The carbohydrates are chemicals consist of carbon, hydrogen and oxygen, which are found in abundance in nature. They have also been called carbohydrates , but they do not fulfill the characteristic of holding complete water molecules (H 2 O) in their composition, like hydrates.Rather, carbohydrates are chains of aldehydes or ketones with various hydroxyl groups (-OH). They are characterized by being one of the main sources of energy for living beings , since when their molecules decompose, they are capable of providing 4 kilocalories for each gram of substance. Carbohydrates are introduced into the body through diet for this purpose.

Carbohydrates, also called sugars , can be simple molecules or groups of these, and are found naturally in plant species as part of their composition. Animals take them for their organisms by ingesting plants and their fruits . The human being can obtain them in this way and also as products of industrial processes .

Carbohydrates are used to:

  • The plant nutrition
  • Get energy for the body
  • Prepare dishes and desserts
  • Synthesize alcohols

The plant nutrition

The most abundant carbohydrate and the basis of most molecules is glucose , whose condensed formula is C 6 H 12 O 6 . It is known by other names such as grape sugar , dextrose, or blood sugar . Glucose is obtained by plants through the natural process of photosynthesis . The reaction mechanism to form glucose is as follows:

6 CO 2 + 6 H 2 O + Energy -> C 6 H 12 O 6 (glucose) + 6 O 2

It is in this way that a double benefit is achieved: plants feed and human beings receive the oxygen load that renews the air we breathe.

Plants, after using a certain amount of glucose to survive, use the remainder to form their plant tissues and structurally reinforce them. They form the so-called cellulose , which is a carbohydrate made up of long chains of glucose molecules.

The cellulose is the carbohydrate forming the cell walls and tissues of plants. It is also the raw material to make paper and chemical products such as nitrocellulose .

Carbohydrates are used to obtain energy for the body

Some carbohydrates can be obtained from fruits.

The human being and other mammals, in their diet, are provided with carbohydrates such as:

  • Sucrose C 12 H 22 O 11 : also called table sugar.
  • Lactose C 12 H 22 O 11 : also called milk sugar, with the same formula as sucrose, but different arrangement of the atoms in its molecule.
  • Maltose C 12 H 22 O 11 : also called malt sugar, found in grains; It has the same formula as sucrose and lactose, but a different arrangement of the atoms in its molecule.
  • Starch (C 6 H 12 O 5 ) n : is a complex carbohydrate (a polysaccharide) made up of many glucose molecules, found in tubers such as potatoes.

The body is capable of transforming these sugars into glucose, which is oxidized for energy. One gram of glucose is capable of providing 4 kilocalories .

In the case of mammals, the excess glucose that is not used as energy is transformed into glycogen , a carbohydrate made up of a long chain of glucose, and that functions as a “glucose reserve” so that it is transformed back into glucose and obtained energy from it later, if required.

Prepare dishes and desserts

Carbohydrates such as sucrose (table sugar) and fructose (fruit sugar) are characterized by giving a sweet taste to foods such as:

  • Fruit salad
  • Cake shop
  • Cakes
  • Nuts
  • Drinks

The sucrose is removed from the rod, so that also is called cane sugar . Its tiny crystals are added to the mixture of all the ingredients of the dish or dessert that is going to be prepared, and the result is a sweet food.

Caution must be exercised in the consumption of sucrose , because it considerably raises the level of glucose in the blood. The body secretes insulin through the pancreas, and with it counteracts excess glucose . However, when this carbohydrate is too much and insulin is not enough, diabetes occurs .

The fructose is contained naturally in fruits. It is enough to put them as ingredients of the dish so that it is left with a pleasant and sweet flavor. It is beneficial to consume it for energy, without directly resorting to table sugar or sucrose.

Synthesize alcohols

Alcohols can be prepared from carbohydrates.

When carbohydrates undergo a fermentation process, alcohols are obtained from them. In this process, organisms such as yeast (microscopic fungi, such as Saccaromyces cerevisiae ) oxidize polysaccharides to convert them into glucose, and later this is oxidized to separate it into ethanol or ethyl alcohol molecules: C 2 H 5 OH .

This is the way that alcoholic beverages like beer are prepared and develop their alcohol content. Other larger molecule alcohols can be synthesized by a variety of other reaction mechanisms.

Classification of carbohydrates

Carbohydrates, according to the size of their molecules, are classified as follows:

  • Monosaccharides or simple sugars
  • Disaccharides (from monosaccharide molecules)
  • Trisaccharides (three monosaccharide molecules)
  • Tetrasaccharides (four monosaccharide molecules)
  • Pentasaccharides , (five monosaccharide molecules), and so on with numerical prefixes, up to Decasaccharides , with ten monosaccharide molecules.
  • Polysaccharides (more than ten monosaccharide molecules)

Monosaccharides, according to the chemical nature of their molecules, are classified:

  • Aldosas
  • Cetosas

The suffix -ose is used in the systematic nomenclature of carbohydrates to indicate a sugar with an aldehyde group or an alpha-hydroxyketone group. They are also called reducing sugars .

The aldoses , in turn, according to the number of carbon atoms in their molecule, are classified:

  • Aldopentoses (five carbon atoms), such as ribose
  • Aldohexoses (six carbon atoms), such as glucose

The ketoses , in turn, according to the number of carbon atoms in the molecule, are classified:

  • Ketopentoses (five carbon atoms), such as ribulose
  • Ketohexoses (six carbon atoms), such as fructose


Samantha Robson
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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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