1. In the conversion of pyruvate (PYR) to phosphoenolpyruvate (PEP) in gl the ad
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Question
1. In the conversion of pyruvate (PYR) to phosphoenolpyruvate (PEP) in gl the addition of CO, is followed by a decarboxylation. Why would nature add the CO, only to remove it in the next step? Is the carbon added the same as the one removed? 2. HC-glucose (with ONLY carbon 5 radioactively labeled s.14C glucose) is given to metabolically active 6 phosphate of the cells liver cells in cell culture. The cells are isolated after a short time and the gl analyzed. The glucose-6-phosphate contains the 4C label in the carbon S and carbon 2 positions. Explain these observations 3. On the basis of simply counting carbons, a student proposes that 2 oxaloacetate molecules and one palmitate molecule, following the normal metabolic pathways, can be made into four molecules of glucose via gluconeogenesis. Identify and explain the flaw in this conclusion. 4. Explain metabolically how camels have evolved to live in the desert where little to no water is present. 8. Inhibitors of fatty acid degradation are used to relieve angina (heart pain) resulting from insufficient oxygen. Wby does this make sense? Under starvation conditions the body does not have incoming food and must use available stores for energy production. What are the three available stores of energy? Which will be depleted first? 2. to get down to the Calculate the net ATP yield for the following tripeptide assuming no energy is required Gly-Met-Leu 7:44/8:04Explanation / Answer
1. In gluconeogenesis, the reaction takes place inside the mitochondria. Pyruvate is carboxylated (CO2 added) to Oxaloacetate. The Oxaloacetate is subsequently reduced to Malate using NADH. The conversion to Malate is important since it can easily move out of the mitochondria. Once in the cytosol, Malate is oxidised to Oxaloacetate using NAD+. Oxaloacetate is decarboxylated and phosphorylated to form phosphoenolpyruvate.
The purpose of adding carbon dioxide was to convert the substrate to Malate so that it can move out of the mitochondria and continue gluconeogenesis in the cytosol as it is reconverted to oxaloacetate here.
4. The survival of Camels in deserts is owed to the excellent ability of their kidneys to recycle water and keep them hydrated at all times. In addition camels do not sweat until their body temperature touches 41 degrees celsius. Camels rarely urinate and when they do they pass little volume of very concentrated urine, also their excreta is very dry and pelleted to prevent water loss. They also reduce respiratory water losses by reducing the frequency of their breaths per minute.
8. Because a lot of oxygen is consumed during fatty acid oxidation. Most long chain fatty acids are not handled by mitochondria in the cells but by proxisomes which uses the same enzymes to produce acetyl COA from fats. However unlike the mitochondria, the high potential electrons here do not produce ATP but are neutralised using oxygen. Oxygen is reduced to hydrogen peroxide with the generation of a lot of heat. The oxygen is subsequently recycled and used with the help of the enzyme Catalase.
2. Under starvation conditions the body uses the following stores of energy production in the given sequence -
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