All posts by caroline01pd2014

Fun in the Sun

I got my first sunburn this summer (ouch) because I forgot to put on sunscreen. Actually, I pretty much forgot to use sun protectant the whole summer. That got me thinking about sunscreen. It’s just something that we rub onto our bodies, so how does it protect our skin? So in this post I’m going to investigate how sunscreen works, why it’s important to protect your skin from the sun, and how to do so.

The reason we need to protect our skin is because of the UV rays that are present in sunlight. UV rays come in wavelengths from 10nm to 400nm, but there are 3 main categories: UVA (315-400nm), UVB (280-315nm), and UVC (100-280nm). UV radiation has “low penetration” so its effects are mainly limited to the skin. (Encyclopædia Britannica, 2013)

(Skin Cancer Foundation, 2013) – diagram of UV ray penetration of skin

UVC rays are completely absorbed by the Earth’s atmosphere, so we don’t need to worry about that. It’s the UVA and UVB rays that cause trouble. UVB rays are the ones responsible for sunburns and suntans. (Everyday Mysteries: Fun Science Facts from the Library of Congress, 2010) UVA rays, since they have a longer wavelength, penetrate deeper and are the main cause of wrinkles and age spots. (Bytesize Science, 2012) UVA rays can also penetrate through clouds and glass, and 99% of the UV rays that reach the Earth’s surface are UVA rays. (Encyclopædia Britannica, 2013) Both UVA and UVB rays can cause skin cancer. (US Food and Drug Administraton, 2011) Also, sun exposure is responsible for 90% of wrinkles! (Youtube, 2013)

To protect ourselves from these UV rays, sunscreens were invented. There are two types of sun protectants available: chemical and physical sunscreens. Physical sunscreens, also known as inorganic sunscreens, are made out of nanoparticles that are approximately 100nm. They act as tiny reflectors on the skin to deflect and scatter the UV rays that shine onto our skin. (PBS Newshour, 2010) The large particle size is also what attributes to the “white cast” look of sunscreen on the skin. ( Chemistry, n.d.) Typical ingredients in physical sunscreens are titanium dioxide and zinc oxide.

physical sunscreen

(Bytesize Science, 2012) – structures of titanium dioxide and zinc oxide

Chemical sunscreens, also known as organic sunscreens, are much smaller in size, around 40-50nm. The small sizes of the nanoparticles allow it to be more transparent than physical sunscreens. (PBS Newshour, 2010) The most common ingredients in chemical sunscreens are octinoxate and avobenzone. (Bytesize Science, 2012)

chemical sunscreen

(Bytesize Science, 2012) – skeletal structure of octinoxate and avobenzone

Unlike physical sunscreen, chemical sunscreens protect the skin by absorbing the UV rays instead of reflecting it. The molecules in the sunscreen absorb the high-energy UV photons, and the electrons become “excited.” When the molecule returns to its original state, the energy it absorbed is released as insignificant amounts of heat. This process can be done more than once, in a cycle. (Nonprescription Drug Manufacturers Association and Cosmetic, Toiletry, And Fragrance Association, 1998)

Yikes, those UV rays don’t sound nice at all. In the interest of having younger looking skin, not getting a nasty sunburn, and preventing skin cancer, protecting our skin from the sun is a must. Physical sunscreens can only defend our skin from UVB rays, but chemical sunscreens can protect our skin from both. So when buying sunscreen, look for products that are labeled “broad spectrum” or have a PA value because those indicate both UVB and UVA protection. (Youtube, 2013)

(Youngerberg, 2013) – sunblock that have UVA and UVB protection

SPF, which stands for “sun protection factor,” can be a useful way of determining the effects of sunscreen. If your skin can stand 10 minutes in the sun without burning, then a SPF of 30 will allow your skin to be out in the sun for 30×10, or 300 minutes (5 hours), before burning. ( Chemistry, 2010)  Keep in mind that most people don’t put on enough sunscreen (a shot glass worth, or 45mL, of sunscreen is what’s recommended to cover your body), and sweat and water can make the sunscreen less effective, so it is important to reapply sunscreen often (around every 2 hours if you’re active).

It seems that I’ve found the fountain of youth – sunscreen! The next time you’re out in the sun, remember to protect yourself from those pesky UV rays, and do yourself a favor by putting on sunscreen. You’ll thank yourself when you’re older!

