Question

Assume a cell has just completed glycolysis and the resulting pyruvate has a c-14 radio label on carbon -1. Highlight the carbon on the attached pages as it passes through the PDH complex and the TCA cycle until it is lost as CO2. If only a portion of the carbons are lost stop highlighting when the CO2 first starts to come off. ONLY ONE TIME THRU THE CYCLE ON EACH PAGE

2. Repeat question 1 but now assume the radio label is on carbon -2 of pyruvate.

3. Repeat question 1 but now assume the radiolabel is on carbon-3 of pyruvate

B-exidation of fatty acids) dehydrogenase CoASH CO2 Acetyl-CoA NADNADH, H+ CoASH -coo Oxaloacetate HO HO--coo. не-соо- Citrate synthaseCitrate NADH, H+ -coo dehydrogenase #1 Aconitase Malate #8 #2 -соо- H-C-COO- но-с-соо. Fumarase #7 Krebs cycie Tricarboxylic acid (TCA) cycle Citric acid cycle нс-соо. Isocitrate #3 NAD+ socitrate is。 dehydrogenase NADH, H+ Succinate co #4 #5 FAD H2-coo Sueciny CoA ketoglutarate -coosynthetase dehydrogenase NAD+ NADH, H* C-C00. GTP H2C-co0. GDP. P a-ketoglutarate Succinate CoASH COASH Succinyl-CoA

Answer 1

1.As per the given details it is clear that C₁ of pyruvate is radiolabelled with C_14. Through the series of sequential steps in above cycle we can estimate that a carbon from pyruvate carbon skeleton chain starts coming off during the conversion of succinate to fumerate because the CH₂ loses one proton in this step.

ol CoASH H1 C-c00- Malst но-с-соо- HH C-Coo- (C.trate) CYUL Hc-coo C-co0 SuctinaG HC-Coo HLC-coo- Lioctrat CHL (x-lketoglutwat)

2.When C₁₄ is labelled at 2nd carbon of pyruvate it is cycled continously as shown below .This shows that second carbon of pyruvate is participated in formation all the intermediate products and is continously cycled in kerbs cycle.

HC-C-C-O Molate Co ASH 해 100.// kla inom (0AA) H0 C-C00-4 HC-Coo- HC-C60- HO-C-Co0- c-coo- umerase TCA CVCLE H20 (C trat) WADt WADH,H HC-CoO Sucunae HC-COO FAD nase -Oo- lo c Hi HL C-Coo- -ketoglu tava CHi l Co-A) uttih

3.When 3rd carbon of pyruvate is radiolabelled with C₁₄  then during formation of acetyl Co-A the radiolabelled C₁₄ is released in the form of CO₂. This means that the radiolebelled C₁₄ carbon do not enters Krebs cycle.

HC-C-C-O 누 HLC-C-5-CoA Malate o=c-coo- nate HC-coo CoASH itvate Synthetase HC-C00- (Malet) но-с-соо- t umerase TCA CYCLE H10 (C trat) WADt HC-Coo HC-coo FAD HiC-Coo - crognase Hi C-(00- CHL HL CHi