Question

Sucrose can be used as carbon source by a number of microorganisms. Calculate the number of ATP generated by assuming that microorganisms capable of utilizing glycolysis, citric acid cycle, and oxidative phosphorylation. Also, assume glycerol-phosphate shuttle is used during transfer of NADH from cytoplasm to mitochondria.

Answer 1

Same number of ATP will be produced when sucrose or glucose is fed into the glycolysis because only glucose can enter the glycolysis, hence sucrose has to be converted to glucose before entering into glycolysis. You can see the journey of a sucrose molecule through metabolism and finally how much ATP is produced is also shown-

1- entry of sucrose molecule into glycolysis-

Sucrose UDP Sucrose SUS tsFru Invertase UDPglc PPİ UGPase Gluc UT ATP HK G1P PGM PGI Starch synthesis G6P F6P PGI Starch HP Pool Glycolysis Pyruvate Ac-CoA Fatty acids TCA cycleAmino acids Oil Proteins

2- Total number of ATP produced-

cytoplasm o glucose 2 ATP ATP glycolysis energy input to start reactions (2 ATP net) 2 NADH 2 pyruvate mitochondrion e +H 2 NADH 6 NADH e +H 2 FADH2 e+ H 4 CO2 Krebsj Cycle 2 ATP ELECTRON TRANSPORT PHOSPHORYLATION 32 ATP water 0 он. e + oxygen TYPICAL ENERGY YIELD: 36 ATP

3. Glycerol phosphate shuttle-