Fructose

FRUCTOSE

Fructose is a monosaccharide, in dry form it is a very sweet, white, odorless, crystalline solid. Fructose also has the distinction of being the most water soluble of the sugars. It is absorbed directly into the bloodstream during digestion and is often times referred to as fruit sugar because of its high concentration in fruits, but it is also found in some vegetables and honey.

Fructolysis or fructose catabolism is analogous to glycolysis, the catabolism of glucose.

If you consume high fructose foods the result is a lower circulating level of insulin and leptin. Since both insulin and leptin decrease appetite it is suspected that high fructose consumption increases weight gain.

 

http://katabatic.tv/work/snl-corn-syrup/

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.

Analysis of Carbohydrates (Sugars)

Objective:

The purpose of this experiment was to use a spectroscopic method to determine the concentration of carbohydrate solutions. The methods used included a measurement of the carbohydrate’s intrinsic UV absorbance. This experiment allowed for the opportunity to experiment with the various assays available to determine carbohydrate concentration.

Methods:

 The first step was to calculate the standards I would be using. I started this by obtaining seven micro-centrifuge tubes, four of which were for the standard and three of which were the disaccharide samples. I labeled the standards blank, 0.5, 1, and 2, and the samples Fructose, Sucrose, and Lactose. For the standards tubes, I added the following volumes of glucose enzyme reagent, the appropriate standard, and water:

	Reagent	Standard	H20
0.5	1000 ml	20 ml	50 ml
1	1000 ml	20 ml	50 ml
2	1000 ml	20 ml	50 ml
Blank	1000 ml	0 ml	70 ml

For the samples, I added the following volumes of enzyme reagent, the appropriate sample, and their respective enzyme:

	Reagent	Sample	Enzyme
Fructose	1000 ml	20 ml	50 ml
Sucrose	1000 ml	20 ml	50 ml
Lactose	1000 ml	20 ml	50 ml

I started doing the standards first, and then started the sugar samples. I added the volumes into the tubes from smallest volumes to the greatest, making sure to replace the pipette tips when switching between the different solutions. I then capped all of the tubes and put them into the incubator at 37C for 15 minutes.
After the incubation period, I took all of the tubes out of the incubator and transferred the content of each tube to a 1 mL cuvette. I then set up the absorbance meter to read at 500 nm for each of the standards and the samples. I took the blank sample and put it into the absorbance meter to zero the meter out. Afterwards, we put the rest of the  standard and samples into the absorbance meter one at a time and recorded their absorbances. I had to do a double dilution for the sucrose by transferring the solution back into a micro-centrifuge tube from the cuvette and then putting 500 ml of the solution and 500 ml of water into a different cuvette and taking the absorbance again.

Data and Calculations: 

Calculations of Standards

Figure 1: A standard curve plotting the absorbance at 500 nm vs. the carbohydrate concentration in each of our standard.

The known concentrations of Sucrose:

My concentrations of Sucrose:

The known concentrations of Lactose:

My concentrations of Lactose:

Results: 

Overall results for this lab seemed to be acceptable. I had to do a double dilution for the lactose because my first absorbance value for lactose was 1.384, which was outside of my absorbance range. After the double dilution my lactose absorbance went down to 0.640 making both my sucrose and lactose in the range of my standards. The fructose was not within standards due to unknown lab error and I will repeat this process at a later time.