References Chemistry (n.d.). How Does Sunscreen Work?. [online] Retrieved from: [Accessed: 19 Sep 2013]. Chemistry (2010). How to Choose the Best Sunscreen. [online] Retrieved from: [Accessed: 19 Sep 2013]. Pediatrics (2010). SPF – Sun Protection Factor and Sunscreen. [online] Retrieved from: [Accessed: 19 Sep 2013].

Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. Available at: [Accessed: 19 Sep 2013].

Discovery Fit and Health (n.d.). What do SPF numbers mean?. [online] Retrieved from: [Accessed: 19 Sep 2013].

Everyday Mysteries: Fun Science Facts from the Library of Congress (2010). How does sunscreen work?. [online] Retrieved from: [Accessed: 19 Sep 2013].

Gizmodo (2013). How Sunscreen Works (And Why You’re Wrong About It). [online] Retrieved from: [Accessed: 19 Sep 2013].

Live Science (2010). How Does Sunscreen Work?. [online] Retrieved from: [Accessed: 19 Sep 2013].

Nonprescription Drug Manufacturers Association and Cosmetic, Toiletry, And Fragrance Association (1998). Tentative Final Monograph for OTC Sunscreen. [e-book] Food and Drug Administration. Available through: [Accessed: 19 Sep 2013].

PBS Newsroom (2010). Just Ask: How Does Sunscreen Work?. [online] Retrieved from: [Accessed: 19 Sep 2013].

Science & Engineering News (2002). C&EN: WHAT’S THAT STUFF? – SUNSCREENS. [online] Retrieved from: [Accessed: 19 Sep 2013].

ultraviolet radiation. (2013). In Encyclopædia Britannica. Retrieved from

US Food and Drug Administration (2011). How Sunscreen Works. Available at: [Accessed: 19 Sep 2013].

Youtube (2013). The Ultimate Guide to Sunscreen. Available at: [Accessed: 19 Sep 2013].


Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. [image online] Available at: [Accessed: 19 Sep 2013].

Bytesize Science (2012). Repelling the Rays: The Chemistry of Sunscreen – Bytesize Science. [image online] Available at: [Accessed: 19 Sep 2013].

Skin Cancer Foundation (2013). Untitled. [image online] Available at: [Accessed: 22 Sep 2013].

Youngerberg, E. (2013). Untitled. [image online] Available at: [Accessed: 22 Sep 2013].

Brain Chemistry

I decided to take AP Language and Composition this year, and one of my summer assignments was to write a book report on any of the books in the recommended reading list. I chose the book The Man Who Mistook His Wife for a Hat by the neurologist Oliver Sacks, because it was one of the most compelling titles out of the bunch. When I started reading, I assumed that this story was a collection of accounts of cases of different mental disorders, which it turned out to be, but I was surprised to find there were some chemistry related aspects to it as well.

In one of the essays, “Witty Ticcy Ray,” Sacks recounted his encounter with a man, named Ray, who had a severe form of Tourette’s, a rare inherited neurological disorder that causes a person to experience frequent “tics” or spasms. (Encyclopædia Britannica, 2013) These tics result from “an excess of exciter transmitters in the brain, especially the transmitter dopamine (C8H11NO2).” (Sacks, 1985)


(Harbin, 2008) – skeletal formula dopamine

Dopamine is a neurotransmitter, which is any group of chemical agents released by neurons (nerve cells) to stimulate neighboring neurons, allowing impulses to be passed from one cell to the next throughout the nervous system. (Encyclopædia Britannica, 2013)


(US National Institutes of Health, 2009) – impulse transmission in synapse

To treat his Tourette’s, his doctor, Sacks, prescribed haloperidol, otherwise known as Haldol, a drug that inhibits the formation of dopamine in his brain.


(Fvasconcellos, 2007) – Skeletal formula of haloperidol

To me, one of the most interesting parts of the essay was Sack’s juxtaposition of Tourette’s and Parkinson’s disease. Where Tourette’s disease is an excess of dopamine, Parkinson’s disease is a lack of it. Parkinson’s is characterized by “muscle rigidity, difficulty and slowness in movement,” the opposite of the hyperactivity that characterizes Tourette’s. (Encyclopædia Britannica, 2013) In an analogy, having Tourette’s would be as if running at the speed of a cheetah, and having Parkinson’s would be as if crawling at the pace of a snail (although this reflects the more extreme cases of the diseases).

