Grossmont College Chemistry Problem Set Worksheet

The standard state Gibb’s free energy (ΔG°’) for synthesis of a particular acyl-CoA from its fatty acid and free Coenzyme A (CoASH) is +48.0 kJ/mol. Using this value and the information contained in Table 14-3 in your textbook, calculate the ΔG°’ value for each of the following reactions:

fatty acid + CoASH + ATP ⇌ acyl-CoA + ADP + Pi

fatty acid + CoASH + ATP ⇌ acyl-CoA + AMP + 2 Pi

Now write the equation and calculate the ΔG°’ value for the reaction as it would occur if catalyzed by the enzymes acyl-CoA synthetase and inorganic pyrophosphatase. What drives this reaction to occur spontaneously in the cytoplasm of cells?

• Camels can wander around in the desert for long periods of time without drinking water. One reason for this is their hump that is full of fatty tissue. Imagine a camel that contains 30 pounds of triacylglycerols in its hump. How much water could be obtained by complete beta-oxidation of the fatty acids contained in this mass of triacylglycerol. Assume that all the fatty acids in your camel are the saturated 16-carbon palmitate.

• Write out the sequence of reactions for the conversion of myristoyl-CoA to lauroyl-CoA and acetyl-CoA. Include the names of the enzymes and any necessary cofactors.

• If malonyl-CoA is synthesized from acetyl-CoA and 14CO2, where will the 14C end appear in palmitic acid?

The standard state Gibb’s free energy (ΔG°’) for synthesis of a particular acyl-CoA from its fatty acid
and free Coenzyme A (CoASH) is +48.0 kJ/mol. Using this value and the information contained in Table
14-3 in your textbook, calculate the ΔG°’ value for each of the following reactions:
1A) fatty acid + CoASH + ATP ⇌ acyl-CoA + ADP + Pi
1B) fatty acid + CoASH + ATP ⇌ acyl-CoA + AMP + 2 Pi
fatty acid + CoASH ⇌ acyl-CoA = ΔG°’ +48.0 kJ/mol
ΔG= ΔGproducts – ΔG reactants
1A) 48 KJ/mol= ΔG (acyl-CoA)- [ΔG fatty acid + ΔG CoASH}
ΔG= ΔG(acyl-CoA) + ΔG (ADP) + ΔG (Pi) – [ΔG(fatty acid) + ΔG (CoAsh) + ΔG (ATP)]
From table we get = 48 KJ/mol + 30.5 KJ/mol = 17.5 KJ/Mol
1B) ΔG= ΔG(acyl-CoA) + ΔG (AMP) + ΔG (P-Pi) – [ΔG(fatty acid) + ΔG (CoAsh) + ΔG (ATP)]
= 48 KJ/mol + ΔG (AMP) + ΔG (PPi) – [ΔG (ATP)]
= 48 KJ/MOL-45.6 KJ/Mol = 2.4 KJ/mol
Now write the equation and calculate the ΔG°’ value for the reaction as it would occur if catalyzed by
the enzymes acyl-CoA synthetase and inorganic pyrophosphatase. What drives this reaction to occur
spontaneously in the cytoplasm of cells?
So when Delta G is < 0 this process is spontaneous. They want to find the lowest energy state or the path of least resistance. Fatty acide + CoASH + ATP → Acyl-CoA + AMP + PPi = ΔG= 2.4 KJ/Mol acyl-CoA synthetase PPi → 2 Pi ΔG= -19.2 KJ/Mol from table inorganic pyrophosphatase Thus, overall reaction is = 2.4 KJ/Mol -19.2 KJ/mol = -16.8 KJ/mol. Since ΔG= is negative the reaction is spontaneous, irreversible, and has low barriers. If malonyl-CoA is synthesized from acetyl-CoA and 14CO2, where will the 14C end appear in palmitic acid? The 14 c will be in palmitic acid after 6 repeats of the cycle as Malonyl thio coenzyme ACP yristoy)-CoA) (M - 4A.R-CH CH2 -S-doA Acy|-CoA _I dehydrogenase. R-CH =C -C-S-CoA enoy|coA hydratee gH R-CHz: B -Cth NAD+ B/L-B: -hupatrokey! Col #GNADAHH dehydrogenase. R-CH -S-CoA Z C acy|-coa A Acy!- -S-Cot Beta Ketoaly). Cof -C-S-COlA (Lauroy)-CoA) (Acetyl-CoA.)