On pages 82-83, Dr. Moalem describes how raw habanero peppers have a burning chemical called capsaicin. This relates to Big Idea 1, the process of evolution drives the diversity and unity of life, because this capsaicin has evolved to affect mammals but not birds.
Capsaicin is characterized as a sticky poison. Describe what this means, how it affects mammals, the best way to ease and prevent these effects in mammals, and how it affects birds. Also, explain why affecting birds and mammals differently is a selective advantage for the habanero peppers. Besides the burning sensation, what other effects can capsaicin can have on mammals’ bodies in large quantities?
In the chapter “Hey, Bud, Can You Do Me a Fava?”, Dr. Moalem describes the effects of capsaicin of raw habanero peppers on mammals and birds. Capsaicin is a colorless, odorless, and hydrophobic compound that “adheres to mucous membranes” (82). Mucous membranes are layers of tissue that line the body specifically the respiratory and digestive tract. The capsaicin creates a burning sensation which is why mammals are sensitive to the compound because it irritates nerve fibers that sense pain and heat. However, unlike mammals birds are not sensitive to the compound and are therefore unaffected by it. This is because the TRPV1 channel (contains receptors for capsaicin) in which the compound binds to does not respond to capsaicin in birds which allows the birds to consume the seeds of the peppers and allow for the seeds to pass through the digestive tract and eventually germinate once they leave the bird’s body. Unfortunately mammals that are sensitive to capsaicin can only alleviate the effects. Consuming fat allows for the the removal of capsaicin from the mucous membrane. We learned in a previous unit that fat (triglyceride) is composed of three fatty acids connected a glycerol molecule. The fatty acids are composed of long chains of carbon with a hydroxyl group making the fat nonpolar and thus hydrophobic. This allows it to remove the capsaicin which is also hydrophobic and eventually cool down the “burning”.
ReplyDeleteThe habanero peppers, like all living things, want to survive and reproduce. This affects their interactions with other organisms which is related to Big Idea 4. Mammals can destroy the seeds of the peppers in their digestive system. A simple example of this is when they consume the peppers, the seeds can be grounded with their teeth. The capsaicin acts as a deterrent to keep mammals away because they cannot help plants disperse their seeds as effectively as birds can. Birds in this case have a selective advantage because they are not affected by the capsaicin. This is beneficial for the the plants because the birds help them with seed dispersal and the birds as well because the peppers serve as food for them.
Other than a burning sensation, studies have found that capsaicin can have embryological effects. In an experiment using pregnant rats, results showed that there were delays in skeletal formation for those exposed to the irritant. And although more research needs to be conducted, Dr. Moalem describes that capsaicin can also “cause selective degeneration of some types of neurons” (83).
Faith Teodoro (fteodor4@students.d125.org)
Source:
(http://www.livestrong.com/article/356068-the-toxicity-of-capsaicin/)
In an experiment with rats that have been treated with capsaicin, a sticky poison common in peppers, the rats had experienced slower growth rates compared to the control. In addition, when compared to controls, the capsaicin treated rats mated less frequently. And the males that had been treated with capsaicin that mated with untreated females, produced fewer offspring than males that were untreated. The reproductive system of capsaicin treated rats was functioning normally. What seemed to be the problem was when the rats treated with capsaicin, neurohormonal reflex was not occurring. The neurohormonal reflex is used to release hormones needed for reproduction in both females and males. The capsaicin may have resulted in lower pregnancies due to the fact that the neurohormonal reflex was inhibited. The neurohormonal reflexes may have fibers that are sensitive to the poison. (http://www.ncbi.nlm.nih.gov/pubmed/6493363) This relates to big idea four, biological systems interact, and these systems and their interactions possess complex properties, since the rats are reacting to the capsaicin added to their environment.
ReplyDeleteOne way that capsaicin affects rat fetus growth is by selectively damaging small unmyelinated primary sensory neurons. This damage is permanent and causes neuronal damage. Another experiment was conducted to see how adult rats would be affected by the exposure to capsaicin. In the adult rats, it was concluded that the capsaicin damaged vagal sensory neurons. The damage was permanent. (http://onlinelibrary.wiley.com/doi/10.1002/cne.902710109/abstract) This could be due to that capsaicin may interfere with ligand –gated channels that open or close due to interactions with chemicals.
Capsaicin can have benefits, such as pain reduction, but during pregnancies, it is not advised that a women expecting should not use capsaicin creams. The FDA has put capsaicin into a category B, which means it has a low risk for causing pregnancy complications, but it is still not advised. Mothers who are breast-feeding should not use capsaicin as it is excreted into breast milk. The effect of babies drinking breast milk with capsaicin has not been tested yet. (http://www.drugs.com/pregnancy/capsaicin-topical.html)
Lily Barghi (lbarghi4@students.d125.org)
ReplyDeleteOn pg 82, Capsaicin is described as a sticky poison because “it adheres to mucous membranes”, which is why your eyes burned if you ever rubbed them after handling peppers. Its stickiness acts to prevent capsaicin from easily dissolving in water. “It is what puts the heat or pungency in chiles. It is a compound that is insoluble in water, tasteless and odorless.” (http://faq.gardenweb.com/faq/lists/pepper/2002075348029538.html)
Mammals are very sensitive to it because it tickles the nerve fibers that sense pain and heat. So mammals that are sensitive to capsaicin can only alleviate the effects. However, birds are not sensitive to the Capsaicin in peppers. The reason for this is like Faith said, “because the TRPV1 channel (contains receptors for capsaicin) in which the compound binds to does not respond to capsaicin in birds which allows the birds to consume the seeds of the peppers and allow for the seeds to pass through the digestive tract and eventually germinate once they leave the bird’s body.” And because they aren’t sensitive, their bodies don’t destroy chili seeds when they eat chili peppers. So the mammals just leave the peppers for the birds.
This is a selective advantage for the peppers because the digestive systems of mammals destroy the small seeds. Rodents like mice would normally be drawn to the fruits of chili plants avoid them because they can’t take the heat.
So not only does Capsaicin cause a burning sensation, but it can actually cause selective degeneration of some types of neurons. So in large quantities, hot peppers can be very dangerous. So in locations like Sri Lanka where hot peppers are a staple in people’s diets, there is a much higher rate of stomach cancer.
Josh Baker (jbaker3@students.d125.org)