Q: About dry eyes, dry skin…


A 45-year-old, overweight male patient  presents to his physician complaining of dry skin with rash episodes, a sensation of dry eyes and lost of vision, mainly at night.  During  questioning,  he says he lost 60 lbs. during the previous year, following a very strict fat-free diet that he modified from some readings.


Which of the following liposoluble vitamins could be deficient in the patient and causing the above described symptoms?


a)     Vitamin A


b)     Vitamin D


c)      Vitamin E


d)     Vitamin F


e)     Vitamin K



There is Biochemistry also in “Twilight”!

“And Edward was staring at me curiously, that same, familiar edge of frustration even more distinct now in his black eyes.

I stared back, surprised, expecting him to look quickly away. But instead he continued to gaze with probing intensity into my eyes. There was no question of me looking away. My hands started to shake.

“Mr. Cullen?” the teacher called, seeking the answer to a question that I hadn’t heard.

The Krebs Cycle,” Edward answered, seeming reluctant as he turned to look at Mr. Banner.”



Related posts:


Porphyrias at the movies


Total Oxidation of a 17 carbon fatty acid, including oxidation of the resulting Propionyl CoA

Let’s use the basic calculations described in previous posts about this issue:


Beta-oxidation of  fatty acids with an odd number of carbons.


Energetic balance of the total (and I mean total) oxidation of a fatty acid with an odd number of carbons.


Oxidation of a fatty acid with 17 atoms of carbon.



Activation of the fatty acid to Acyl CoA = -2 ATP


Number of rounds in the Beta oxidation

(17/2) -1.5 = 8.5-1.5 = 7

7 rounds x  5 ATP/ round = 35 ATP


Number of units of Acetyl CoA produced = 7 Acetyl CoA

7 Acetyl CoA x 12 ATP/Acetyl CoA  = 84 ATP


Propionyl CoA up to Succinyl CoA = -1ATP


Succinyl CoA up to Malate = 3 ATP


Malate up to Pyruvate (1 NADPH.H+)


Pyruvate up to Acetyl Co A = 3 ATP


Acetyl CoA oxidation in the Krebs Cycle = 12 ATP


Total of ATP (considering the total oxidation of Propionyl CoA converted to Malate and then from Malate to Pyruvate and then from Pyruvate to Acetyl CoA = -2 + 35 +84 -1 + 3 +3 +12 =  134 ATP


In summary  (following the equivalence of  1 NADH.H+ yielding 3 ATP in the Respiratory Chain and 1 FADH2 yielding 2 ATP):


-Calculate the number of rounds of the fatty acid in the Beta-oxidation:

  Number of rounds  = (Number of carbons/2) -1.5


-The number of Acetyl CoA is the same as the number of rounds


-Subtract 2 ATP that were used in the initial activation of the fatty acid.


-Multiply the number of rounds x 5 ATP/round.


-Multiply the number of Acetyl CoA x 12 ATP/Acetyl CoA.


-Add 17 ATP produced in the total oxidation of Propionyl CoA to CO2



To practice this kind of exercise, I suggest that you do the calculations using now  the criteria that considers that each NADH.H+ oxidized in the Respiratory Chain yields 2.5 ATP and each FADH2 yields 1.5 ATP



I am looking forward to see your answers and comments!!!