In early studies of cultured cells, a respi- ration-deficient mutant of Chinese hamster fibroblasts was found. The respiration rate of the mutant cell line was only -8% of the wild type cell line. It was determined that that all enzymes of the Krebs cycle or Tri- carboxylic Acid Cycle were present in the mutant. Also, absorption spectra of the cy- tochrome content of mitochondria showed no deficit in cytochrome content. Various assays were carried out and results are il- lustrated below. moles 0₂ consumed/hr/mg protein 2.0 15 1.0 0.5 Succinate a-glycerol- phosphate 0.4 03 02 OI B Malate Glutamate ad-Keto- Isocitrate glutarate (a) Rates of reduction of O2 catalyzed by wild type and mutant mitochondria and supported by oxidation of substrates are compared by the histogram graph on the previous page. Open bars rep- resent Wild Type mitochondria; cross-hatched bars represent the mutant mitochondria. Oxidation of each of the substrates in the two graphs requires a coenzyme. On what basis are the substrates separated into graphs A and B? (a-glycerol-phosphate in the figure legend is an old term for glycer- ol-3-phosphate.) (b) Compare the pathways for oxidation of succinate and glycerol-3-phosphate. Use struc- tural formulas except for coenzymes/cofactors and enzymes, and name enzymes, substrates, and products. How do they differ with respect to source of the substrate and what common features do they possess? (c) Compare the number of moles of ATP that are synthesized per mole of glucose under aer- obic conditions in the cytosol and in the mitochondria of wild type and mutant Chinese hamster cells. (Assume 2.5 equivalents ATP produced/cytosolic NADH and 1.5 ATPs/FADH2.) Indicate the key steps from which the number of equivalents of ATP can be calculated. (d) How did the mutant Chinese hamster cells synthesize sufficient ATP to survive because it was stated that the respiration deficient mutant Chinese hamster cells were associated with a rate of O2 consumption that was only 8% of that of the wild type cells?

In early studies of cultured cells, a respi- ration-deficient mutant of Chinese hamster fibroblasts was found. The respiration rate of the mutant cell line was only -8% of the wild type cell line. It was determined that that all enzymes of the Krebs cycle or Tri- carboxylic Acid Cycle were present in the mutant. Also, absorption spectra of the cy- tochrome content of mitochondria showed no deficit in cytochrome content. Various assays were carried out and results are il- lustrated below. moles 0₂ consumed/hr/mg protein 2.0 15 1.0 0.5 Succinate a-glycerol- phosphate 0.4 03 02 OI B Malate Glutamate ad-Keto- Isocitrate glutarate (a) Rates of reduction of O2 catalyzed by wild type and mutant mitochondria and supported by oxidation of substrates are compared by the histogram graph on the previous page. Open bars rep- resent Wild Type mitochondria; cross-hatched bars represent the mutant mitochondria. Oxidation of each of the substrates in the two graphs requires a coenzyme. On what basis are the substrates separated into graphs A and B? (a-glycerol-phosphate in the figure legend is an old term for glycer- ol-3-phosphate.) (b) Compare the pathways for oxidation of succinate and glycerol-3-phosphate. Use struc- tural formulas except for coenzymes/cofactors and enzymes, and name enzymes, substrates, and products. How do they differ with respect to source of the substrate and what common features do they possess? (c) Compare the number of moles of ATP that are synthesized per mole of glucose under aer- obic conditions in the cytosol and in the mitochondria of wild type and mutant Chinese hamster cells. (Assume 2.5 equivalents ATP produced/cytosolic NADH and 1.5 ATPs/FADH2.) Indicate the key steps from which the number of equivalents of ATP can be calculated. (d) How did the mutant Chinese hamster cells synthesize sufficient ATP to survive because it was stated that the respiration deficient mutant Chinese hamster cells were associated with a rate of O2 consumption that was only 8% of that of the wild type cells?

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter21: Photosynthesis

Section: Chapter Questions

Problem 5P: The Relative Efficiency of ATP Synthesis in Noncyclic versus Cyclic Photophosphorylation If...

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