POLYSACCHARIDES

POLYSACCHARIDES- STRUCTURE AND PROTECTION

Greetings, fellow bloggers. Let’s take a look at the inner workings of the Carbohydrates iceberg. We’ll be looking at some not so sweet saccharides known as glycans.

Polysaacharides or glycans are extremely long chains of monomer units connected via O-glycosidic linkage and have molecular weights between medium to high.

Polysaccharides can either be nomo- or hetero. Homopolysaccharides consist of the same monomer units, while heteropolysaccharides have two or more varying monomer units. “Kinda self explanatory is it?” These glycans also have branching which can be seen in starch (amylopectin) and glycogen.

Amylopectin


Amylopectin is a type of starch produced by plants with monomeric units of glucose.This complex carbohydrate is an used as energy storage molecule in plants. It can be found in the leaves, stems, roots and fruits for example. Furthermore it is a good dietary supplement for us humans, it can be found in such foods as wheat, potatoes, rice and cassava. (By the way I love cassava, fried, boiled, baked, I love it!!!!!)
What makes it such a good storage molecule??????
Well in this case glucose is highly water-soluble and it takes up a lot of space but starch is insoluble in water and compacts glucose monomers in a space efficient way. Don’t worry glucose molecules can be retrieved with easy when body needs energy.

Glycogen

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Like amylopectin glycogen consists of monosaccharide units of glucose. Unlike amylopectin glycogen is found in humans, mostly in the liver cells and muscles. When we eat cassava or starchy products or even sweet stuff, the excess glucose lying around in our bodies is converted to glycogen and stored in our liver and muscles. So when we need energy, signals are sent and glycogen is broken down into glucose molecules.
What’s so special about Amylopectin and Glycogen????????

Linkage and branching

Both amylopectin and glycogen have alpha 1-4 glycosisdic linkage and 1,6 branching. Both are storage molecules and have similar structure.

Difference?

Their branching is different, glycogen is more highly branched than amylopectin with 8-12 glucose residues, while amylopectin has between 24 to 30 glucose residues in length.

For all the Shrimp lovers out there…………………..

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I’m sure your wondering what is the connection between shrimp and carbohydrates, well we know there is clear link between shrimp and cholesterol, but we won’t go there.Image
Shrimps and seafood in general are part of a class known as Arthropods; the largest phylum of organisms in the world. Yes, arthropods range from spiders to crickets to cockroaches and seafood(TASTY!!). This phylum is successfull for many reasons, they possess chitin. Chitin is homopolysaacharide that carries out a protective role when it comes to shrimp, lobsters and crabs and many other arthropods. It is found in their exoskeleton and has beta 1-4 linkage of amino N-acetyl-glucosamine.

Peptidoglycan

ImagePeptidoglycan is a layer found in Gram-postive and Gram negative bacteria. It is more abundant in Gram positive bacteria. It is a heteropolysaccharide with covalently linked sugar based monomeric units that are crosslinked by short peptide chains. This glycan is a structural component in bacteria and is constantly broken down, recycled and renewed to fit the shape of the bacterial cell.Image

Lets’s take a Test and see if You pass

The presence of peptidoglycan can be confirmed by Gram staining. Gram staining was devised by a Danish bacteriologist, Hans Christian Gram in 1882. This technique differentiates groups of bacteria into Gram negative and Gram positive.

The materials needed to test these bacteria include:
-Crystal-violet dye
-Gram’s Iodine solution
-Acetone (decolourizer)
-Safranin (counterstain)

Crystal-violet dye and Gram’s iodine solution are both added to desired cultured bacteria, which are present on slides. These reagents form a crystal violet iodine complex.

The sample slide is rinsed with acetone to decolourize the sample. Acetone dehydrates and shrinks the peptidoglycan layer. Since the complex is still present in the layer, it is trapped by the shrinking and tightening from dehydration.

Safranin counterstains the sample with a red stain. Once the sample has been carefully rinsed, the colour observed under a light microscope determines whether the bacteria is Gram Positive or Gram Negative.

If purple and pink colouration is seen among the bacterial cells, congratulations they pass the test, it is Gram positive.

PASS PASS PASS PASS PASS PASS PASS PASS

However if a red colouration is observed, then the bacteria is Gram negative.

FAIL FAIL FAIL FAIL FAIL FAIL FAILImage

How is it that Gram positive bacteria retains the crystal violet dye and Gram negative bacteria does not????????

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Its all in the layers, Gram positive bacteria have thick layers about 80nm, while Gram negative bacteria contains less than 10nm. The thin layer in Gram negative bacteria is unable to retain the crystal violet dye and iodine complex after decolouriztaion dye.

Now, Guys I hope you learnt something!!! Like for instance when I was doing peptidoglycan layer, it brought me back to BIOL 1262, “sigh” GOOD TIMES!
So we have fully scaled the carbohydrates iceberg, well to an extent, from the sugar top to the not so sugary center. Please look out for more posts from yours truly,

                                                                                                    Biochemaddict21

 

References
Bruckner, Monica Z.2012. “Gram Staining”. Microbial Life Educational Resources. Last Updated May 29th, 2012. Date Accessed April 12th 2013.serc.carleton.edu › … › Research Methods › Basic Cell Staining

Gaspirtz. “Dysfunctional Bacteria Relationship”.Date Accessed April 12th.http://www.gaspirtz.com/07-bacteria.shtml

Hudson, Dawn.2002-2013. “Cliphart Illustration of Cartoon Bacteria”.Date Accessed April 12th, 2013. http://www.acclaimimages.com/_gallery/_image_pages/0110-0903-1009-0232.html

Quinto, Karen.” SCIENCE.ART.NERDINESS. COMBINED.” Cartoons.Date Acessed 12th April 2013.http://karenquinto.com/cartoons/


Nelson, David L. , and Michael M. Cox. 2008. Lehninger Principles of Biochemistry. 5th Edition. Madison Ave. New York, NY: W.H. Freeman and Company

Ophadt, Charles E. 2003. “Glycogen”. Virtual Chembook.Date Accessed April 12th, 2013.http://www.elmhurst.edu/~chm/vchembook/547glycogen.html

Wisegeek. 2003-2012. “What is Amylopectin?”Date Accessed April 12th, 2013.http://www.wisegeek.com/what-is-amylopectin.htm

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