AP Biology class blog for discussing current research in Biology

Author: garfboxylgroup

Why are Blueberries Blue?

Have you ever wondered how certain fruits are such vibrant colors? Scientists globally have also pondered such characteristics. Some people think that objects obtain their colors by simply having the pigment inside. However, how our eyes perceive color is much more complicated than simply seeing the pigmentation.

Recently, research has been conducted on the color of blueberries. Blueberries are considered to be a “bloom” fruit, in that it has an epicuticular wax layer and dark pigmentation. This color does not come from smushing the fruit and watching the juice emerge, which led researchers to wonder where exactly it does come from. Researchers have discovered that blueberries are covered by a thin, waxy coating that is two microns thick. The researchers discovered this by removing the waxy layer and recrystallizing it to view the particles within the layer itself.

Within this layer, there are scattered particles in a random crystalline structure that reflect blue and UV light. Photons of light have certain pigments, and only a few of which are visible to humans. The photo below depicts which light is visible to humans. It is also notable that the pigment in blueberries reflects UV light, which is visible to birds.

FIO117: Figure 8.1

This directly relates to our AP Bio Photosynthesis Unit. In this unit we learned the reason why leaves are green. This is because leaves contain certain pigments (one being chlorophyll a) that absorb all wavelengths of light except for green, which is reflected.

Additionally, we learned in AP Bio that leaves are surrounded by a non-polar, waxy substance. This is the same on blueberries. It is interesting that learn that water will not easily penetrate through the skin of leaves as well as certain fruits due to the repulsion of non-polar and polar substances.

Do you know of any other epicuticular fruits? Can we investigate their pigmentation as well?

New Injection Provides Hope for Regaining Smell Following COVID-19 Infection

Did you or someone you know ever contract COVID-19 and lose your sense of taste or smell? This is called Parosmia. There are people on social media who have tried to theorize ways to regain the ability to smell normally. For example, burning an orange peel. However, if your nasal cavity is damaged, regardless of the strong orange aroma, it may be believed that you will not be able to regain your sense of smell.

So, how was your nose damaged in the first place? The olfactory system contains a zone that detects scents towards the top of the nasal cavity. When molecules diffuse up into the nose, they dock in receptor proteins which ultimately initiates a cascade to create a cellular response. Hence, we are able to smell aromatic molecules.

When someone is infected with the SARS-CoV2 virus, the olfactory epithelial cells are damaged. Doctors have analyzed singular cells following a biopsy in order to examine the effect of the virus on healthy cells.  They were able to conclude that the body ignited a innate immunity response, in which swelling occurred where the nerve endings are located. While in some cases the swelling decreased following the innate response, other times, the swelling remained and damaged the tissue.

Novel Coronavirus SARS-CoV-2

This can be explained by what we have learned in AP Biology. During an innate immune response, cells release histamines. These dilate blood vessels, while macrophages secrete cytokines. Cytokines attract phagocytes that allow the infected cells and pathogens to be destroyed. The proteins that attempt to interfere with the viruses cause more histamine to be released and overall more swelling. Therefore, the nasal cavity can remain damaged.

However, new research has found that an injection just might help patients with long COVID symptoms to regain their sense of smell. According to Dr. Adam Zoga, one way that patients have begun to smell again is by injecting stellate ganglion blocks into the neck on either side of the voice box. This reaches the stellate ganglia which contains nerve bundles that control your body’s fight-or-flight responses, known as the sympathetic nervous system. Patients also received a steroid injection to decrease swelling.

The patients that participated in the study did not all benefit from it. However, 22 of the 37 that followed up with administrators following the trial injection noticed improvements in one week. Dr. Leigh Sowerby analyzed this data and theorizes that this may work to treat Parosmia because the sense of smell is affected when the sympathetic nervous system is overactive. He believes that this injection “resets” the nervous system, allowing the nerve bundles to return to normal and patients to regain their sense of smell. However, because only 37 of the original 54 patients followed up after the injections, and there was no control group, researchers cannot further extended this claim.

Why Does our Hair Flow the Way it Does?

Do you ever wonder why your hair always naturally parts the same way? Our hair patterns can be described as our “hair whorl.” This denotes the direction in which the hair follicles orient themselves, as well as the number of times the hair rotates in a circular pattern. This can be either a single or double whorl. While this physical characteristic maybe be obvious to the naked eye, it is unclear why these patterns initially occur.

Boy with shiny short hair and whorls, rear view

In a recent study, the National Survey of Physical Traits cohort came together to understand whether or not our hair patterns could be determined by genetic characteristics. In China, Lead Investigator Sijia Wang determined that hair whorl can be a result of four genetic variances, also known as a polygenic inheritance. These variances occur at 7p21.3, 5q33.2, 7q33, and 14q32.13, which are specific locations on a DNA sequence. These variances affect hair patterns due to both cell polarity as well as cranial neural tube closure and extension.

This relates to AP Biology due to the effect of cell polarity on the hair whorl. In class we learned that non-polar (hydrophobic) molecules will move away from polar molecules. Hair cells are classified as epithelial cells, meaning they exist on the outer-most layer of our skin’s surface. They are polarized in sheet known as the planar cell polarity (PCP). The author’s logic makes sense in that a pattern will occur in the hairline if the polar molecules are moving away from those that are non-polar, or vice versa.

Blausen 0806 Skin RootHairPlexus

Additionally, because the whorls can be associated with neural tube closures and growths, it was believed that abnormally placed or shaped whorls can be related to a neurological deficit. However, Dr. Wang’s research did not confirm whether or not this was true.

Now it’s your turn — can you find your hair whorl?


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