The Science of Lying

Here's an excellent video by Hank Green of SciShow on the science of lying!

Everything You've Ever Wanted to Know About Carbohydrates!

Diagram of a glucose molecule.

You've probably heard quite a bit about carbohydrates.  When dieting you avoid them like the plague; they're in pastas, pizzas, and many other delicious Italian dishes.  But what, in fact, is a carbohydrate?  Carbohydrates are defined as molecules that are some form of sugar (either a polymer or monomer).  These sugars are composed of three elements:  Carbon, Hydrogen, and Oxygen in a 1:2:1 ratio. The carbohydrate most commonly found in nature is Glucose, with the molecular formula C6H12O6 (See right).  Carbohydrates perform several key functions for cells.  They store energy and they provide structure for living organisms.  The simplest sugars, such as Glucose, are referred to as monosaccharides.  Two monosaccharides can be combined to form a molecule called a disaccharide.  The process by which this occurs is called dehydration synthesis.  In dehydration synthesis, one monosaccharide donates a hydroxide ion (OH-) and another donates a hydrogen ion (H+).  These two ions form one molecule of H2O.

The result is that the two monosaccharides are held together in a glycosidic linkage.  Many monosaccharides can be combined in this way to form a polysaccharide.  Polysaccharides are the molecules that we usually think of as "carbohydrates".  They are composed of chains that have hundreds or even thousands of monosaccharides joined together via dehydration.  Interestingly enough, these chains can be broken apart using a process named hydrolysis.  Hydrolysis is, in essence, the opposite of dehydration.  In hydrolysis, the bond between two monosaccharides is broken by introducing a water molecule.  Energy is released, and the glycosidic linkage dissipates.  This is how carbohydrates store energy, by creating large polysaccharides when energy is abundant and breaking up the polysaccharides when energy is scarce.  

There are four common types of carbohydrates found in nature, described below:

1.  Starch

Potatoes, a common starch

Starch is an energy storage polysaccharide found in plants, specifically in their granules. (Want to know more about cell parts?  Click here.)  These molecules are spiral shaped, allowing for more efficient and compact storage.  The presence of starch enables a plant to stockpile its excess glucose and use it later for energy.  Starch can be broken apart by both humans and animals for energy.  Starch is, in fact, composed of two distinct substances.  The first is known as amylose.  Amylose, making up 20% of the molecule's composition, is soluble in water and has a linear shape.  Amylopectin makes up the other 80%.  Amylopectin is branched and, for the most part, not able to be dissolved by water.  Examples of starch include corn, rice, and potatoes.  

2. Glycogen

Glycogen is starch's animal counterpart.  Mostly found in the liver and muscle cells, glycogen is essential to an animal's well-being.  Without glycogen, normal body conditions cannot be maintained for long periods of time.  In fact, human beings must eat some kind of food with carbohydrates, otherwise glycogen stores will be depleted and muscle capabilities will be decreased.

3.  Cellulose

A cross-section of wood.

Cellulose provides structure to plants.  It is a straight, unbranched molecule.  Its components are held together by hydrogen bonds and mibrofibrils.  Cellulose is most commonly found in the cell walls of plants, and is the most commonly found organic compound on the planet.  Interestingly, cellulose is a polymer of glucose, with different glycosidic linkages than that of starch.  Hence, it has a flat shape while starch has a helix shape.  Cellulose is the main component in wood.  Some species of animals, such as termites, have special enzymes that enable them to digest this substance, however humans cannot digest it.

4. Chitin

Chitin is the structural carbohydrate found in many animals.  It is present in the exoskeletons of insects, and the cell walls of funguses.  Chiten has beta linkages with nitrogen attachments, creating its hard, tough surface.  

Sources:

Campbell Biology 9th AP Edition

http://www.medicalnewstoday.com/articles/161547.php

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/carbhyd.htm
http://www.mansfield.ohio-state.edu/~sabedon/068dhsyn.gif
http://homebrewsake.com/wp-content/uploads/2010/04/glucose.gif
http://stemlynsblog.org/wp-content/uploads/2012/07/starch.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Taxus_wood.jpg/300px-Taxus_wood.jpg

Taste - A Tongue in Cheek Sense

Picture courtesy of: dft.ba/-2luc

To function as human beings, we all need to eat. Food powers our bodies, allowing for the production of ATP (as previously mentioned on this site) which enables us to perform any and all of our activities, from breathing to dancing and thinking. Taste is essential to consumption. If food were tasteless, there would be little motivation to fuel our bodies. Therefore, we developed a way to enjoy various foods that would fuel our bodies.

