Question

1.Determine the number of moles of ATP that can be synthesized from one mole of CH3(CH2)22COOH. (Show all your work.)

2.Why does the oxidation of unsaturated fatty acids such as oleic acid require additional enzymes? How does the presence of a carbon-carbon double bond change the total number of ATP that can be produced?

Answer 1

Dear Student,

1. To find no. of moles of ATP synthesized from one mole of CH₃( CH₂ )₂₂ COOH i.e Lignoceric Acid.

Formula for calculating no. of moles of ATP is as follows:

(4+C_I) x nC_I + (4+C_LT) x nC_LT +(4+C_RT) x nC_RT + ( 2.5 x n ) - 3 = N

Note that the above formula is for even numbered satuarated fatty acids.

Where,

C_I, C_LT and C_RT are the oxidation states of the internal, left terminal and right terminal

carbons, respectively .

n is the number of carbons.

nC_I, nC_LT and nC_RT are the number of internal, left terminal and right terminal carbons, respectively.

N is the number of ATP molecules generated.

No. of moles of ATP produced from one mole of CH₃( CH₂ )₂₂ COOH is as follows:

(4+2) x 22 + (4+3) x 1 + (4-3) x 1 + (2.5 x 24) - 3 = 197

Therefore, 197 moles of ATP is produced from one mole of CH₃( CH₂ )₂₂ COOH.

2. Most of the fatty acids in the triacyl glycerols and phospholipids of animals and plants are unsatuarated having one or more double bonds. These bonds are in the cis configuration and cannot be acted upon by enoyl-CoA hydrotase, the enzyme catalysing the addition of H₂O to the trans double bond of the ² eonyl-CoA generated during beta-oxidation. Two auxillary enzymes are needed for beta-oxidation of the common unsatuarated fatty acids like oleic acid are an isomarase and reductase.

Therefore, oxidation of oleic acid requires additional enzyme to complete the process of beta-oxidation.

3. Unsaturated fatty acids have one or more double bonds between carbon atoms.

Pairs of carbon atoms connected by double bonds can be saturated by adding hydrogen atoms to them, converting the double bonds to single bonds. Therefore, the double bonds are called unsaturated.

The two carbon atoms in the chain that are bound next to either side of the double bond can occur in a cis or trans configuration.

cis configuration:

A cis configuration means that the two hydrogen atoms adjacent to the double bond stick out on the same side of the chain.

The rigidity of the double bond freezes its conformation and, in the case of the cis isomer, causes the chain to bend and restricts the conformational freedom of the fatty acid.

The more double bonds the chain is in the cis configuration with less flexibility..

When a chain has many cis bonds, it becomes quite curved in its most accessible conformations.

For example, oleic acid, with one double bond, has a "kink" in it, whereas linoleic acid, with two double bonds, has a more pronounced bend.

Alpha-linolenic acid, with three double bonds, favors a hooked shape.

The effect of this is that, in restricted environments, such as when fatty acids are part of a phospholipid in a lipid bilayer, or triglycerides in lipid droplets, cis bonds limit the ability of fatty acids to be closely packed, and therefore can affect the melting temperature of the membrane or of the fat.

trans configuration:

A trans configuration, by contrast, means that the adjacent two hydrogen atoms lie on opposite sides of the chain.

As a result, they do not cause the chain to bend much, and their shape is similar to straight saturated fatty acids.

In most naturally occurring unsaturated fatty acids, each double bond has three n carbon atoms after it.

In this way, the presence of carbon - carbon double bond change the total number of ATP produced during the synthesis of unsatuarated fatty acids.