The adventures and experiences this semester in Biochemistry!

Posts tagged “Non-reducing sugars

Video

Carbohydrates: Video review

 

Hey guys, as part of my Blog assignment for my course BIOL1362, we had to include a video review on two topics covered. I chose as my first topic Carbohydrates in order to just give a general idea of what is on the web. Besides using my lecturer’s videos, I looked at many videos on YouTube. One channel in particular called The New Boston caught my attention. The title of the video is Biology Lecture – 7 – Carbohydrates. It caught my attention due it’s just above 4 minutes length. I was a bit puzzled compared to the videos I found with lengths of 15 minutes and over, with my lecturer’s being 45 minutes.  In this review I will analyze the video’s content and further re-explore the topic, Carbohydrates.

Primarily, Carbohydrates are called such because it contains essential hydrates of carbon and are composed of water and carbon. Carbohydrates can be given by the equation (CH2O) n.

naming the biomolecule

naming the biomolecule

Carbohydrates have four distinct functions. These are,

1. Used as a storage medium (starch in plants and glycogen in animals)

2. Used as an energy source since it can be broken down easily

3. Used as a Precursor Molecule in the synthesis of certain bio molecules

4. Has a structural function (Cellulose in plants and Chitin in exoskeletons or insects)

These biomolecules are classed as Monosaccharide, Disaccharide, Oligosaccharides and Polysaccharides. Each is structurally different in terms of the amount of simple sugars it contains.

Monosaccharide simple sugars with multiple –OH groups bonded on a number of carbons.

Disaccharide -2 monosaccharide covalently linked.

Oligosaccharides- few monosaccharides linked covalently together.

Polysaccharides – polymers consisting of chains of monosaccharide units.

The bond which is formed between Carbohydrates is called a Glycosidic bond . These biomolecules can be classed into Reducing and Non-reducing sugars. A Reducing sugar is a carbohydrate that serves as a reducing agent due to its free aldehyde or ketone functional groups in its molecular structure. Glucose, fructose, lactose,  and maltose are examples of reducing sugars since these have free aldehyde or ketone functional groups in its molecular structure. A Non-reducing sugar is a carbohydrate that is not easily oxidized by a weak oxidizing agents in basic aqueous solution.  In basic aqueous solution, non-reducing sugars do not generate compounds containing an aldehyde group. One such example is sucrose, which contains neither a hemiacetal group nor a hemiketal group.
In terms of the video, “TheNewBoston” introduces the topic as carbohydrates and makes an important note that we have learnt before- Carbohydrates are biomolecules. He also states that the Human Body “loves” Carbon, which makes up the back bone of a carbohydrate. He implies that the body actively uses molecules made of carbon. Describing carbohydrate structure, he illustrates using a drawing the ratio to which carbohydrates is made up, which is a 1:2:1 ratio, in terms of Carbon, Hydrogen and Oxygen respectively. In the video, “TheNewBoston” only makes a slight suggestion to where we, humans, obtain carbohydrates. He also describes that we use carbohydrates as a source of energy, also giving the example Glucose and how it used in a brief description.

Honestly, I did not find the video having sufficient information for an “Introduction to Carbohydrates” with its just above 4 minutes time. It lacked the proper introduction to Carbohydrate structure and function. As I proceeded to view the channel, I saw there were at least 3 other carbohydrate videos going in-depth about structure, organization and use. Re-thinking, I thought this was logical in order to go in-depth per say in each section. The video is creative and I do recommend that you view the others along with it to truly gain a fair background on the topic.

I do hope this was helpful.

-Carlos

References

“Nonreducing Sugar.” OChemPal. science.uvu.edu/ochem/index.php/alphabetical/m-n/nonreducing-sugar/ (accessed April 1, 2013).

Video
The New Boston,  http://www.youtube.com/watch?v=_WGD5UhqShI

Pictures
http://www.chemistryland.com/ElementarySchool/BuildingBlocks/CarbohydratesCO2water.jpg

 


Reflection 4. Carbohydrates: I knew you were Trouble when you walked in!

So, in my last post I gave the answers to the questions I posted and the link to which you can find some more questions to test your knowledge. This time around I wanted to talk about Carbohydrate structure and Carbohydrate tests.  Many of us get easily confused by tests! I’ve tried simplify it into a flow chart for convenience. Let’s get started!

How are carbohydrates classified?

These biomolecules are classed as Monosaccharide, Disaccharide, Oligosaccharides and Polysaccharides. Each is structurally different in terms of the amount of simple sugars it contains.

Monosaccharide -simple sugars with multiple –OH groups bonded on a number of carbons.

Disaccharide -2 monosaccharide covalently linked.

Oligosaccharide- few monosaccharides linked covalently together.

Polysaccharides – polymers consisting of chains of monosaccharide units.

structure-of-carbohydrates

Carbohydrate Class

The bond which is formed between Carbohydrates is called a Glycosidic bond . Note its position on the diagram.  In Carbohydrates part 1 we mentioned the importance of Carbohydrates and structure.  When carbohydrates bond, its functions change.

Diagram with Glycosidic Bond

Diagram with Glycosidic Bond

What are tests for Reducing sugar and Non-reducing sugars?

A Reducing sugar is a carbohydrate that serves as a reducing agent due to its free aldehyde or ketone functional groups in its molecular structure. Glucose, fructose, lactose,  and maltose are examples of reducing sugars since these have free aldehyde or ketone functional groups in its molecular structure.

A Non-reducing sugar is a carbohydrate that is not easily oxidized by a weak oxidizing agents in basic aqueous solution.  In basic aqueous solution, non-reducing sugars do not generate compounds containing an aldehyde group. One such example is sucrose, which contains neither a hemiacetal group nor a hemiketal group.

Primarily, one can use a series of tests to differentiate carbohydrates. Benedict’s reagent is used to determine the presence of a reducing sugar, i.e. when a mixture contains sugar it will turn from blue to green to orange to red after this test – an indication that the reducing sugar is present. Fehling’s reagent also has the same result.  If the mixture stays blue, it is a Disaccharide. One can further perform the Modified Barfoed’s test to indicate if the reducing sugar from the Benedict’s test is either Disaccharide or a Monosaccharide. This can be followed by the Seliwanoff’s test to determine if the sugar is a ketose or an aldose sugar. If the sugar is a ketose sugar, the mixture will turn pink while if the sugar is an aldose sugar, the mixture is colourless. In addition one can determine if the sugar is pentose or not by performing the Bail’s test. A positive test results in the mixture turning green while a negative result results in the mixture remaining yellow.

Here I’ve drawn a flow chart for such an experiment involving all possible tests described.

Flow Chart of Carbohydrate Test

Flow Chart of Carbohydrate Test (Credit to the blogger of Biochemology for her help)

I do hope this post was informative and helps with your studies. Good luck!

-Carlos

References

“Nonreducing Sugar.” OChemPal. science.uvu.edu/ochem/index.php/alphabetical/m-n/nonreducing-sugar/ (accessed April 1, 2013).

“Tollen’s Test.” OChemPal. science.uvu.edu/ochem/index.php/alphabetical/s-t/tollens-test/ (accessed April 1, 2013).

“What is the principle of the Fehling’s test.” The Q&A wiki. http://wiki.answers.com/Q/What_is_the_principle_of_the_Fehling’s_test (accessed April 1, 2013).

Pictures

http://12angrymen.files.wordpress.com/2008/06/sucrose.jpg?w=510


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