Properties of Carbohydrates

Carbohydrates have the following properties:

Carbohydrate Physical Properties

 Stereoisomerism - A compound with the same structural formula but a different spatial configuration.

 In the case of glucose, there are two isomers in terms of the last carbon atom. D-glucose and L-glucose are the two sugars.

 Optical Activity: The rotation of plane-polarized light that forms (+) glucose and (-) glucose is known as optical activity.

 Diastereo isomers - These are the configurational variations in glucose with respect to C2, C3, or C4. Mannose and galactose are two examples.

 Annomerism is the spatial configuration of the first carbon atom in aldoses and the second carbon atom in ketoses with respect to the first carbon atom.

Carbohydrate Chemical Properties

The cleavage of biomolecules by adding a water molecule to the separation of a bigger molecule into its component parts is known as biological hydrolysis.

Condensation processes can be reversed by hydrolysis reactions.

Hydrolysis of adenosine triphosphate is associated with energy metabolism and storage. The production of micro and macromolecules, as well as the active movement of ions and molecules across cell membranes, requires a constant supply of energy for all live cells. Pyrophosphate linkages are found in the ATP molecule.

To start, terminal phosphate is removed to create adenosine diphosphate (ADP) and inorganic phosphate:

H + ATP

ADP + Pi = 2O

Second, a terminal diphosphate is removed to create adenosine monophosphate and pyrophosphate.

Amide hydrolysis:

An amide is hydrolyzed in the following way:

A carboxylic acid and an amine or ammonia are formed when an amide is degraded. The amine (or ammonia) gets the hydrogen ion when one of the two oxygen groups on the carboxylic acid is derived from a water molecule. Peptide hydrolysis is the process of breaking peptides into smaller parts.

Polysaccharides hydrolysis:

Amylase enzymes can convert starch to glucose or oligosaccharides by hydrolyzing polysaccharides. Cellulase breaks down cellulose into cellobiose, which is then broken down further by beta-glucosidase into glucose. Because of symbiotic bacteria that produce cellulases, ruminants like cows can hydrolyze cellulose into cellobiose and subsequently glucose.

Carbohydrate Oxidation:

When monosaccharides' carbonyl groups reduce to produce carboxylic acids, they become reducing sugars. D-glucose is oxidised to D-gluconic acid in Benedict's test, proving glucose a reducing sugar.

Aldoses contain functional groups such as alcohol and aldehyde that can be oxidised to carboxylic acids. We can either selectively oxidise the aldehyde or oxidise the main alcohol as well, depending on the oxidising agent. If both groups are oxidised to the same degree,

Mild oxidising agents

These agents are used to distinguish between aldoses and ketoses because the aldehyde, which is more reactive, is converted to a carboxylic acid, whilst the ketone and ethyl alcohol present in both are not. When Br2 is reacted with the aldehyde, its red colour fades, excellent choice for this.

If the monosaccharide is a ketose, the red colour will remain, suggesting that there will be no reaction with Br2.

One thing to keep in mind is that in basic conditions, isomerization between aldoses and ketoses occurs. The Br2 test will yield a good result if the ketose is isomerized to an aldose. To avoid this, the Br2 reaction is usually carried out at a slightly acidic pH (pH = 6).

To induce isomerization, many methods of oxidising both aldoses and ketoses under basic conditions are used:

Reagents that used for carbohydrates oxidation:

Tollens' reagent (Ag+ NH3, HO), Fehling's reagent (Cu2+ in aqueous sodium tartrate), and Benedict's reagent (Cu2+ in aqueous sodium citrate) are the most popular examples of reagents used for carbohydrate oxidation.

Results:

The by-product Ag, which coats the surface of the flask and forms a mirror, is the indicator in Tollens reagent:

When the Cu2+ salt is reduced by the aldose or ketose present in the solution, the Fehling's and Benedict's tests rely on the creation of Cu2O as a red precipitate. By benedict test, reducing sugars are transformed to potent reducing species known as enediols when heated in the presence of an alkali. The colour of Benedict's reagent solution and reducing sugars changes to orange red/brick Red when heated together.

Oxidation using a strong oxidising agent:

Using nitric acid (HNO3), a stronger oxidising agent, to oxidise both the aldehyde and 1o alcohol groups to carboxylic acids (aldaric acid), is a typical method.

Reduction to alcohols:

Sodium borohydride, NaBH4, or catalytic hydrogenation (H2, Ni, EtOH/H2O) can reduce the C=O groups in open-chain carbohydrates to alcohols. The products are referred to as "alditols."

Because of its incompatibility with polar solvents, LiAlH4 is usually not recommended.

Aldehydes are converted to primary alcohols, similar to aldoses.

Ketones are converted to secondary alcohols, just like ketones.

Although the patterns of many carbohydrates appear to be fairly complex, the chemistry of these molecules usually only involves two functional groups: ketone or aldehyde (both of which are polar carbonyl compounds) and alcohol hydroxyl groups.

Carbohydrates are divided into two classes based on their functional groups:

1- Aldoses

2- ketoses

Carbs with an aldehydic functional group are known as aldoses.

Ketoses: those carbs that has a ketonic functional group.

Iron chelation by sugars:

At alkaline pH, reducing sugars and polyols create soluble stable compounds with a series of metal ions. The pH and iron and fructose concentrations necessary for complex formation are explained in detail. At pH 9.0, the complex is constituted of 2 Fe: 2 fructose: 1 Na, according to elemental analysis. At pH 4.5–4.7, it is isoionic.

Osazone formation:

Sugars react with an excess of phenylhydrazine to generate osazone, which are carbohydrate derivatives. Glucosazone is one example.

Conclusion:

 They have a significant structural role in cellulose-based plants.

 Arthropods have a chitin exoskeleton, which is also a carbohydrate.

 Carbohydrates are being used by living organisms to power cellular reactions. They are the most prolific dietary form of energy for all living things (4kcal/gram).

 They're connected to a variety of proteins and lipids. Cell-to-cell communication and interactions between cells and other factors in the cellular environment rely on linked carbohydrates.

 They are a key component of connective tissues in mammals.