~~CARBOHYDRATES~~

CARBOHYDRATES PODCAST REVIEW

(PART I)

So this week, we started looking at a very popular group of  bio-molecules —> CARBOHYDRATES

I have looked at my lecturer’s  YOUTUBE PODCASTS on CARBOHYDRATES. The topics-  basic composition,functions,isomerism,hemiacetal & hemiketal formations and sugar derivatives, were effectively delivered. It was quite simple to follow along  and understand  as he explained. The pod-casts are user friendly and student friendly, in that, anyone (normal person out there or student) can learn at their own pace, as he rightfully said.

~~The following are what I have grasped from podcast 1~~

>>BASICS<<

>> Most abundant bio-molecule

>>Atomic composition: carbonoxygenhydrogen

>> General formula:  (CH2O)n

>> BIOLOGICAL SIGNIFICANCE:

  • excellent Energy source

  • storage {GLUSOSE –>glycogen (animals/humans), starch (plants)}

  • structural formation {cellulose, chitin, parts of nucleic acids}

  • precursor molecule

>> are Sugars or saccharides

>> can exist as

  • monosaccharides

  • large polymers (disaccharides, trisaccharides etc.) 

  • polysaccharides

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>>MONOSACCHARIDES<<

~Simplest sugars

~can have different number of carbon atoms: (CH2O)n

~can exist as ALDOSES or KETOSES

~all are REDUCING SUGARS

~sweet

~readily soluble in water

Egs. glucose,fructose, ribose, glyceraldehyde, dihydroxyacetone

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>>CHIRAL CARBON<<{Asymmetric carbon}

  • Carbon atom having FOUR (4) different substituent groups attached

Eg. glucose has 4 chiral centres

 carbons 2-5 are chiral

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>>ENANTIOMERS<<

  • Pairs of structures that cannot be superimposed by rotation 

  • structures are designated D (right) and L (left), which is determined by the position of the OH-group of the chiral centre

Eg. glyceraldehyde

D- SUGARS are mirror images of their L-SUGARS

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>>EPIMERS<<

  • Carbohydrates that differ in configuration at one end of the assymetric carbon

Eg. galactose is an epimer of glucose at the C4 position

       mannose is an epimer of glucose at the C2 position

EPIMERS OF GLUCOSE

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>>ANOMERIC CARBONS<<

An anomeric carbon is one on which the carbonyl group is attached

The ring structures are possible because of the an alcohol and a carbonyl carbon reacting which can reversibly form a covalent bond. 

~~If the carbonyl is an aldehyde, the product is a hemiacetal otherwise if the
carbonyl is a ketone, the product is a hemiketal.~~ 

The OH-group on C1  of a cyclic structure can project below the ring (α anomer) or above the ring (β anomer)

GLUCOSE

a-D-Glucopyranose                                   b-D-Glucopyranose

Hayworth projections~ reprsentations of cyclic sugars

Fischer structures~ open chain structures

##aldehyde or ketone reacts with a distal OH-group to form a CYCLIZED  structure##

{well explained in podcast}

—-And that is basically what I learnt ….Hope you learnt something too and any questions can be cleared up by actually looking at the pod-casts. Until then, have fun learning!!!! —-

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CARBOHYDRATES

(PART II)

Again, the material covered in this pod-cast- glycosidic bonding, disaccharides, polysaccharides and glucose oxidase system– were adequately conveyed.

We did a really FUN, COLOURFUL lab!!!! FOOD TESTS!!!!! 

Molisch Test

ALDOSE……………………………………. KETOSE
Seliwanoff’s Test

Benedict’s Test

Modified Barfoed’s Test

Bial’s Test

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HIGH FRUCTOSE CORN SYRUP!!!

        

According to Dana Flavin (MS, MD, PHD)

“Americans are being poisoned by a common additive present in a wide array of processed foods like soft drinks and salad dressings, commercially made cakes and cookies, and breakfast cereals and brand-name breads.

This commonplace additive silently increases our risk of obesity, diabetes, hypertension, and atherosclerosis.”

