ChemFAQs: October 2012

Tuesday, October 30, 2012

Galactose, and Fructose, and Glucose...Oh My!

Courtesy of partycheap.com

Happy Halloween everyone! Given the holiday, this week’s topic will be the chemistry of candy. (We all love our candy!) From Snickers and M&M’s to caramel and Skittles; one of the key ingredients present in all of these is sugar. We know we love it, but what does this magical little molecule look like?

Courtesy of envirodad.com

Sugar is actually a general term used to refer to vast class sweet-flavored compounds utilized in food. Chemically, sugars are a member of the carbohydrate family. This means that they consist only of carbon, hydrogen, and oxygen, typically with a 1:1 ratio of carbon to H₂O (C_n(H₂O)_nhence the term carbohydrate). Different types of sugars can be extracted from various sources. The most familiar type of sugar (table sugar) is sucrose, a compound formed from the two simple sugars glucose and fructose.

Sugars are classified as monosaccharides (“simple sugars”) which are made up of a single carbohydrate unit, disaccharides that are made up of two carbohydrate units, or oligosaccharides that are composed of many carbohydrate units. The most common monosaccharide is glucose, a molecule used as the primary energy source for cells in our body! Fructose and galactose are two other common monosaccharides. In addition to sucrose, other common disaccharides are maltose (made of two glucose molecules), which originates from grains, and lactose (made from galactose and glucose), which is found in milk.

Although small, the differences in these disaccharides can lead to big biological effects. In order for the body to use the sugar in the foods you consume, it first must be break down disaccharides into its simple sugar units such as glucose. If you or someone you know is lactose intolerant, that means that you/they lack an enzyme in their body known as lactase, which is responsible for breaking lactose into galactose and glucose. This phenomenon also explains why humans lack the ability to survive on grass like other animals. Humans lack enzymes known as cellulases that break down the special type of bond formed between glucose molecules in cellulose, known as a β-linkages. We are unable to get energy from cellulose because we cannot break it down into glucose units. Unfortunately, plants are roughly 33% cellulose by weight, meaning that most of the usable energy in plants goes to waste!

So this Halloween, after you’ve collected all of your goodies, take a look at the ingredients and see what sugars are in your candy! Hey, I did say that glucose was a primary energy source, so eat up!

Candy Links:

Sources:

Saturday, October 27, 2012

Chemistry: One Big Family

Among the sciences, chemistry is uniquely situated at the crossroads between physics and the more applied sciences such as biology. Because of this relationship, chemistry is sometimes referred to as "the central science." Simply put, chemistry is concerned with understanding the interactions between atom (chemical reactions), structure, and composition of matter (or “stuff” in non-technical terms). Given chemistry’s central role, chemists work on a wide variety of projects. In a broad sense, chemistry can be divided into 4 subdisciplines: biological, inorganic, organic, and physical.

Biological

An enzyme with molecules bound

As you might guess, biologitcal chemistry (or biochemistry) is concerned with the chemistry of life. Biochemists, such as this year’s Nobel Prize winners in chemistry, study the structure of large biomolecules like DNA, proteins, sugars, and fats. Progress in this field has lead to the development and utilization of modern medical science.

Inorganic

Inorganic chemists play a vital
role in aluminum recycling.

Inorganic chemistry is broadly defined as the chemistry of metals. Inorganic chemists study the structure and physical properties of metallic compounds and apply that knowledge to fields ranging from semiconductors (the “guts” of all modern electronics) to industrial scale catalysts that make chemical reactions faster and more efficient.

Organic

Structure of Linezolid: A man-made antibiotic

Organic chemistry revolves around the chemistry of carbon (not related to “organic” food!). Organic chemists specialize in creating complex molecules from smaller, simpler precursors. Everything from plastic cups to cardboard to our own bodies is made of carbon, and so organic chemists have their hands in quite a few cookie jars.

Physical

MRI machines use techniques
developed by physical chemists to
take images of our bodies.

No, this is not the kind of chemistry that you want to have with the cute girl who sits behind you in fifth period English. Physical chemistry is the interface between chemistry and physics. Physical chemists are concerned with applying and studying chemistry at the atomic and subatomic level. In the course of their work, they use advanced equipment such as super computers, high-powered magnets, and lasers (pew! pew!).

In reality, most work in chemistry can't be separated into just one of these categories, and so the majority of projects involve a great deal of collaboration between chemists with differing specialties.

Image sources:
http://www.rcsb.org/pdb/explore/explore.do?structureId=1PFK
http://academyoffood.blogspot.com/2012/09/you-can-tell-coke-from-pepsi-but-can.html
http://en.wikipedia.org/wiki/Linezolid
http://www.diagnosisms.com/2012/04/30/mri-for-multiple-sclerosis/

Thursday, October 25, 2012

Molecule of the Week: Cinnamaldehyde

What’s the first thing that comes to mind when you think of Hot Tamales or Fireballs…most likely its cinnamon! From jelly beans to spiced breads, cinnamon is found in a wide range of today’s foods. Behind this distinctive smell and taste is cinnamaldehyde a common organic compound. As a pure compound, cinnamaldehyde is a viscous pale yellow liquid which is naturally found in the bark of cinnamon trees¹.

Cinnamaldehyde is also associated with several health benefits. In addition to imparting its unique flavor, it is used as a fungicide, an antimicrobial agent, and as an anticancer agent (albeit in levels unachievable through dietary intake). These health benefits help explain why cinnamon is a commonly used in Chinese herbal medicine². Due to cinnamon’s powerful properties, the popular gum Big Red, in addition to having its powerful cinnamon flavor also effectively prevents oral bacterial growth by greater than 50%¹. Looks like we should all be adding more cinnamon to our diets!

