Question

Biochemistry II: Calculating ATP from beta-oxidation

In calculating the number of ATP molecules generated by the beta-oxidation of a single fatty acid molecule with an even number of carbons,

a) Identify how the P/O ratios can be used (what are their significance),

and b) help me to construct a formula given the P/O value of 3 for NADH and 2 for FADH₂.

Answer 1

Calculating ATP from beta-oxidation:

answer:

- oxidation: It is defined as the metabolic process which involves fatty acids are broken down into produce energy

i. Palmitoyl-coA + 7CoA + 7 FAD + 7 NAD⁺ + 7 H₂0 -------------> 8 acetyl coA + 7 FADH₂ + 7 NADH + 7H⁺

ii. 8 Acetyl coA + 16 02 + 96 Pi + 96 ADP     -------------------> 8 coA + 96 ATP + 104 H20 + 16 C02

iii. Overall reaction:

Palmitoyl-coA + 23 0₂ + 131 Pi + 131 ADP -----------------> coA + 131 ATP + 16 C0₂ + 146 H₂0

yield of ATP during one molecule palmitoyl-coA to C02 to H20

S.no.	Enzyme catalyzing oxidation steps	Number of NADH2 or FADH2 formed	number of ATP formed
1.	Acy-coA dehydrogenase	7 FADH2	14
2.	Hydroxyacyl coA dehyrogenase	7 NADH	21
3.	Isocitrate dehydrogenase	8 NADH	24
4.	ketoglutarate dehydrogenase	8 NADH	24
5.	Succinyl-CoA synthetase		8
6.	Succinate dehydrogenase	8 FADH2	16
7.	Malate dehydrogenase	8 NADH	24
	Total =		131

                                                       Total = 131 ATP

for activation of palmitate to palmitoyl-coA = 2 ATP consumed

                                                          ------------------------

                                                          129 ATP

                                                          -----------------------

a) Identify how the P/O ratios can be used

b) construct formula given P/O value 3 for NADH and 2 FADH2

answer:

P/O ratio or phosphate / oxygen ratio refers to the amount of ATP produced from transfer of electron through ETC

Each FADH2 yields 1.5 ATPs and each NADH yields 2.5 ATPs

Beta oxidation (7 turns)

1 NADH per turn X 7 turns X 2.5 (P/O ratio)   = 17.5 ATP

1 FADH2 per turn X 8 turns X 1.5 (P/O ratio)   = 10.5 ATP

For TCA cycle (8 turns):

3 NADH per turn X 8 turn X 2.5 = 60 ATP

1 FADH2 per turn X 8 turn X 1.5 = 12 ATP

1 GTP /ATP per turn X 8 turn =     8 ATP

                                               -------------------

                                  Total   = 108 ATP    - 2 ATP ( for activation of fatty acid) = 106 ATP

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