On the top of one's tongue there is a collection of organs known as gustatory calyculi or, more commonly, taste buds. The tongue is home to approximately 100,000 individual taste buds. Each of these buds contains about 50-100 cells known as "taste cells" each of which, contrary to popular belief, can perceive a variety of flavors. These cells have a life span of 1-2 weeks before they die and are replaced. There are additional buds on the top, sides, and rear of the mouth, along with the throat. The gustatory calyculi are able to perceive five different types of flavor; bitter, sweet, salty, sour, and savory (often referred to as "umami," a Japanese word that means savory). 

Bitter

Some examples of bitter foods

The perception of bitter taste occurs on a certain receptor in the taste cell known as a G-protein-coupled receptor, specifically the taste receptors, type 2 (TAS2Rs). On these receptors, the substance combines with a substance known as gustducin. Then calcium ions (charged particles) depart from a section of the cell known as the endoplasmic reticulum. These calcium ions create a neurological response in the brain that triggers the "sensory neurons" in charge of perceiving the bitter taste. Interestingly enough, the tongue is more sensitive to bitter flavors than any others. Evolutionarily, this is most likely due to the fact that many toxic foods are quite bitter. Therefore, people more sensitive to this flavor would have been more likely to survive natural selection. Two man made substances, PTC (phenylthiocarbamide) and PROP (6-n-propylthiouracil) taste very bitter to people with specific genetic make ups, but are tastless to people with other genotypes. This is a common test to determine if one is a "supertaster" (more on this later).This ability to taste these chemicals is cause by just two alleles (at TAS2R38 location). 

Some examples of sweet foods, specifically candies

Sweet
Sweet food perception also occurs on G-protein-coupled receptors, specifically T1R2+3 and T1R3. It also involves combining the foodstuff with gustductin. How sweet the substance is perceived as depends on how tightly it binds with the two receptors. 

Salty

Table salt, or NaCl, commonly found in salty foods

The taste receptors for salt, specifically sodium chloride (NaCl) are channels through which sodium ions can flow into the cell. Calcium ions also enter the cell and again trigger a neurological response the causes the perception of the salty flavor. There is one hormone known as aldosterone that regulates the number of salt receptors in the mouth and also the levels of sodium in the body. Other substances that can trigger a similar response include KCl )potassium chloride), NH4+ (ammonium), and cations from the group of alkali earth metals.

Some sour fruits commonly found in nature

Sour

The flavor of sour foods is caused by their acidity. Acidity of a substance is relative to its number of H+ ions, so it is natural that these ions would be the cause of the sour perception. The taste cells perceive sour by expressing the protein PKD2L1. However, the H+ ions themselves can also illicit the taste response, so this gene is not required for this taste perception. 

Some Savory Empanadas

Savory (Umami)

The perception of the umami taste comes from glutamic acid salts (for example, MSG, which is often found in chinese food). This once again occurs on the G-protein-coupled receptors, specifically the glutamate receptors, subsets T1R1 and T1R3. 

Supertasters

One of the most fascinating evolutionary phenomena associated with taste is that of the supertasters. It is believed that this anomaly is caused by an increased amount of taste buds present on the tongue. The first mention of the term "supertaster" was in a study conducted by Linda Bartoshuk. She was conducting a study on taste perception in the 1990s, when her research team noticed that some of the participants had increased response to tastes. As previously mentioned, the ability to taste the chemicals PTC and PROP have been linked with the ability to super taste. It appears that this specific taste receptor comes from one gene (TAS2R38). People who express this genotype prefer sweets as children, do not enjoy alcohol as much as their counterparts, less vegetable consumption, and a lessened tendency to smoke. It is estimated that 25% of people are are supertasters, 50% are regular tasters, and another 25% have a decreased number of taste buds. 

If you don't have access to PROP or PTC, here's a quick and easy test to see if you are a supertaster:

Step 1:

Using blue food color or a blue lollipop, stain your tongue blue. 

Step 2:

Place a piece of hole punched paper on your tongue, making sure that the hole is on top of the blue stained area.

The tongue of a supertaster

Step 3:

Look in the mirror. Using a magnifying glass, count the number of papillae you see. (Unlike the rest of your tongue, the papillae will be unstained). 

If there are more than 35, you are likely a supertaster. If there are 15-35, you are a medium taster, If there are less than 15, you are a non-taster.

Fun Facts:

-Women are more likely to be supertasters than men

-Asians, Africans, and South Americans are also more likely to be supertasters

-The bass player for the band Muckaferguson is a supertaster. They Might Be Giants wrote a song about him (John Lee Supertaster)

-Supertasters like salty foods

-Supertasters are less likely to enjoy fatty and sugary foods

-Supertasters are generally more skinny than regular tasters because they do not enjoy many unhealthy foods, however, they have elevated risk of colon cancer because they do not enjoy bitter vegetables

Still unsure if you're a supertaster or regular taster? Try this test, provided by the BBC. 

