Why glycogen is not a reducing sugar

We then added the Benedict's reagent. We got moderately positive results orangish color. This is because HCl breaks starch back down into its component monosaccharides glucose, in this case. Amylase is an enzyme that removes glucose molecules from starch. Both plants and animals use amylase when digesting starch. Unfortunately, amylase cannot break the beta-bonds which hold the glucose molecules together in cellulose.

If it could, we'd be able to eat hay. Based on this information, can you figure out what our results should be if we tested amylase-treated starch and amylase-treated cellulose solutions for reducing sugars? Organic Molecules These are complex, carbon-containing molecules associated with living organisms. Most also contain hydrogen and oxygen. There are five major types: carbohydrates, lipids, proteins, nucleic acids, and vitamins.

We covered the first three types in lab. A review of our carbohydrate test data is provided on this page. Click the molecule types above to link to the associated review material.

Interpreting Benedict's Reagent Results Benedict's reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange.

The "hotter" the final color of the reagent, the higher the concentration of reducing sugar. Carbohydrate chains contain aldehyde or ketone functional groups, which are types of carboxyl groups. Remember the general formula for a carbohydrate is: since they are hydrates water of carbon. Which of the following is not an example of a compound that contains carbohydrate in its structure?

To identify the answer choice that is NOT a polysaccharide, let's go delve into each answer choice a bit. Cellulose is a polysaccharide and also a very important component of the cell wall of plants. It consists of many glucose sugars bound together via beta linkages. Peptidoglycan is also a polysaccharide and a very important component of the cell wall of bacteria.

Its structure consists of alternating N-acetylglucosamine and N-acetylmuramic acid connected via beta linkages. Both of these are modified sugar molecules. Chitin is a polysaccharide that plays an important role in the structure of the exoskeleton of many fungi, arthropods, and insects.

Its structure consists of a long chain of N-acetylglucosamine, which is a derivative of the sugar glucose. Collagen is the only answer choice that does not represent a carbohydrate. Rather, collagen is a protein that plays a very important role in the extracellular matrix of various connective tissues found in animals. Glycogen is a branched form of glucose that is the storage form in animals. It contains beta and beta linkages.

Both cellulose and starch are polymers of glucose; why can't and enzyme that breaks down starch also break down cellulose? Cellulose is composed of cyclic glucose molecules while starch is composed of linear glucose molecules. Glucose monomers in starch are double bonded together while they are connected by single bonds in cellulose. Cyclized monosaccharides can exist in two different stereoisomers that depend on the orientation of the hydroxyl group on the anomeric carbon. If this group is on the opposite side of the ring as the group, the sugar as the alpha anomer.

The opposite orientation is referred to at the beta anomer. Cellulose is a polymer of beta glucose while starch is a polymer of alpha glucose, and the bonds between these glucose monomers differ depending on their anomer.

This makes it so an enzyme can recognize one or the other but not both. Note that D-sugars are biologically relevant. A glycosaminoglycan GAG is a long, unbranched polysaccharide that consists of many repeating disaccharide units. Dermatan sulfate, keratan sulfate, hyaluronate, and heparin are all examples of glycosaminoglycans. Erythropoietin, however, is a glycoprotein hormone that stimulates production of red blood cells. If you've found an issue with this question, please let us know.

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Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney. Hanley Rd, Suite St. Louis, MO Subject optional. Email address: Your name:. Biochemistry Help » Biochemistry. Example Question 4 : Glycosidic Linkages. Possible Answers: Branching increases glycogen solubility. Branching increases the rate of glycogen degradation. Branching increases the rate of glycogen synthesis.

All of these are reasons why glycogen branching is important. Correct answer: All of these are reasons why glycogen branching is important. Explanation : Because glycogen is so heavily branched, it is able to pack more glucose units together in a small space, thus it is more compact and has a greater solubility. Report an Error. Example Question 5 : Glycosidic Linkages.

Possible Answers: Glucose-beta 1,4-glucose. Correct answer: Galactose-beta-1,4-glucose. Explanation : lactose is made up of galactose and glucose and is bound via a beta 1,4 glycosidic bond. The first three lines below describe the procedure. Silver nitrate is converted to silver hydroxide, which forms silver I oxide, Ag 2 O. Then, addition of aqueous ammonia NH 3 results in formation of the silver-ammonia complex which is the active oxidant. The sample to be tested is then added to the freshly prepared active oxidant in a basic solution.

A positive test results in a beautiful mirror of silver metal being precipitated out on the reaction vessel. A variant of this procedure is used for the preparation of mirrors. Bottom line here is that adding base has the effect of increasing the concentration of the starting aldehyde. If I am wrong, please tell me leave a comment. One of the access points for the initiation of a single-electron transfer reaction is a carbon-metal bond, which can be achieved through base-promoted formation of an enolate.

That requires that the aldehyde have a proton on the alpha carbon i. Thus it would appear that the reaction needs to proceed through an enol. Hover here for a pop-up image or [ click for image of a hypothetical mechanism ]. Image sources: Benedicts solution. Tollens test. Note 1. The standard way to do it is the Pinnick oxidation.

Note 2. The quantitative test apparently employs potassium isocyanate, which results in a colourless precipitate. See the mechanism section. Note 4. A very enjoyable post! In the 4th reaction, the charge is on the oxygen; this is preferable. What if a product contains high percentage of reducing sugar?

What does it denotes? I have prepared a product which contains Thank you very much for your posts they are very helpful.

Blessings and thanks again! And thanks again for your very clear explanations. I have a question regarding reducing sugars as excipients with drugs. Some carbohydrates reducing sugars form covalent bonds with drugs that contain primary and secondary amines.

So I have been looking at the Maillard reaction which breaks down the hydroxyl group of a reducing sugar and then forms Amadori products. I have been searching for a reaction mechanism for the Amadori adduct formed from dexamphetamine and lactose. I was wondering if you could perhaps give a generic mechanism or a similar example.

I note you give two examples of lactose and maltose as disaccharides that are reducing sugars as they contain the hemiacetal. I was wondering if you could give a general mechanism reacting with a primary amine such as R-NH2?. This website is phenomenal. Ashenhurst teaches these topics so much better than they do at school! Keep up the great work! Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

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