrogen ions across the inner mitochondrial membrane according to their concentration gradient. Considering your knowledge of the electron transport chain and its role in oxidative phosphorylation, how would this disease affect the metabolism of an affected individual? Be specific! 5. An evil mad scientist is working on creating a modified human that is capable of surviving the vacuum of space! One of the many challenges this scientist faces is trying to find a way to combat the extremely cold temperatures of space. The membranes of the test subjects keep losing their fluidity, preventing them from exchanging materials with their outside environment. What can the mad scientist do to retain the fluidity of the cellular membranes? How can the composition of lipids (saturated vs unsaturated fatty acids, cholesterol content) be modified to allow the individuals to survive the cold temperatures? Why should these changes be made? 6. Why do most molecules require the assistance of proteins to cross the cellular membrane? What factors limit diffusion of molecules across the cellular membrane?

Answer 1

1. One glucose molecule theoretically produce 38 moles of ATP when it is completely oxidsed by undergoing two cycles of TCA.

When a fatty acid for example palmitic acid (16C) undergoes beta oxidation to produce energy, it will provide 8 molecules of acetly CoA. Each acetyl CoA molecule will undergo TCA cycle to produce ATP. One TCA cycle gives 12 molecules of ATP. Then, 8 cycles of ATP per molecule of fatty acid wolud give more ATP than a glucose molecule.

2. Oxidatve decarboxylation ( formation of acetyl CoA) is done by the enzyme pyruvate dehydrogenase compex. This is a preparative phase of TCA cycle. So if the enzyme is non functional then both preparative step and TCA cycle will be affected.

3. ATP is the only source of energy for the survival of any organism. So, anaerobic bacteria produces ATP through glycolysis by anaerobic respiration/ fermentation. But, fermentation produce only 2 molecules of ATP. This will be sifficient for a unicellular organism to survive. But, what about multi cellular organisms who needs more ATP for their metabolic activity. Thats why presence of oxygen made an another way to produce more ATP. Aerobic glycolysis gives 38 moles of ATP. Therefore, it is clear that, oxygen played a very important role in the evolution of multicellular organisms.

4. Electron Tansport Chain uses reducing equivalents NADH2 and FADH2 to push the protons [H+] out of the matrix into intermembrane space against concentration gradient. This forms a higher proton gradient across the mitochodrial inner membrane. This is gradient is the reason for the ATP production by ATP synthase. If there is a leaky membrane then, the production of ATP by oxidatve phosphorylation will be affected.