Sources:

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taste.html

http://faculty.washington.edu/chudler/tasty.html

http://en.wikipedia.org/wiki/Taste

http://en.wikipedia.org/wiki/Supertaster#Identifying_a_supertaster

http://www.todayifoundout.com/index.php/2010/06/how-to-tell-if-you-are-a-supertaster/

http://www.npr.org/templates/story/story.php?storyId=127914467

http://www.bbc.co.uk/science/humanbody/body/articles/senses/supertaster.shtml

Images:
http://hecooksshecooks.net/wp-content/uploads/2009/05/bitter-foods.jpg
http://www.virginmedia.com/images/ysp%20food%206%20sweets%20on%20la%20rambla,%20barcelona%20by%20helen%20sandell.jpg
http://whatscookingamerica.net/Information/Salt1.jpg
http://www.petitekitchenesse.com/wp-content/uploads/2010/10/fruit.jpg
http://joepastry.site.aplus.net/pics/empanadas1.jpg
http://blogsoop.com/blog/wp-content/uploads/2007/07/supertasters_supertaster.jpg

That's Some Hungry Fungi! Fungus Capable of Eating Plastic Found.

Pestalotiopsis Microspore

Originally created in the 1900s, synthetic plastics have myriad uses. Plastic makes up disposable water bottles, bags, packaging, headphones, cellphones, and countless other everyday items. However, plastics are also detrimental to the environment. Incredibly durable and taking hundreds or even thousands of years to degrade, we waste alarmingly large amounts of the substance every year. The plastics that we throw out can sit in landfills for generations, seemingly impossible to get rid of. However, researchers at Yale have found a fungus from the Amazon rainforest with a rather fantastic property - it is capable of digesting polyurethane.

Known as Pestalotiopsis microspore (member of the family Amphisphaeriaceae, order Xylariales, class Sordariomycetes, subclass Xylariomycetidae, and phylum Ascomycota), the fugus was first found in Ecuador. It is able to subside solely on polyurethane and is the first fungus ever discovered that is capable of doing so. Not only is this remarkable in and of itself, but the fungus can also break down the plastic anaerobically (without oxygen). The team of scientists also found the enzyme that enables the fungus to digest the polyurethane. The researchers believe that this enzyme is a promising development in bioremediation and a huge leap forward in removing plastics from landfills.

Formation Reaction of Polyurethane 

Sources:

http://www.pcworld.com/article/249216/yale_discovers_a_fungus_that_eats_plastic.html

http://www.popsci.com/science/article/2012-02/rainforest-fungus-eats-plastic-potentially-solving-landfill-problems

http://en.wikipedia.org/wiki/Plastic#Environmental_issues

http://en.wikipedia.org/wiki/Pestalotiopsis_microspora

Images courtesy of:

http://www.jessicastuartmusic.com/wp-content/gallery/pre-jsfew/mushroom-spores.jpg

http://upload.wikimedia.org/wikipedia/commons/c/ca/Polyurethane.png

Study Reveals Ability of Yeast to Quickly Evolve

An article on today's New York Times chronicled a fascinating study at the University of Minnesota, a study that may change the way we study evolution. In the study, students discovered that yeast cells used to brew beer can form basic bodies in approximately two weeks.

Researchers created an experiment in which brewer's yeast was fed sugar and encouraged to reproduce, in hopes that the typically unicellular organism would perhaps create some kind of multicellular creature. To encourage this evolution the scientists raised so called "lines of yeast" from a single cell in 10 individual flasks full of "broth" - a soupy substance of nutrients. The flasks were shaken constantly for twenty four hours, and then allowed to settle. One drop of settled cells were put into a new flask and the yeast grew again. This meant that if the yeast fell quickly it would have a larger chance of survival. In a few weeks Dr. Ratcliff, the leader of the study, found that the yeast cells fell rapidly and created a small cloud of yeast at the base of the container. When examined under a microscope, it appeared that the yeast was, in fact, growing in small colonies. Each of these contained hundreds of individual cells. These colonies appeared to be in the shape of snowflakes, and appeared after a mere 60 generations of cells.

One cell of yeast would grow to full size in a matter of hours. Then it's "branches" that grew outwards would cut into each other until they broke. The broken branches would then each sprout another yeast section, which would again snap. This phenomenon is not unique to yeast. A group of unicellular organisms, choanoflagellates, often grow in the same way.

The researches plan to continue their work by looking into the genomes of the new yeast organisms, attempting to find the mutation that allowed for this growth. The yeast themselves are still evolving, changing so that they may reproduce faster and grow more.

source:
http://www.nytimes.com/2012/01/17/science/yeast-reveals-how-fast-a-cell-can-form-a-body.html
http://www.scientificamerican.com/article.cfm?id=test-tube-yeast-evolve

Image courtesy of:
http://dft.ba/-yeast

The Science of Attraction (aka, How We Fall in Love)

Love. It is a powerful human emotion, the driving force behind many of our decision, and (according to Albus Dumbledore) the one thing that Voldemort cannot understand. However, many people do not understand how this phenomenon occurs. Love is, in fact, driving by different chemical and hormonal changes in the brain.

