Diet and Nutrition

Is Glucose a Carbohydrate?

Understand what glucose is and how it affects your body, weight and health.


The main source of energy for most of the world’s population is carbohydrate. In many pre-prepared foods this is the main ingredient. Mostly carbohydrates are classified based on chemical structure. Monosaccharide, disaccharides and polysaccharides are types of carbohydrates. Oligosaccharides are also one type but they are not known very well. Raffinose and insulin are oligosaccharides and they are short chain carbohydrate. The enzymes are not able to digest them hence in the large intestine they are fermented by bacteria.

Almost all forms of carbohydrates come from plant foods excepting lactose that comes from milk and specific forms of carbohydrates that comes from red meat.


The most universal building block of carbohydrate is glucose. For production of new cells and as a source of energy the living cells of the body assimilates this glucose. This function of glucose explains why in the pool of free saccharides in lake water thee glucose quantity keeps reducing. Glucose plays a very versatile role in human body. Glucose is present in phytoplankton and other carbohydrates found are cellobiuose, arabinose, fucose, rhamnose, fructose and melibiose.

Function of carbohydrate

For energy the body prefers carbohydrate. Our daily food is majority made of carbohydrates. In almost all forms of foods carbohydrates are present such as flour, cereals, potatoes, pasta, grain flour and vegetables. In the form of sugar, they are present in candy, honey, syrups and fruits. Our food consists of the element carbohydrates whose functions are as follows:

For automatic activity of our body it provides energy. Also it enables the body to perform daily tasks.  We must consume more carbohydrates if we perform more of physical task.

In protein and fat digestion, assimilation and oxidation carbohydrates play an important role.

Generally, it is believed that main source of carbohydrates is grains. But many other sources provide us carbohydrates along with other important nutrients. Main source of carbohydrates comes from plants but it is also present in milk and milk products in the form of lactose.

Carbohydrates provide our body energy quickly, for all living things it is the basic source of energy. In fruits, vegetables it is present and all the forms of carbohydrates are ultimately broken down to glucose. Sometimes glucose is also known as grape sugar and it is especially found in saps and fruits.  Apart from glucose other simple carbohydrates are sucrose, fructose, maltose and lactose. –

The energy and the nutrients that the body needs are provided by the complex carbohydrates. Starch is a complex carbohydrate and it is broken down to simple sugars.  Plants are a source of starch. The other complex carbohydrate is dietary fiber which is also found in plants.

Glucose a carbohydrate

The most common carbohydrate is glucose and it is classified as a hexose, an aldose and a monosaccharide. Glucose is also a reducing sugar. Since it is dextrorotatory it is considered to be dextrose. Since at a concentration of 65 to 110 mg per dL it circulates in the blood hence it is called as glucose. Plants from the air use carbon dioxide and sunlight is used as source of energy and by using chlorophyll glucose is synthesized. Further for storage this glucose is converted to starch.

Glucose is a monosaccharide which means one sugar. Glucose is one common form of monosaccharide.  The glucose has a cyclic structure and is made of carbon, hydrogen and oxygen. Mainly glucose exists as a cyclic compound but to a smaller extent it is found in equilibrium with its linear forms too. The body gets basic fuel from this carbohydrate. Glucose is also known as blood sugar and in the bloodstream dextrose flows so that every cell in the body gets energy. Glucose is absorbed by the cells and to drive the cell this glucose provides them energy. ATP is created when glucose undergoes chemical reactions. Most of the functions of the human cell are enabled by the phosphate bond present in the ATP. Glucose is directly absorbed by the body and it enters into the bloodstream. The main sugar the body metabolizes is the sugar glucose which is used as a source of energy. In nature the D isomer form of glucose predominates. Hence mostly this form of glucose only binds with the enzymes. Starch is the main source of glucose in our body and in plants this form of glucose is stored.

Glucose is a carbohydrate made of carbon and water. The glucose is composed of six carbon atoms and it consist six water molecules. The taste of glucose is sweet since it is a simple sugar. The other sugars apart from glucose are fructose which is found in fruits. This fructose is converted to glucose by the liver. Another sugar is sucrose which is bonded together by one molecule or glucose and one molecule or fructose. Another sugar is lactose which is bonded together by one molecule of glucose and one molecule or galactose. Even galactose is converted to glucose by the liver. Another sugar is maltose which is present in malt and it is formed by two glucose molecules. Through the intestinal lining directly into the blood glucose and other sugars such as fructose and galactose are absorbed.

Glucose is also known as dextrose. It is a kind of carbohydrate and it is found in fruits and honey. In the blood of higher animals mostly this free sugar circulates. In functioning of the cell this glucose is a source of energy and regulates the metabolism. Hence it is of great importance to the body. There are thousands of linear glucose units in starch which is a form of carbohydrate stored as energy in plants. Cellulose is another linear compound made of glucose. The D glucose form is known as dextrose.