It is being called a “benigned food additive”  and “toxic additive”

High Fructose Corn Syrup (HFCS) is used in almost everything, from bread, cereal, soda, juices, and many other food items.

~What exactly is it?~

High-fructose corn syrup (HFCS)—also called glucose/fructose in Canada,glucose–fructose syrup (GFS) in the EU, and high-fructose maize syrup in other countries—comprises any of a group of corn syrups that has undergone enzymatic processing to convert some of its glucose into fructose to produce a desired sweetness.

A sweetener made by processing corn syrup to increase the level of fructose,usually to between 42% and 55% of the total sugar, with the balance being glucose. It is used extensively as a sweetener in processed foods and softdrinks, particularly soda and baked goods, but it is included also in many foods not normally thought of as sweet foods.

~Why is high fructose corn syrup bad for you?~

Since HFCS was introduced into the food industry almost 30 years ago, obesity rates have skyrocketed.  Many believe that HFCS is part of the reason of the obesity epidemic in America.  Not only is it bad for your health, consuming too much of the corn syrup can lead to diabetes.

“High dietary intake of fructose is problematic because fructose is metabolized differently from glucose. Like fructose, glucose is a simple sugar. Derived from the breakdown of carbohydrates, glucose is a primary source of ready energy. Sucrose (table sugar) comprises one molecule of glucose and one molecule of fructose. Thus, excessive sucrose intake also contributes to the rise in overall daily fructose consumption. Glucose can be metabolized and converted to ATP, which is readily “burned” for energy by the cells’ mitochondria. Alternatively, glucose can be stored in the liver as a carbohydrate for later conversion to energy. Fructose, on the other hand, is more rapidly metabolized in the liver, flooding metabolic pathways and leading to increased triglyceride synthesis and fat storage in the liver. This can cause a rise in serum triglycerides, promoting an atherogenic lipid profile and elevating cardiovascular risk. Increased fat storage in the liver may lead to an increased incidence in non-alcoholic fatty liver disease, and this is one of several links between HFCS consumption and obesity as well as the metabolic syndrome.

Fructose may have less impact on appetite than glucose, so processed foods rich in fructose can contribute to weight gain, obesity, and its related consequences by failing to manage appetite. Additionally, loading of the liver with large amounts of fructose leads to increased uric acid formation, which may contribute to gout in susceptible individuals.”

REFERENCES:

http://www.lef.org/magazine/mag2008/dec2008_Metabolic-Dangers-of-High-Fructose-Corn-Syrup_01.htm

http://healthfoodandgreed.wordpress.com/2013/01/23/what-exactly-is-high-fructose-corn-syrup/

http://en.wikipedia.org/wiki/High-fructose_corn_syrup

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HOW ABOUT THAT!

The pyranose or the furanose ring structures can be formed by the fructose straight-chain.

If temperature is increased, equilibrium is shifted in the direction of the furanose form, and this causes the solution to become less sweet.

Therefore it can be concluded that high temperatures reduce the sweetness of fructose solution.

HONEY BEES IN DANGER???!!!!!!!!!!!!! 😦

HEAT FORMS POTENTIALLY HARMFUL SUBSTANCE IN HIGH FRUCTOSE CORN SYRUP: Read more about this at any one of the following links provided.

http://www.sciencedaily.com/releases/2009/08/090826110118.htm

http://www.docstoc.com/docs/16572674/Heat-forms-potentially-harmful-substance-in-high–fructose-corn-syrup

http://www.infiniteunknown.net/2009/10/20/study-high-fructose-corn-syrup-and-its-toxicity-to-the-honey-bee/

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 QUIZ TIME!!!! please attempt!!

1. Select the correct multiple answer using One of the keys a,b,c,d or e provided.

 [a]1 only

[b]1,3,4

[c]2,3 and 4

[d]1,2 and 3

[e]answer not given

Polysaccharides which do not  have structural roles include:

[1]galctose,starch, glygogen

[2]cellulose,hemicellulose,chitin

[3]amylose,glycogen, starch

[4]amylopectin, starch, glycogen

2. Sucrose is a

[a]reducing sugar

[b]protein

[c]trisaccharide

[d]non-reducing sugar

[e] none of the above

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