Thanksgiving Day

Americans commemorate today the Thanksgiving Day.

This is a very specific holiday for the United States. Anyway, if we think about it, and beyond the Mayflower’s Peregrines, the Indians and the turkey…wouldn’t it be very good to have all over the world a day devoted to give thanks for everything we have accomplished?  We can complain the whole rest of the year!, but let’s have a day just to say…Thanks God! and thanks to my family!, and thanks to everybody for helping me during my life!











Some beautiful vintage post cards about Thanksgiving Day:







Biochemistry Question CM-21


A 13 year-old patient with Type I diabetes mellitus, home alone,  takes an insulin injection before lunch but then he gets concentrated in a videogame he is playing and does not eat. Approximately 3 hours later, he becomes sweat, shaky and confused. These symptoms have appeared as a consequence of:


a) increased glucagon release from the pancreas


b) decreased glucagon release from the pancreas


c) increased insulin  release from the pancreas


d) decreased insulin release from the pancreas


e) high sugar levels in blood


f) low sugar levels in blood



Inhibitors of the Electron Transport Chain


Answer to Question B-09


As described in a former post, the inhibitors of the Electron Transport Chain are substances that bind to some of the components of the ETC blocking its ability to change in a reversible form from an oxidized state to a reduced state.


This inhibition results in the accumulation of reduced forms before the inhibitor point, and oxidized forms of the components of the ETC downstream (ahead) the inhibition point.



Since energy is not released, the synthesis of ATP also stops. The most important known inhibitors of the ETC are Amytal, Rotenone, Antimycin A, CO, Sodium Azide, and Cyanides.


Amytal, a barbiturate, and Rotenone, a plant product used as insecticide and pesticide, block the ETC between NADH dehydrogenase (Complex I) and CoQ.


Consequently, they prevent the utilization of NADH as a substrate. On the contrary, electron flow resulting from the oxidation of Complex II is not affected, because these electrons enter through QH2, beyond the block.


The effect of Amytal has been observed in vitro, since the intoxication with amytal and other barbiturates in vivo affect mainly the CNS by acting on GABA-sensitive ion channels, an effect not related to the action of Amytal on Complex I.


Rotenone intoxications are very rare. In facts, some human tribes used to catch fishes by spreading plant extracts containing rotenone in the water, and this substance was easily absorbed by the fishes through the gills. These fishes were eaten later without notable side effects in humans, since rotenone is absorbed very difficult by the gastrointestinal tract. Usually, when taken in a concentrated form, irritating action in mucoses causes vomits.


It is interesting to note that Rotenone and MPTP (a neurotoxin), when administered in vein,  cause at the same time interference with the functioning of Complex I and a Parkinson-like disease. These substances affect primary neurons in substancia nigra; apparently the sequence is: impairment of Complex I, impairment of mitochondria metabolism, accumulation of free radicals, cell death, release of toxic compounds and destruction of other cells.


Antimycin A is an antibiotic produced by Streptomyces griseous that has been used as a piscicide for the control of some fish species. Antymicine A interferes with electron flow from cytochrome bH in Complex III (Q-cytochrome c oxidoreductase).  In the presence of this substance, cytochrome bH can be reduced but not oxidized, consequently,  in the presence of antimycin A cytochrome c remains oxidized, as do the cytochromes a and a3 that are ahead.


Carbon monoxide (CO) is responsible for more than 50 % of death by poisoning worldwide. It is colorless and odorless; high levels can result from incomplete combustion of fuels: engine and furnace exhausts are important sources. Tobacco smoking increases CarboxyHb levels.


Carbon monoxide intoxication causes impaired oxygen delivery and utilization at the cellular level. The affinity of Hb for CO is almost 300 times higher than for Oxygen. An environment in which there is 100 ppm of CO is enough to form 16 % carboxyhemoglobin. The situation is worsen since the binding of CO to one of the Hem groups of Hemoglobin increases the affinity of the other three Hem groups for Oxygen, so the delivery of Oxygen to  tissues is very affected. The brain and the heart, that has a high Oxygen consumption, are the most affected. Myoglobin has even a greater affinity for CO than Hemoglobin. As a consequence of the binding of CO to these molecules, the heart functioning is very impaired and the patient presents sever hypotension. As described above, this intoxication is an important cause of death worldwide.


The affinity of respiratory chain components for CO is lower than for Oxygen,

but since the clinical status does not correlate very well with the carboxyhemoglobin levels, it is considered that the inhibition of Cytochrome Oxidase by CO also plays a role in CO intoxication. CO binds to the reduced form of iron in Hem groups (Fe++) in cytochrome Oxidase


On the contrary, in cyanide intoxication the inhibition of the respiratory chain has a primary role. Intoxication by cyanide can be seen relatively frequent in patients with smoke inhalation from residential or industrial fires. Also in persons related professionally with cyanide or derivatives in certain industries.  Intentional poisoning can be seen in suicidal persons with access to cyanide compounds. Cyanide affects practically all metalloenzymes, but its principal toxicity derives from the binding to the Fe+++ in the Hem groups in cytochrome Oxidase, inhibiting the functioning of the Electron Transport Chain. As a consequence, redox reactions in the respiratory chain will stop, energy will not be released, proton pumps will not function, so they will not return through Complex V, and the production of ATP will cease (Related question here).


