S-STEM Scholar McKenna Manning's Blog
Thursday, December 5, 2013
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/
Wednesday, November 27, 2013
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!
Thursday, November 21, 2013
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!
Thursday, November 14, 2013
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!)
Thursday, November 7, 2013
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.
Thursday, October 31, 2013
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.
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.
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