Passage
Fatty acids (FAs) are lipids that play important roles in cellular function, including energy storage and membrane structure. Most polyunsaturated fatty acids (PUFAs) are made in the body; however, omega-3 alpha-linolenic acid and omega-6 linoleic acid must be obtained from the diet. These two PUFAs are precursors to other omega-3 and omega-6 long-chain FAs that are necessary for physiological processes such as neurological development, normal growth, and immune response. Insufficient omega-3 and omega-6 long-chain FAs can lead to an increase in omega-9 fatty acids such as mead acid, and to essential fatty acid deficiency (EFAD) , which can cause infertility, decreased growth, and increased susceptibility to infection.Total FA levels in plasma and serum can be used to diagnose EFAD. Plasma and serum samples from several individuals were hydrolyzed to release FAs from triacylglycerols and phospholipids. Once isolated, the free FAs were converted to pentafluorobenzyl (PFB) derivatives and separated by gas chromatography (GC) . Total levels of each type of fatty acid were quantified by negative chemical ionization-mass spectrometry (NCI-MS) immediately after GC. NCI is an ionization technique that creates negatively charged ions with little to no fragmentation. The NCI-MS revealed that two of the peaks from GC had the same m/z ratio (Figure 1) . They were both confirmed to be forms of an unsaturated, unbranched 22-carbon FA called omega-9 docosenoic acid.
Figure 1 Selected ion chromatogram of docosenoic acidResearchers have proposed that an elevated ratio of the triene omega-9 mead acid to the tetraene omega-6 arachidonic acid, known as the triene/tetraene (TT) ratio, can signify EFAD. Using GC and NCI-MS, they measured the TT ratio, concentration of mead acid, and individual concentrations of omega-3 and omega-6 FAs in plasma and serum samples from three patients and compared their results to normal ranges. An increased TT ratio and mead acid concentration and decreased omega-3 and omega-6 FA concentrations were observed in the patient samples compared to normal ranges.
Adapted from E. Kish-Trier et al., "Quantitation of total fatty acids in plasma and serum by GC-NCI-MS." Clinical Mass Spectrometry. ©2016 Elsevier.
-Which of the following conclusions is NOT consistent with the results of the patient plasma and serum sample analysis described in the passage?

Question

Passage
Fatty acids (FAs) are lipids that play important roles in cellular function, including energy storage and membrane structure. Most polyunsaturated fatty acids (PUFAs) are made in the body; however, omega-3 alpha-linolenic acid and omega-6 linoleic acid must be obtained from the diet. These two PUFAs are precursors to other omega-3 and omega-6 long-chain FAs that are necessary for physiological processes such as neurological development, normal growth, and immune response. Insufficient omega-3 and omega-6 long-chain FAs can lead to an increase in omega-9 fatty acids such as mead acid, and to essential fatty acid deficiency (EFAD) , which can cause infertility, decreased growth, and increased susceptibility to infection.Total FA levels in plasma and serum can be used to diagnose EFAD. Plasma and serum samples from several individuals were hydrolyzed to release FAs from triacylglycerols and phospholipids. Once isolated, the free FAs were converted to pentafluorobenzyl (PFB) derivatives and separated by gas chromatography (GC) . Total levels of each type of fatty acid were quantified by negative chemical ionization-mass spectrometry (NCI-MS) immediately after GC. NCI is an ionization technique that creates negatively charged ions with little to no fragmentation. The NCI-MS revealed that two of the peaks from GC had the same m/z ratio (Figure 1) . They were both confirmed to be forms of an unsaturated, unbranched 22-carbon FA called omega-9 docosenoic acid.

Figure 1 Selected ion chromatogram of docosenoic acidResearchers have proposed that an elevated ratio of the triene omega-9 mead acid to the tetraene omega-6 arachidonic acid, known as the triene/tetraene (TT) ratio, can signify EFAD. Using GC and NCI-MS, they measured the TT ratio, concentration of mead acid, and individual concentrations of omega-3 and omega-6 FAs in plasma and serum samples from three patients and compared their results to normal ranges. An increased TT ratio and mead acid concentration and decreased omega-3 and omega-6 FA concentrations were observed in the patient samples compared to normal ranges.
Adapted from E. Kish-Trier et al., "Quantitation of total fatty acids in plasma and serum by GC-NCI-MS." Clinical Mass Spectrometry. ©2016 Elsevier.
-Which of the following conclusions is NOT consistent with the results of the patient plasma and serum sample analysis described in the passage?

Quizplus · Accepted Answer

11ecba2d_1297_de11_a3bf_4db15643d446_MD0008_00 The passage states essential fatty acid deficiency (EFAD) is caused by a deficiency in omega-3 and omega-6 long-chain fatty acids (FAs). Omega-3 alpha-linolenic and omega-6 linoleic acids are precursors to long-chain FAs, and must be obtained from the diet. Given that the omega-3 and omega-6 FA concentrations in the patient plasma and serum samples were lower than normal ranges, alpha-linolenic and linoleic acids concentrations should be lower than the normal range (Choice C). Omega-3 and omega-6 FA deficiencies lead to an increase in omega-9 FAs including mead acid, which was the triene used to measure the TT ratio. Because a decrease in omega-3 and omega-6 FA concentrations was observed in the patient plasma and serum samples, a higher than normal mead acid concentration that was higher than normal ranges was also observed in the patient plasma and serum samples (Choice D). The passage also states that an elevated mead acid/arachidonic acid ratio, or TT ratio, is indicative of EFAD. An increased TT ratio was observed in the plasma and serum samples, indicating that the patients likely have EFAD (Choice A). The omega-6 FA concentrations observed in the patient plasma and serum samples were lower than normal ranges, and an increased TT ratio was observed. Arachidonic acid is an omega-6 FA, and an increased concentration of arachidonic acid would decrease the TT ratio rather than increase it because arachidonic acid is in the denominator of the ratio. Therefore, the concentration of arachidonic acid is not expected to be higher than normal. Educational objective: Drawing conclusions based on experimental results requires analysis of given information. The effect that results have on another variable can be applied to make conclusions about what changes should occur to that variable. When given information about how a ratio changes, assess what increases or decreases to cause the ratio to change in the specified way.

Passage Fatty Acids (FAs) Are Lipids That Play Important Roles in in Cellular