Azides have an action on the respiratory chain very similar to cyanide, inhibiting the Hem groups of cytochromes in Cytochrome Oxidase (Complex IV). Azides are used as propellants in airbags, in detonant (explosive) industry and as preservative of sera an reagents. Some cases of azide intoxication in humans have been reported.


You can find more information about these inhibitors of the Electron Transport Chain in these links:


Antimycin A: toxicity, ecological toxicity and regulatory information



Risk assessment for Piscicidal Formulations of Antimycin


Leybell, I: Toxicity: Cyanide


Cyanide poisoning



Azide Toxicity


Sodium Azide Toxicity effects


Shochat, G.N.: Toxicity, Carbon Monoxide



50 000 views: Let’s have a Biochemistry party!


 OK, so the blog arrived to 50 000 views today (exactly, 50 080 in the moment I am writing this post).


To arrive to this number of visits makes me happy since I began this blog just in March of this year and the topics that have been discussed are not exactly about popular issues or popular culture, or election or sports.


I appreciate the reception to this blog and I would like to encourage comments, questions, additional information, related to the posts that I have written. Also any suggestion about future posts.


To celebrate arriving to this number of visits, let’s have a party… inside the boundaries of science:



Making ATP



If you’re not part of the solution, you’re part of the precipitate!”


“Do you have mole problems? If so, call Avogadro at 602-1023.”


Q: How did the football cheerleader define hydrophobic on her chemistry exam?
A: Fear of utility bills


Biology is the only science in which multiplication is the same thing as division


At NIH (National Institute of Health), there is a sign on the door of a microbiology lab that reads “STAPH ONLY!”



Another biochemical musical theme (Biochemic)



A miracle drug is one that has now the same price as last year.


Customer gets a topical cream. Direction: apply locally two times a day.
Customer says to the pharmacist: “I can’t apply locally, I’m going overseas.”


Doctor: “Nurse, how is that little boy doing, the one who swallowed ten quarters?”
Nurse: “No change yet.”


What’s the difference between a nurse and a nun?
A nun only serves one God



Cell rap



Dentist: I have to pull the aching tooth, but don’t worry it will take just five minutes.
Patient: And how much will it cost?
Dentist: It’s $90.00.
Patient: $90.00 for just a few minutes work???
Dentist: I can extract it very slowly if you like.


“Doctor, Doctor, You’ve got to help me – I just can’t stop my hands shaking!”
“Do you drink a lot?”
“Not really – I spill most of it!”


A woman, calling Mount Sinai Hospital, said, “Hello, I want to know if a patient is getting better.”
The voice on the other end of the line said, “What is the patient’s name and room number?”
She said, “Yes, darling! She’s Sarah Finkel, in Room 302.”
He said, “Oh, yes. Mrs. Finkel is doing very well. In fact, she’s had two full meals, her blood pressure is fine, she’s going to be taken off the heart monitor in a couple of hours and if she continues this improvement, Dr. Cohen is going to send her home Tuesday.”
The woman said, “Thank God! That’s wonderful! Oh! That’s fantastic! That’s wonderful news!”
The man on the phone said, “From your enthusiasm, I take it you must be a close family member or a very close friend!”
She said, “I’m Sarah Finkel in 302! Cohen, my doctor, doesn’t tell me a word!”


If it is dry – add moist; if it is moisten – add dryness. Congratulations, now you are a dermatologist.


What is a double-blind study?
Two orthopedists reading an electrocardiogram.


Neurotics build castles in the sky.
Psychotics live in them.
Psychiatrists collect the rent.


How many doctors does it take to change a light bulb?
That depends on whether it has health insurance.


How many surgeons does it take to change a light bulb?

Two, since they are going to remove also the socket as you are not using it now



And for finishing this party, the already famous song of Biochemist for a Better PCR:


The PCR song





How to calculate QUICKLY the energetic balance of the total oxidation of a fatty acid


The basis for the calculation and how to do it have been explained in detail in other post.


Anyway, since time is an issue in exams, some readers are interested in knowing a method of doing the calculation in a real fast way.


For obtaining a quick answer when calculating the energetic balance of the total oxidation of a fatty acid (and also for verifying your answers if you use some other method of calculation) you can apply these formulas:


a) If your course use for the reduced cofactors these energetic yields

NADH.H+ = 2.5 ATP

FADH2 = 1.5 ATP


Use this formula:


[(n/2) -1] x (14) +8 = Number of ATP formed


Where n= Number of carbons




Balance of the total oxidation of palmitic acid (16 carbons):

(16/2)-1] x (14) +8 = 106 ATP


b) If the equivalence used for the energetic yields in your course are:




Then apply this formula:


[(n/2) -1] x 17 +10 = Number of ATP formed


For the total oxidation of palmitic acid, following the former energetic yielding criteria:


[(16/2)-1] x 17 + 10 = 129 ATP


Thanks for the questions and comments!



Vitamin K and Newborns


Given that:


– Vitamin K is not easily transported from the mother to the fetus through the placenta

– Newborns have sterile intestines and cannot initially synthesize vitamin K.

– Human milk has very low concentrations of vitamin K,


some authors recommends that all newborns receive a single intramuscular dose of Vitamin K, since Vitamin K is a liposoluble vitamin necessary for:


a)     the prevention of oxidative damage


b)     Ca++ and phosphate metabolism


c)      the vision process


d)     the synthesis of some coagulation factors


e)     the differentiation of epithelial cells.