A diagram showing the affects of various neurochemicals on the behavior of the brain as one falls in love.

Love is generally broken up into three stages: lust, attraction, and attachment.

1. Lust

Lust is the initial attraction between two people, based solely on hormones, specifically estrogen and testosterone. Testosterone can be present in both men and women and is a large factor in the sex drive, hence this is the section of attraction that (evolutionarily) primarily concerned procreation. This section tends to last for a few weeks to a few months, depending on the person in question.

2. Attraction
Attraction is the phase generally considered to be "love." This phase causes one to focus more on their significant other and on romance. Throughout this period the brain releases a variety of chemicals which affect one's mood, commonly called monoamines. These include, but are not limited to, the following: pheromones, serotonine, dopamine, and norepinephrine. There is also a sudden spike in the presence of NGH (Nerve Growth Hormone) which eventually returns to the typical level. Scientists believe that these chemicals affect the brain in a way similar to amphetamines. The area of the brain involved with pleasure is stimulated, and the affected party often experiences increased heart rate, insomnia, decreased appetite, and feelings of excitement. They are often totally absorbed with thoughts of their significant other. This stage is believed to last from one and a half to three years.

3. Attachement
Unlike the other two stages, which are temporary, attachement is the phase of love concerned with love term and marital relationships. Attachement increases and strengthens the bonds between people, allowing for connections that can last years or even decades. Attachement is typically caused by shared traits - children, houses, and common interests, to name a few. Attachement is usually associated with an increase in the presence of oxytocin and vasopressin. This stage will last for the remainder of the relationship.

Explanation of various neurochemicals:

Estrogen
Estrogen is a group of chemically similar compounds including estrone, estradoil, and estriol. The two main sex hormones, estrogen and testosterone, are found in both men and women, however, estrogen is more prevalent in women. It allows for the menstrual cycle to occur and allows for women to bear children. Estrogen can help women retain fluid and even reduce the risk of breast cancer.

Testosterone
Testosterone is the primary sex hormone in men, although it is also present in small amounts in women. (The hormone is approximately ten times more present in men than in women.) Testosterone allows for the development of the testis and prostate. Furthermore it increases muscle mass, bone mass, and growth of hair on the body.

Pheromones
Pheromones are various chemicals that both humans and animals excrete in response to various social situations. They are excreted when the being in question is aggregated or alarmed. Some are used as a way of attracting partners of another gender, as neurotransmitter signals, as a developmental trigger, as markings of territory, to transfer information about an animal's history, and to mark a trail for other members of the species. They are also help activate the sex drive in humans and animals.

Serotonine
Serotonine is also a neurotransmitter. It affects moods and mental functions, movement abilities, the ability of the body to regulate temperature and blood pressure, the ability to vomit, the ability to sleep, and the lessening of depression. Certain foods can affect the amount of serotonine in the body, and therefore have an impact on one's ability to sleep.

Dopamine
Dopamine is yet another neurotransmitter. It has similar affects on the body as adrenaline, impacting motor skills, feelings, and ability to feel enjoyment or pain.

Norepinephrine
Norepinephrine is a hormone and a neurotransmitter. When it acts as a hormone is activates the phenomenon commonly referred to as "fight or flight" which helps the body deal with times of disaster. When it acts as a neurotransmitter it helps send nerve signals between neurons.

Oxytocin
Oxytocin, a neuromodulator, plays a big part for women in human reproduction. It allows them to give birth and breastfeed their children. It also has an effect in relationships, enabling recognition, bonding between two individuals, and increases feelings of motherhood and anxiety. People who are lacking in oxytocin may be sociopaths, psychotic, self-obsessed, and manipulative.

Vasopressin
Although vasopressin's main function is in homeostasis (see blog post on sharks), it also facilitates social interaction and bonding.

Check out a cute song about the science of love here.

Sources:
http://www.bbc.co.uk/science/hottopics/love/
http://en.wikipedia.org/wiki/Biological_basis_of_love
http://www.scientificamerican.com/article.cfm?id=your-brain-in-love-graphsci
http://en.wikipedia.org/wiki/Love#Biological_basis
http://www.wisegeek.com/what-is-estrogen.htm
http://en.wikipedia.org/wiki/Testosterone
http://en.wikipedia.org/wiki/Pheromone
http://www.whatisserotonin.com/what-is-serotonin/what-is-serotonin/
http://bipolar.about.com/od/glossary/g/gl_norepinephri.htm
http://en.wikipedia.org/wiki/Oxytocin
http://en.wikipedia.org/wiki/Vasopressin

Scishow!

Here are some fantastic videos from Hank Green's new SciShow channel.