Carbohydrates (simple and complex): what they are, types and what they are for

Carbohydrates, also known as carbohydrates or saccharides, are molecules with a structure composed of carbon, oxygen and hydrogen, whose main function is to provide energy to the body, since 1 gram of carbohydrate corresponds to 4 Kcal, constituting about 50 to 60% of the diet.

Some examples of foods that contain carbohydrates are rice, oats, honey, sugar, potatoes, among others, which can be classified into simple and complex carbohydrates, according to their molecular structure.

What are worth for

Carbohydrates are the main source of energy for the body because, during digestion, glucose is generated, which is the preferred component of cells to produce energy, which break down this molecule into ATP, used in various metabolic processes, for the proper functioning of the body . Glucose is mainly used by the brain, which uses about 120 g, out of a total of 160 g used daily.

In addition, a portion of the glucose generated is stored in the form of glycogen in the liver, and a small portion is stored in the muscles, for situations in which the body needs reserves, such as in situations of prolonged fasting, alertness or metabolic stress , for example.

The consumption of carbohydrates is also important for the preservation of muscles, since the lack of glucose favors the loss of muscle mass. Fiber is also a type of carbohydrate, which, despite not being digested in glucose, is essential for the digestion process, since it decreases the absorption of cholesterol, helps maintain blood sugar, increases bowel movements and favors the increase the volume of stool, avoiding constipation.

Is there another source of energy besides glucose?

Yes. When the body uses glucose reserves and there is no carbohydrate intake or when the intake is insufficient, the body begins to use the body's fat reserves to generate energy (ATP), replacing glucose with ketone bodies.

Types of carbohydrates

Carbohydrates can be classified according to their complexity, into:

1. Simple

Simple carbohydrates are units that, when joined together, form more complex carbohydrates. Examples of simple carbohydrates are glucose, ribose, xylose, galactose and fructose. When consuming a portion of carbohydrate, this more complex molecule decomposes at the level of the gastrointestinal tract, until it reaches the intestine in the form of monosaccharides, to be later absorbed.

The union of two units of monosaccharides form the disaccharides, such as sucrose (glucose + fructose), which is table sugar, lactose (glucose + galactose) and maltose (glucose + glucose), for example. In addition, the union of 3 to 10 units of monosaccharides gives rise to oligosaccharides.

2. Complexes

Complex carbohydrates or polysaccharides are those that contain more than 10 units of monosaccharides, forming complex molecular structures, which can be linear or branched. Some examples are starch or glycogen.

What are carbohydrate foods

Some foods rich in carbohydrates are bread, wheat flour, french toast, beans, lentils, chickpeas, barley, oats, cornstarch, potatoes and sweet potatoes, for example.

The excess of carbohydrates is deposited in the body in the form of fat, so, although they are very important, one should avoid ingesting in excess, being recommended an intake of about 200 to 300 grams per day, which is an amount that varies according to weight, age, sex and physical exercise.

See more carbohydrate-rich foods.

How carbohydrate metabolism happens

Carbohydrates intervene in several metabolic pathways, such as:

• Glycolysis: is the metabolic pathway in which glucose is oxidized to obtain energy for the body's cells. During this process, ATP and 2 pyruvate molecules are formed, which are used in other metabolic pathways, to obtain more energy;
• Gluconeogenesis: through this metabolic pathway, glucose can be produced from sources other than carbohydrates. This pathway is activated when the body goes through a prolonged fasting period, in which glucose can be produced through glycerol, from fatty acids, amino acids or lactate;
• Glycogenolysis: it is a catabolic process, in which the glycogen that is stored in the liver and / or in the muscles is broken down to form glucose. This pathway is activated when the body requires an increase in blood glucose;
• Glucogenesis: it is a metabolic process in which glycogen is produced, which is composed of several glucose molecules, which is stored in the liver and, to a lesser extent, in the muscles. This process occurs after eating foods with carbohydrates.

These metabolic pathways are activated depending on the needs of the organism and the situation in which it finds itself.

Was this information helpful?

Yes No

Your opinion is important! Write here how we can improve our text:

Any questions? Click here to be answered.

Email in which you want to receive a reply:

Check the confirmation email we sent you.

Your name:

Reason for visit:

--- Choose your reason --- DiseaseLive betterHelp another personGain knowledge

Are you a health professional?

NoMedicalPharmaceuticalsNurseNutritionistBiomedicalPhysiotherapistBeauticianOther

Bibliography

• MAHAN, L. Kathleen et al. Krause: Food, Nutrition and Diet Therapy. 13.ed. São Paulo: Elsevier Editora, 2013. 33-39.
• NELSON David and COX Michael. Lehninger Principles of Biochemistry. 7th. São Paulo, Brazil: Artmed, 2019. 241-272.