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
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
Related questions
Question
Transcribed Image Text: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
0.5
A
Succinate a-glycerol-
phosphate
0.4
0.3
0.2
01
4.
B
Malate Glutamate d-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?
Expert Solution
Dehydrogenases
Dehydrogenases are a group of enzymes with the ability to extract high energy electrons and also equivalent number of protons from substrates and then transfer these to some coenzymes . The substrate gets oxidized and the coenzyme gets reduced . The reduced coenzymes then transfer these high energy electrons to the electron transport chain which leads to ATP synthesis.
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