References:

Sunday, October 21, 2012

The Science of Smell

Sniff, sniff! What’s that smell? Whether it’s a home-cooked meal or a pair of dirty sneakers, the power of smell is an amazing thing. But how does smell work chemically? In a recurring section of this blog, we’ll soon be featuring a molecule of the week, many of which are associated with a particular smell, but how does the structure and shape of a particular molecule translate into all the wonderful (and not so wonderful) smells that surround us.

The human sense of smell (olfactory sense) is capable of distinguishing over 10,000 different odor molecules¹! Our keen sense of smell is enabled by over 900 different genes within our DNA, approximately 40% of which code for different olfactory receptors. Hopefully you read Spencer’s post last week (if not scroll down), because these receptors are actually members of the Class A Rhodopsin-like family of G protein-coupled receptors (GPCRs).

All around you are thousands of molecules in their gaseous form buzzing through the air. These easily evaporating, or volatile compounds, readily go into the gas phase and are inhaled as you breathe in. As these molecules pass through your nose, they come pass over a small postage stamp sized area in your nose that contains millions of olfactory receptor neurons, an area known as the olfactory epithelium. Each of these neurons has miniscule projections, called cilia, which reach out into the air. These cilia are the olfactory receptors, which are proteins specifically designed to bind to the volatile compounds that are found in the air. Each receptor has the ability to bind a range of odor molecules but with varying strengths². Once bound, the protein undergoes a structural change, binding and activating an olfactory-type G protein within the cell. This then triggers the conversion of adenosine triphosphate (ATP) into cyclic adenosine monophosphate (cAMP) causing the opening of ion channels in the cell wall. As Ca²⁺ and K⁺ enter into the cell, an electrical signal is created which shoots down the neuron and is subsequently received and translated in the brain into a smell³.

Depending on what combinations of molecules bind to the array of receptors in your nose, you smell a different odor! Due to the hundreds of receptors and their varying affinities for different molecules, we have the ability to distinguish thousands of combinations of molecules from the smell of freshly cut grass, to fruits, to freshly baked cookies!

References:

Tuesday, October 16, 2012

2012 Nobel Prize in Chemistry (Translated)

Drumroll please…And the 2012 Nobel Prize in Chemistry goes to…Robert J. Lefkowitz and Brian K. Kobilka “for studies of G-protein-coupled receptors.”¹ So, why is this work so important? Well G-protein-coupled receptors (GPCRs) are the primary means by which all cells in our bodies communicate with each other. So for example, imagine that you are allergic to pollen, and you happen to breathe some in. Immune cells in your nose recognize the pollen as foreign and decide to take the “shoot first and ask questions later” policy by sounding the alarm. This “alarm” consists of a small molecule called histamine. The histamine in your system is detected by nearby cells that have histamine receptors.

These receptors fall into the large family of receptors called…Yep, you guessed it, G-protein-coupled receptors! A typical GPCR is a protein consisting of 7 helixes embedded in the cell membrane with part of the receptor sticking out of both the inside and the outside of the cell.² When histamine is detected by the GPCR outside the cell, it enters the space in the middle of the GPCR. This causes a change in the three-dimensional shape of the receptor inside the cell. The new, more open shape allows the GPCR to react with the inactive form of a G-protein called G-abg (G-alpha, beta, gamma). This reaction causes the inactive G-protein (or Guanine nucleotide-binding protein if you speak chemicalese) to break apart into smaller G-proteins called G-alpha and G-beta,gamma.³ The G-alpha piece goes on to start a chemical chain reaction in the cell that ultimately leads to your allergy symptoms. As long as the histamine is bound to the GPCR, it will continue to make more and more G-alpha (intensifying your allergy symptoms). Eventually, the histamine will be released back into your system where it can move to the next cell and continue making your day miserable. In this way, a relatively small number of histamine molecules can have a broad impact on your body.

Fortunately, bright scientists like Drs. Lefkowitz and Kobilka have figured out the structure and function of GPCRs. Armed with this knowledge, we can create molecules that bind to these receptors and prevent the bad effects that molecules such as histamine have on our bodies. Like an NBA team playing a high school team, “antihistamines” box-out the histamine by occupying the paint a.k.a. the place where histamine normally would bind to the histamine receptor. In fact, most medicines work by acting on various GPCRs throughout your body.² In essence, this research on GPCRs has fundamentally changed and expanded our understanding of how drugs work. Ultimately, this will lead to more effective treatment of diseases!

References:

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2012/

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2012/popular-chemistryprize2012.pdf

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

Nobel TIME!

Courtesy of Wikipedia.org

Well folks, it’s that time of year again. No, not fall or time to hastily piece together a Halloween costume. It’s Nobel Prize season! You may be thinking, “What is the Nobel Prize? Why is it important?” Essentially, the Nobel Prize is one of the highest honors that someone can earn in his/her lifetime (you can’t win a Noble Prize if you are dead). The prize is named after chemist and inventor Alfred Nobel. Near the end of his life, Nobel was shamed by the fact that many of his inventions, including dynamite, ushered in a new era of military destruction on a massive scale.¹ He decided that he would dedicate his vast fortune to the establishment of a prize for individuals whose work has benefitted all of mankind. Nobel Prizes are awarded every year in the fields of chemistry, physics, medicine/physiology, literature, economics, and peace. For more information, you can visit the website for the Nobel Prize www.nobelprize.org.