In both of these diseases, the causes of the abnormal dopamine production seems to originate from the “the thalamus, hypothalamus, limbic system and amygdala, where the basic affective and instinctual determinants of personality are lodged.” (Sacks, 1985)


(San Diego State University, n.d.) – Brain diagram

The lack of dopamine in a Parkinson’s patient is due to the loss of dopaminergic neurons that normally synthesize and use dopamine to communicate with other neurons in parts of the brain that control and regulate motor function.  To treat Parkinson’s, L-Dopa is given. (Encyclopædia Britannica, 2013)

An organic compound, L-Dopa (L-3,4-dihydroxyphenylalanine; C9H11NO4), also known as levodopa, is a precursor (in biochemistry, a compound that participates in a chemical reaction within a cell) to dopamine, and is able to cross the protective blood-brain barrier (a filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances). (Longe, 2006) Once L-Dopa is in the central nervous system, it is decarboxylated (the removal of the carboxyl (-COOH) group) into dopamine by the enzyme dopa decarboxylase (DDC), a catalyst, and pyridoxal phosphate (vitamin B6). (Porter, 2009) It then increases dopamine concentrations to “awaken” motor senses and restore the physical abilities of the Parkinson’s patients.


(NEUROtiker, 2007) – skeletal formulas and reactions of L-Dopa using biosynthesis

Sacks observed that his dopamine-deficient patients, when first introduced to L-Dopa, “were ‘awakened’ from stupor to health” and exhibited “wild excitements, violent impulses, often combined with a weird, antic humor.” (Sacks, 1985)

Although I do not know anyone who has Parkinson’s, I know that there is an estimated 10 million people worldwide that live with Parkinson’s, and approximately 60,000 people are diagnosed with it each year in the United States alone. (Parkinson’s Disease Foundation, 2013) Those numbers are scary, but my findings should be able to comfort those who have been affected by Parkinson’s. Whether a friend, family member, or themselves has Parkinson’s, I hope they will feel better knowing that there are methods of treatment that can help Parkinson’s patients lead relatively normal lives.

I did, however,  have a classmate in 8th grade who hit their head on the ground during P.E. and started experiencing restlessness and tics that he could not control. After my research, I can infer that that boy might have hit a certain part of his head to create an excess production of dopamine in his brain, and a possible treatment would be a prescription of Haldol, or another dopamine inhibiting drug.

I used to think that “something just went wrong with the brain” when thinking about neurological disorders, but my findings tell me that they are nothing to be afraid of, and that there are logical reasons behind these diseases. The advancement of medicine has come very far, and in the future I am sure there will be even greater advancements in this field. For example, a research project working on targeting dopamine-controlling drugs to the specific, affected part of the brain is currently underway. For more information on this study , here is a very interesting TedTalk on “brain chemistry.”


Human disease. (n.d.). Encyclopedia – Britannica Online Encyclopedia. Retrieved March 12, 2013, from

Levodopa. (n.d.). Encyclopedia – Britannica Online Encyclopedia. Retrieved March 12, 2013, from

Longe, J. L. (2006). The Gale encyclopedia of medicine (3rd ed.). Detroit: Thomson Gale.

Porter, C. (2009, December 2). Chemistry of L-Dopa. Levodopa. Retrieved March 12, 2013, from

Sacks, O. W. (1985). The man who mistook his wife for a hat and other clinical tales. New York: Summit Books.

Statistics on Parkinson’s. (n.d.). Parkinson’s Disease Foundation. Retrieved March 12, 2013, from

Tourette syndrome. (n.d.). Encyclopedia – Britannica Online Encyclopedia. Retrieved March 12, 2013, from

dopamine. (n.d.). Encyclopedia – Britannica Online Encyclopedia. Retrieved March 12, 2013, from

neurotransmitter. (n.d.). Encyclopedia – Britannica Online Encyclopedia. Retrieved March 12, 2013, from


San Diego State University (2013). Limbic System. [image online] Available at: [Accessed: March 12, 2013].

TedTalks (2013). David Anderson: Your brain is more than a bag of chemicals. Available at: [Accessed: March 13, 2013].

Unknown. (2013). Dopamine. [image online] Available at: [Accessed: March 12, 2013].

Unknown. (2013). Haloperidol. [image online] Available at: [Accessed: March 12, 2013].

Unknown. (2013). Catecholamines biosynthesis. [image online] Available at: [Accessed: March 13, 2013].

US National Institutes of Health (2013). Chemical synapse schema cropped. [image online] Available at: [Accessed: March 13, 2013].