Carbohydrates, Chemistry tutorial


The carbohydrate is a big biological molecule, or macromolecule, comprising merely of carbon (C), hydrogen (H) and oxygen (O), generally having hydrogen: oxygen atom ratio of 2:1. Carbohydrates are theoretically hydrates of carbon; structurally it is more precise to view them as the polyhydroxy aldehydes and ketones.

Define: The Carbohydrates are polyhydroxy aldehydes or ketones, or compounds which can be hydrolyzed to them. Carbohydrate is the organic compound including just carbon, hydrogen and oxygen, generally having hydrogen: oxygen atom ratio of 2:1 (as in water). Carbohydrates are theoretically hydrates of carbon. The empirical formula is as: Cn(H2O)n.

Carbohydrates are most likely the richest and prevalent organic substances in nature and they are necessary constituents of all the living things. Carbohydrates are prepared by green plants from carbon-dioxide and water throughout the procedure of photosynthesis. Carbohydrates serve organisms as energy sources and as the necessary structural components; in addition, part of the structure of nucleic acids that include genetic information, comprises of carbohydrate.

Role of Carbohydrates:

The principle roles of carbohydrate in the body comprises providing energy for the working muscles, providing fuel for the central nervous system, allowing fat metabolism and preventing protein from being utilized as energy. Carbohydrate is the favored source of energy or fuel for muscle contraction and biologic work.

Foods having carbohydrate are in the fruit, grains and milk groups. Vegetables encompass a small amount of carbohydrate.

After carbohydrate is eaten, it is broken down to smaller units of sugar (that is, comprising glucose, fructose and galactose) in the stomach and small intestine. Such small units of sugar are absorbed in the small intestine and then enter the blood-stream where they travel to the liver. Fructose and galactose are transformed to glucose by the liver. Glucose is the carbohydrate transported via the bloodstream to the different tissues and organs, comprising the muscles and the brain, where it will be employed as energy.

If the body doesn't require glucose for energy, it stores glucose in the liver and the skeletal muscles in a form termed as glycogen. If glycogen stores are full, glucose is stored as fat. Glycogen stores are employed as an energy source when the body requires more glucose than is readily available in the bloodstream (for illustration, all through exercise). The body has restricted storage capacity for glycogen (around 2000 calories), that is why carbohydrate is generally termed to as the limiting fuel in physical performance.

Carbohydrate spares the utilization of protein as the energy source. Whenever carbohydrate utilization is insufficient, protein is broken down to prepare glucose to maintain a constant blood glucose level. Though, if proteins are broken down they lose their main role as building blocks for muscles. Moreover, protein breakdown might outcome in an increased stress on the kidneys, where protein byproducts are excreted to the urine.

Lastly, glucose is necessary for the central nervous system. The brain mainly employs glucose as its energy source and a lack of glucose can yield in dizziness, weakness and low blood glucose (that is, hypoglycemia). Reduced blood glucose throughout exercise reduces performance and could lead to mental and also physical fatigue.

Carbohydrates in the Diet:

Carbohydrates serve as the main energy source in the diet and give 4 calories per gram of carbohydrate. The Carbohydrates exists in numerous forms, which can be categorized into mainly two groups; simple and complex carbohydrates.

1) Simple carbohydrates are as well termed as simple sugars and encompass a smaller structure.

a) Some of the common simple carbohydrates comprise sucrose (that is, sugar found in candy, juice, soda and so on), and lactose (that is, sugar found in the milk).

b) Simple carbohydrates are readily broken down and absorbed in the intestine to the blood stream. This fast increase in blood glucose leads to the rapid discharge of insulin which is required to assist transport the sugar to the cells.

c) Energy is speedily produced however only lasts for a short time period.

2) Complex carbohydrates are as well termed as starch and fiber and encompass a larger structure.

a) Several common foods having complex carbohydrate comprise pasta, bread and whole grains.

b) The complex carbohydrates take a longer time to digest and absorb. This makes a slow and steady increase in blood glucose and a slow and steady raise in insulin levels.

c) Energy is slowly generated, not as fast as simple carbohydrates; though, the energy lasts for a longer time period.

d) Fiber is a complex carbohydrate, and can be categorized as soluble or insoluble. Soluble fiber can be broken down and gives energy. Soluble fiber is found in numerous fruits and vegetables comprising green leafy vegetables, carrots, celery, apples, pears, among others. The insoluble fiber can't be digested in our digestive system, and doesn't supply energy. Insoluble fiber is generally found in the whole grain cereal, rice and bread. Insoluble fiber consists of a significant role in health via promoting gut motility and satiety.

Sources of Carbohydrates:

Baked goods generally have dietary starch and added sugar. Most of the dietary carbohydrates come from plants. Sugars and starches are nutritive carbohydrates, meaning they are broken down and used by the body, mainly to produce energy. However, dietary fiber is as well a carbohydrate, it contributes no calories as it is not digested or absorbed.