Related to glucose is another molecule known as glycogen. In most vertebrates and invertebrates, in some fungi and protozoans this carbohydrate reserve is found. In human metabolism glucose is the most important simple sugar. Since it has the characteristics of the class of carbohydrates and is one of the smallest units hence it is called as simple sugar. One of the glucose is corn syrup. In plants and animal’s glucose serves as a source of energy. Also in the human bloodstream and in the sap of plants this carbohydrate is found.  About 0.1 percent of glucose is found in the human blood but in people suffering from diabetes the percentage is much higher.

Carbon dioxide, water and nitrogen compounds are formed when glucose is metabolized in the body. By this metabolisation energy is produced which is used by the cells. About 686 kilocalories of energy is yielded per mole which enables the body to remain warm and also to do work.

In the human body when glucose is oxidized it leads to a series of complex biochemical reactions through which the cells get energy. Glycolysis is the first step in which glucose is broken down in the cells and pyruvate is produced. For processes occurring in cellular respiration pyruvate is the starting point. When ADP is converted to ATP a major part of the energy is used from the process of glucose oxidation and subsequently as energy currency of the cell the ATP molecule is used.

In the process of photosynthesis glucose uses energy from the sun. In chloroplasts present in the plant leaves glucose is synthesized. The energy from the light is captured by the chloroplasts and glucose molecules are fabricated by using carbon dioxide and water.

In liner form glucose can be found.

Why is glucose important?

For almost everything, we need glucose. When glucose undergoes chemical reaction energy is produced which is used by the body. One molecule of glucose consists of glucose, hydrogen and oxygen. Many sources of food contain glucose. Bread, pasta, rice contains glucose. They are the main source of energy. Other carbohydrates are broken down to glucose in the process of digestion. The level of blood sugar is the quantity of glucose present in one liter of blood. Mostly at around one gram of glucose per liter the body is able to effectively control this level. However, the blood sugar level cannot be controlled in people with diabetes. Serious health issues can arise when the levels are too high or too low.

Ring structure

Till recently glucose structure was presented in the form of chain. In an aqueous sugar solution, the chain form of glucose is only 0.2 percent and most of the structure is present in the cyclic chain form. Since functional groups such as alcohol, aldehyde and ketone are present in the carbohydrates thus easily hemiacetal ring structure chain form is obtained by converting the straight chain form.

Types of carbohydrate in the diet

In the form of calories, carbohydrates as a component of food supply energy to the body. Carbohydrates is a macronutrient and the other macronutrients are proteins and fats. For the survival of the body these macronutrients are important. In different proportion these macronutrients are present in our foods. Foods such as grains, pasta, cereals, fruits, bread and pastries are examples of foods that contain this macronutrient. In food different types of carbohydrates are found. These are of two types high quality and low quality carbohydrates. Now a day’s carbohydrate that are of low quality have become more popular and hence have earned bad reputation but it is important to understand that not all carbohydrates are bad. One should incorporate them in their diet in a healthy manner.

Carbohydrates found in food are of three basic types and these are sugars, starches and Fibre. Simple sugars such as glucose are also known as simple carbohydrates. Others are fructose and galactose. These simple sugars are also known as monosaccharides. When monosaccharides unit then disaccharides are formed. They are made of fructose, lactose and glucose molecules.

In many plants carbohydrates are naturally occurring. They contribute to overall health by providing variety of nutrients. Fruits, whole grains, vegetables and legumes are high quality carbohydrates. In processed foods we find low quality carbohydrates. They contain fat, added sugar, sodium and preservatives. These are added so that the shelf life may improve or taste may improve. Even though these processed foods are fortified with vitamins but important nutrients are lacking in them. In this category are foods such as white bread, cereals, sweetened beverages and baked goods.

According to research the healthy diet is contributed and impacted by the quality of carbohydrate that is ingested. Just reducing the carbohydrate will not help. For example when low quality carbohydrates are ingested they cause the blood sugar to rise since these are quickly digested bi the body and the feeling of fullness is temporary. The conversion of starches and sugars to glucose can be offset by the fibers and nutrients present in the whole food which will satiate the appetite and also prevent drastic increase the blood sugar.

Hence choosing more whole grains will help to improve the carbohydrate quality, foods that have added sugar should be taken in limited quantity. Rather than processed foods eat whole foods which will help the overall health significantly.

How is glucose related to carbohydrate?

In food a type of sugar known as glucose is found. The other two types are galactose and fructose. Longer chains of sugars are formed when these two forms combine with each other and with glucose. The carbohydrates found in our body are made of these chains of sugars. These carbohydrates are broken down into chains by proteins and further they are broken down into smaller sugar components. Simple sugars quickly get digested and thus the blood sugar level increases drastically. Apart from simple carbohydrates there are also complex carbohydrates and they are found in whole grains such as in brown rice. These do not digest fast and hence for long time give a feeling of fullness to the stomach.

Carbohydrates are converted into glucose when they are digested and sent into the bloodstream. All the cells obtain energy by glucose. If there is excess glucose, then in the liver and muscles this glucose will be stored as glycogen.

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