In the mitochondrial disease MNGIE a deficiency of thymidine phosphorylase causes dTTP to accumulate in mitochondria. Describe the mechanism by which this occurs. A secondary effect is depletion of mitochondrial dCTP pools. Describe a plausible mechanism for this effect.
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In the mitochondrial disease MNGIE a deficiency of thymidine phosphorylase causes dTTP to accumulate in mitochondria. Describe the mechanism by which this occurs. A secondary effect is depletion of mitochondrial dCTP pools. Describe a plausible mechanism for this effect.
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- Leigh syndrome is characterized by psychomotor regression: that is, the progressive loss of mental andmovement abilities. Patients also suffer from lacticacidosis, a condition in which mitochondrial respiration is deficient, so their tissues metabolize glucoseanaerobically, leading to the buildup of lactate. Somepatients with Leigh syndrome have a mutation in themitochondrial gene MT-CO3, which encodes a subunit of the electron transport complex cytochromec oxidase. Other patients diagnosed with Leigh syndrome have a loss-of-function mutation in the nucleargene SURF1, which encodes a factor needed for theassembly of this same enzyme complex.a. How can the same symptoms result from mutationsin a mitochondrial gene and from mutations in anuclear gene?The enzyme dihydrofolate reductase (DHFR) normally resides in the cytosol, and it can be imported into mitochondria by appending a mitochondrial signal sequence. However, when this modified DHFR is incubated with methotrexate, which is a substrate analog that binds tightly to the active site, the modified DHFR is no longer imported. Propose an explanation for this finding.In the presence of oxygen, the mitochondrion in yeast is used for aerobic respiration,however, under anaerobic conditions,the yeast mitochondria have been found to have other function. Identify and briefly discuss four of these functions
- Citrate synthase is a nuclear-encoded enzyme of the Citric Acid Cycle. The enzyme is functional in the mitochondrial matrix. Looking at the system required for mitochondrial targeting and import of citrate synthase, which of the following statements are correct? 1. Proper import and processing of citrate synthase is dependent upon other proteins found in the mitochondria. 2. Because of the signal peptide, the mature functional enzyme is actually longer than it would be if it was coded by the organelle genome. 3. Because the citrate synthase signal peptide doesn’t have a precise amino acid signature, mutations that slightly change the primary sequence have no effect on targeting. 4. To get citrate synthase into the mitochondrial matrix requires two signal sequences: one to get it across the outer membrane and a second to get it across the inner membrane. A. 1,2 and 3 B. 1 and 3 C. 2 and 4 D. 4 only E. All of 1,2,3 and 4 are correctComplex II contains one heme b moiety that is not in the direct path of electron transfer. It may serve instead to decrease the frequency with which electrons leak out of the system to produce reactive oxidative species (ROS). Discuss the correlation between a defective heme b in Complex II and the development of certain types of cancer. What are some of the mechanisms by which the oxidative stress caused by ROS is alleviated? What are some of the damaging effects of ROS? How might these damaging effects lead to cancer?Von Gierke’s disease is also known as glycogen storage disease type I. Patients with von Gierke’s disease lackglucose 6-phosphatase activity. Two prominent symptoms of this disorder are fasting hypoglycemia and lactic acidosis (elevated lactate levels in the blood), especially during strenuous exercise. Explain why these symptoms occur. What chemical reaction does this enzyme catalyze? Which pathways involve this enzyme? Lacking thisthe enzyme will cause impairment of which pathways?• Pls consider what pathways are affected by Von Gierke’s disease. Include in your explanation involving Cori’s cycle. can you please do not write by your hand? I mean computer if you can. thank you
- Von Gierke’s disease is also known as glycogen storage disease type I. Patients with von Gierke’s disease lackglucose 6-phosphatase activity. Two prominent symptoms of this disorder are fasting hypoglycemia and lactic acidosis (elevated lactate levels in the blood), especially during strenuous exercise. Explain why these symptoms occur. What chemical reaction does this enzyme catalyze? Which pathways involve this enzyme? Lacking thisenzyme will cause impairment of which pathways?• Pls consider what pathways are affected by Von Gierke’s disease. Include in your explanation involving the Cori’s cycle.Gluconeogenesis is a process that synthesize glucose from noncarbohydrateprecursors, which requires oxaloacetate as intermediates. The generation ofoxaloacetate only occurs in the mitochondria. For the species that has PEPCK inthe cytosol, briefly explain, with illustration, how oxaloacetate is transported out of the mitochondria to be used in gluconeogenesis.The c subunits of the Fo component of mitochondrial ATP synthase form a ion channel through the inner membrane. When any of the essential waste C subunit aspartate reacts with dicyclohexylcarbodiimide (DCCD) the subunit is unable to carry out proton transport. a. How will DCCD affect mitochondrial electron transport? b. What might you expect to happen when a decoupling agent is added (e.g. example dinitrophenol) to mitochondria treated with DCCD? c. How would ATP synthesis be affected in the above cases? Reasons the reply.
- A person with a hereditary deficiency realated to mitochondrial fatty acid oxidation shows accumulation of a long-chain acylcarnitine in the mi- tochondrial matrix. What factor could be responsible for this disorder? Provide a biochemical explanation for its mechanism of action.Calcium is an important regulator of the citric acid cycle. Calcium is transported across the mitochondrial inner membrane by a Ca²- 2+ uniporter that is driven by the negative potential inside the matrix. Part A Assuming a membrane potential across the inner membrane of 172 mV (inside negative), calculate the ratio of the [Ca2+] in the matrix to that in the cytoplasm ([Ca2+]m/[Ca²+]c) that would exist at equilibrium (i.e., AG = 0). Express your answer using two significant figures. [Ca2+]m [Ca2+] = ΤΟ ΑΣΦ Submit Request Answer Part B ? Cytoplasmic [Ca2+] is on the order of 10-7 M in a healthy cell. Based on your answer in Part A, calculate the [Ca2+] that would exist in the matrix at equilibrium. Express your answer to two significant figures and include the appropriate units. ☐ μÅ ? Value UnitsThe enzyme dihydrofolate reductase (DHFR) normally resides in the cytosol, andDHFR can be imported into mitochondria by appending a mitochondrial signalsequence. However, when this modified DHFR is incubated with methotrexate, whichis a substrate analog that binds tightly to the active site, the modified DHFR is nolonger imported.a) Propose an explanation for why methotrexate prevents import of DHFR intomitochondria.b) Suppose that DHFR were modified instead by appending a nuclear localizationsignal. Would you expect methotrexate to prevent transport of this modified DHFRinto the nucleus? Why or why not?
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