Happy Thanksgiving Everyone!!

I would like to say that I am looking forward to this Thanksgiving Day because I am going to relax and reflect on all of the wonders (of which there truly are many) in my life that I am thankful for. Unfortunately, this Thanksgiving falls much too closely to FINALS, and so I will not be relaxing and my reflecting over the next four days will be centered entirely on calculus, differential equations, JAVA programing and – of course – organic chemistry!!

It is my hope for all of you that you have a brilliant and safe holiday, that you enjoy a marvelous feast with your friends and family, and I also wish you the best on your finals!

More About Fischer Projections

Fischer Projections are drawn with the carbon chain extending out vertically with the most oxidized end of the molecule on the top (assuming there is a most oxidized end).

Using a Fischer Projection it is easy to see if the Projection represents a meso compound. Simply draw a line across the drawing half way down. If there is an even number of carbon atoms the line is drawn across the carbon-carbon bond. If there is an odd number of carbon, the line is drawn across the middle carbon atom and the substituents. Now, just check to see if above the line mirrors below the line. If they mirror they are meso if they do not then they are chiral (and capable of being optically active).

What do these three structures have in common?

EVERYTHING – they all represent the same sugar!

 

What’s in a name? As it turns out in chemistry EVERYTHING

Chemists like things to be clear, and the way they succinctly and unambiguously name molecules serves to clearly describe each one- you just* have to become familiar with the rules of IUPAC nomenclature and the wonder of Fischer Projections.

I spent many hours this week learning basic carbohydrate terminology and practicing my Fischer Projections. Fischer Projection is a convenient way of drawing molecules that have multiple stereocenters and they look something like this:

 

Figure 1: The Fischer projection of the aldose D-glucose and the ketose D-fructose.

(*unfortunately, there are many, many rules and just when you think you know them all they become updated! But, don’t be discouraged only chemists are responsible for the truly complicated larger molecules!)

 

More on HFCS

More investigation reveals:

High fructose corn syrup is an artificially manufactured sweetener that uses an enzymatic process to convert glucose syrup from corn into a fructose/glucose mixture.

Because HFCS are cheaper to produce than sucrose, it is a common additive to foods produced in the United States, it is a VERY common additive to low-fat foods.

Glucose:

-        Important in energy production

-        Critical to the production of proteins and lipids

-        6 membered ring

-        Glucose is the energy of life

In a sample of 120 calories of glucose:

-        96 calories (80%) is used by all the organs in the body because glucose is the energy of life

-        24 calories go to the liver

-        Insulin goes up and the brain registers food is available

-        0.42% of the original 120 calories ends up as fat

-        (½ calorie of VLDL is created)

-         

Fructose:

-        Has no biological role

In a sample of 120 calories of HFCS (60 from fructose, 60 from glucose):

-        60 calories (100%) of the fructose goes to the liver because it is only metabolized in the liver

-        12 calories of the glucose goes to the liver

-        72 total calories hit the liver

-        No insulin change

-        The waste product of fructose metabolism is uric acid which causes gout and hypertension

-        Triglycerides go up

-        30% of the original 120 calories ends up as fat

-        A high HFCS diet IS a high fat diet!

Marshall and Kooi, 1957 R.O. Marshall and E.R. Kooi, Enzymatic conversion of d-glucose to d-fructose,

Science 125 (3249) (1957), pp. 648–649.