Carbohydrates

Carbohydrates, also known as saccharides, are the most numerous class of biomolecules on the planet by far. However, carbohydrates perform a variety of other vital roles in storing energy. Carbohydrates are chemical components in living tissues and foods in starch, cellulose, and sugars. Carbohydrates have the same oxygen to hydrogen ratio as water, which is 2:1. It usually degrades the animal’s body, releasing energy. 

Carbohydrates

Carbohydrates are biochemical molecules made up of carbon, hydrogen, and oxygen in a ratio of one carbon atom (C) to one water molecule (H2O). Carbohydrates are made up of carbon (carbo-) and water, and their name comes from this combination (-hydrate).

Carbohydrates are classified as simple or complex types:

• Simple Carbohydrates

 Simple carbohydrates are found in soft drinks, cookies, and other sweet treats. These foods commonly include white sugar, a processed sugar.

Simple carbohydrates include natural sugars. They originate from fruit, sugar, and anything else sweet. These substances can be easily broken down by the human body, which causes various issues.

• Complex Carbohydrates

Complex carbohydrates are a vital source of energy for your body’s operations. They supply your body with the long-term energy required for exercise, daily activities, and even relaxation and recovery.

Complex carbohydrates are frequently composed of single units (monosaccharides) chemically linked together. The oligosaccharides range from two to ten simple sugar units in their composition. Polysaccharides are made up of hundreds or thousands of monosaccharides connected. Complex carbohydrates provide energy that lasts for a lengthy period.

A carbohydrate is a naturally occurring compound or a derivative of one, that has the general chemical formula Cx(H2O)y and it is made up of carbon (C), hydrogen (H), and oxygen (O) molecules (O). Carbohydrates are the most common chemical components and are required for all living things to exist.

Carbohydrates are broken down by animals (including humans) throughout the metabolic process to release energy. The chemical breakdown of the sugar glucose, for example, is depicted below 

Carbohydrates are obtained by animals eating carbohydrates-containing foods such as potatoes, rice, and bread. Plants produce these sugars as part of the photosynthesis process. Plants use energy from the sun to reverse the reaction described earlier:

Sources of Carbohydrates include fresh fruits, vegetables, corn, potatoes, milk, and milk products. Soda, white bread, artificial sugar, pastries, and other highly processed meals are all unhealthy sources. Sources of carbohydrates can be plant-based as well as animal-based.

Classification of Carbohydrates:

Although there are several classification schemes for carbohydrates, the separation into four primary groups—monosaccharides, disaccharides, oligosaccharides, and polysaccharides—is one of the most widely used. The three most common simple sugars—glucose, fructose, and galactose—all have the same molecular formula (C6H12O6), but their atoms are arranged differently, giving them various properties; thus, they are isomers.

Oligosaccharides

The word oligos come from the Greek word oligos, which means few. They are composed of 2-9 monosaccharide units. For example sucrose, raffinose, etc.

1. Starch(C6H10O5)n

It is a complex carbohydrate and is a polymer of glucose. It turns blue with iodine. This mixture comprises two components.:

1. Amylose (20%)
2. Amylopectin (80%)

Reducing and Non-reducing sugars

Based on their reducing and non-reducing nature, carbohydrates are sorted into reducing and non-reducing sugars. Carbohydrates that can reduce the Fehling reagent or Tollen’s reagent and have free aldehyde or ketone groups attached are known as reducing carbohydrates. e.g., All monosaccharides and disaccharides (except sucrose). But carbohydrates that do not reduce such reagents and do not have free aldehyde or ketone group attached are known as non-reducing carbohydrates. e.g., sucrose and polysaccharides.

Properties of glucose

One aldehyde, one primary hydroxyl (-CH2OH), and four secondary hydroxyls (-CHOH) groups make up glucose. These are the reactions that take place with glucose:

1. i) Glucose on acetylation with acetic anhydride gives a pentaacetate confirming the presence of 5 hydroxyl groups in the glucose.
2. ii) Glucose becomes monoxime when it reacts with hydroxylamine, and cyanohydrin when it reacts with a molecule of hydrogen cyanide

These reactions prove that the carbonyl group is present in glucose.

1. v) Glucose on prolonged heating with HI gives n-hexane, proving that all the carbon atoms in the glucose are linearly bonded.
2. vi) Osazone is generated when D-glucose interacts with three molecules of phenylhydrazine.

Haworth and Hirst gave the cyclic structure of glucose.

Simple sugars

Units of sugar make up all carbohydrates (also called saccharide units). Simple sugars are carbohydrate molecules that contain just one sugar unit (monosaccharides) or two sugar units (disaccharides). Simple sugars have a sweet taste and can be metabolized down in the body to provide energy. Glucose and fructose are two of the most abundant monosaccharides. Although glucose and fructose have the same chemical formula (C6H12O6), their structures are different, as seen in the diagram:

Fructose                         Glucose

Two sugar units are linked with each other in a disaccharide. Sucrose, for example, is a disaccharide that is made up of a glucose unit bonded to a fructose unit:

Molecular structure of sucrose:

Complex Carbohydrates

Simple sugars are polymers, whereas complex carbohydrates are polymers of simple sugars. In other words, complex carbohydrates are long chains of connected simple sugar units (that’s why complex carbohydrates are often referred to as polysaccharides). The complex carbohydrate starch that is mentioned before is found in the potato. Starch is a polymer of glucose, a monosaccharide.

    Starch

Starch- Plants use starch as the primary carbohydrate to store glucose for subsequent usage as energy. Sources of starch include rice, beans, wheat, maize, potatoes, and so on. 

When humans consume starch, an enzyme called amylase, which is found in saliva and the intestines, breaks the connections between the repeated glucose units, allowing the sugar to enter the bloodstream. The human body either transports glucose to the locations where it is needed for energy or saves it as its specific polymer, glycogen, once it has been released into the bloodstream.

Glycogen-It’s a polymer of glucose, it is the energy-storing carbohydrate in mammals. Excess glucose is linked together to produce glycogen molecules, which the animal reserves as an “immediate” source of energy in the liver and muscle tissue. Both starch and glycogen are glucose polymers, however, starch is a long, linear chain of glucose units, and glycogen is a branched-chain, as shown below:

The Glycogen Molecule

Cellulose- It’s also another essential polysaccharide. Cellulose is the monosaccharide glucose’s third polymer. Because the glucose units in cellulose create a two-dimensional framework with hydrogen bonds, the molecule is more stable than starch and glycogen.

Because cellulose, also known as plant fiber, is incapable of being metabolized by humans, it travels through the digestive tract without being absorbed. Even though most animals cannot use cellulose fiber as an energy source, it is necessary for the diet since it serves to exercise the digestive tract and keep it clean and healthy.

The Cellulose Molecule

Conclusion 

Carbohydrates are chemical compounds in which carbon (C) is bonded to hydrogen and oxygen (H2O) in various ratios depending on the carbohydrate. Monosaccharides and disaccharides that are simple sugars and polysaccharides, which are polymers of simple sugars known as complex carbohydrates are the two forms of carbohydrates. Aldehydes or ketones with two or more hydroxyl groups are called monosaccharides. Disaccharides are composed of monosaccharides units bound together by glycosidic linkage. Long chains of monosaccharides are linked together by glycosidic bonds to form polysaccharides.

Our body breaks carbohydrates into glucose. They serve important functions in the human body. 

Starch and cellulose are all examples of complex carbohydrates.