Question

From these 3 molecules: maltose, linoleic acid and histidine, completely solve:

2. What is the energy efficiency of the metabolism of these three molecules (total number of ATP molecules generated)?

3. What is the balance of coenzymes of great reducing power NADH and FADH2 in this metabolic integration of the 3 molecules?

4. Identify the regulatory points that occur in the metabolism of the three molecules.

5. Identify the cellular compartments where each of the phases of the metabolism of the three molecules take place.

Answer 1

Linoleic acid:

2) You get 122 ATP (minus 2 from the activation of fatty acid gives a total of 120 ATP) from: 3 b-oxidation cycles > isomerization > 1 b-oxidation cycle > reduction prior isomerization > 4 b-oxidation cycles.

3) 8 FADH2 and 8 NADH (when these go to Krebs Cycle they convert to 32 ATP) I'm omitting all the NADH/FADH2 related to Acetyl-CoA oxidation in Krebs Cycle.

4 and 5) The key steps in regulation of oxidation of fatty acids is in the transport of the fatty acid (in the form of Acyl-CoA) via the carnitine transporter located in the endoplasmic reticle and in the mitochondria.

Maltose:

2) You get 64-68 raw ATP (minus 2 from activation of each monosaccharide, a total of 60-64 ATP from a maltose molecule) it depends whether the electrons in cytosolic NADHs (these are 4) are translocated to mitochondria through malate-aspartate shuttle or glycerol-P shuttle.

3) 4 cytosolic NADH (that are converted to 4 NADH or 4 FADH2) and 4 NADH (when pyruvate is converted to Acetyl-CoA). I'm omitting all the NADH/FADH2 related to Acetyl-CoA oxidation in Krebs Cycle.

4 and 5) It occurs in the cytosol and is regulated by cytosolic AMPc concentrations and the activity of maltose transportator.

Histidine:

2) Histidine enters the krebs cycle via its conversion to a-ketoglutarate (involving 5 different enzymes), the a-ketoglutarate is mostly not oxidized because it's used by the cell as a reservoir of NH4+ acceptors (originated from the deamination of other aminoacidic) or is used to synthesize glucogen.

3) But, when is oxidized it produces 3 NADH + 1 FADH2 per a-ketoglurate entering krebs cycle.

4 and 5) The regulation occurs mostly at the activity of the deamination enzymes, this occur in peroxisomes.