1) Grain Products:

Grain products are the primary source of carbohydrates in the diet. Grains naturally have high concentrations of starch that our gastrointestinal system breaks down to sugars. Common grains in diet comprise wheat, rice, oats, barley and cornmeal. Any food which comprises grain or grain flour as a main ingredient includes carbohydrates, like bread and other baked goods, cereal, pasta and crackers. Selecting whole-grain products rather than those made up from refined grains boosts your dietary fiber intake that supports your heart and digestive health.

2) Starchy Vegetables and Beans:

Beans and starchy vegetables, like potatoes, green peas, yams and corn, have high levels of complex carbohydrates that our body digests to sugars. Moreover, starchy vegetables and beans contribute vitamins, minerals and fiber to our diet. The dry beans as well serve up as a good source of lean dietary protein.

3) Fruits:

All the fruit and fruit juices include carbohydrates in the form of natural sugars, like glucose and fructose. Fruit sugars contribute almost all of the calories contained in such foods. By persistently low consumption rates, fruit contributes less than 8 % of the average daily calories in the diet. Fresh fruit is a healthier choice than fruit juice as it gives more dietary fiber and less carbohydrate by means of volume.

4) Beverages:

Dairy milk is the mere important source of dietary carbohydrates not derived from the plants. A cup of unflavored milk includes around 11 to 12 grams of carbohydrate in the form of milk sugar or lactose. Chocolate milk includes more than two times the amount of carbohydrate per cup as compared to plain milk as sugar is added to sweeten the flavor. Sugar-sweetened soda, fruit drinks and sports and energy drinks considerably contribute to the dietary carbohydrate intake. Wine, beer and liqueurs as well have carbohydrates. Dessert wines generally include roughly four times the amount of carbohydrates found in the table-wines.

5) Sweets and added Sugars:

Eating candy and desserts markedly boost up the number of carbohydrates in our diet. Indulging in a 1.6-ounce milk chocolate bar adds more than 26 grams of carbohydrates to our day by day intake; a slice of cherry pie adds around 47 to 69 grams. Sugar added to processed foods which you might not consider sweet can be an unrecognized source of carbohydrates in our diet. Commercial pasta sauces, sandwich bread, salad dressings, energy and nutrition bars, cereals, heat and-eat meals and other ease foods generally have high-fructose corn syrup or the other form of sugar for added flavor. Opting for whole, fresh foods instead of processed foods assists us avoiding unseen carbohydrates.

Classification of Carbohydrates:

Carbohydrates are categorized into following classes based on whether these undergo hydrolysis and if so on the number of products forms: Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides.

1) Monosaccharides:

The molecules having just one actual or potential sugar group are termed as monosaccharides. They are simple carbohydrates which can't be hydrolyzed further to polyhydroxy aldehydes or ketone unit

Sugars having aldehyde group are known as aldoses and sugars having keto group are known as ketoses. Based on the number of carbon atoms monosaccharides are termed as triose (C3), tetrose (C4), pentose (C5), hexose (C6), heptose (C7) and so forth.

Monosaccharide categorization based on the number of carbons:

No. of Carbons   Category Name    Examples

4                         Tetrose                   Erythrose, Threose

5                         Pentose                  Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose

6                         Hexose                   Allose, Altrose, Fructose, Galactose, Glucose, Idose,

                                                          Mannose, Gulose, Sorbose, Talose, Tagatose                        

7                         Heptose                  Sedoheptulose, Mannoheptulose


2) Disaccharides:

Whenever two monosaccharides are joined altogether with the removal of water molecule it is known as disaccharide. Monosaccharides are joined by glycosidic bond.

Disaccharide   Description                         Component monosaccharides

Sucrose          common table sugar               glucose α1→2 fructose

Maltose          product of starch hydrolysis    glucose α1→4 glucose

Trehalose       found in fungi                           glucose α1→1 glucose

Lactose           main sugar in milk                    galactose β1→4 glucose

Melibiose         found in legumes                     galactose β1→6 glucose

3) Oligosaccharides:

Oligosaccharides that comprise of three to six monosaccharide units are somewhat infrequently found in the natural sources; however some plant derivatives have been recognized.

4) Polysaccharides:

Polysaccharides (that is, the word signifies many sugars) stand for most of the structural and energy-reserve carbohydrates found in the nature. Large molecules which might comprise of as many as 10,000 monosaccharide units linked altogether, polysaccharides differ significantly in size, in structural complexity, and in the sugar content; several hundred distinct kinds have therefore far been recognized. Cellulose, the main structural component of plants, is a complex polysaccharide including lots of glucose units linked altogether; it is the most general polysaccharide. The starch found in plants and the glycogen found in animals as well is complex glucose polysaccharides. Starch (that is, from the Old English term stercan, stand for 'to stiffen') is mostly found in roots, seeds and stems, where it is stored as an available energy source for the plants. Plant starch might be processed into such foods as bread, or it might be used directly - as in potatoes, for example. Glycogen that comprises of branching chains of glucose molecules is prepared in the liver and muscles of higher animals and is stored as the energy source.

Carbohydrate Deficiency Diseases:

The Carbohydrates are being shunned via health conscious, instead weight conscious, people. They have to comprehend those carbohydrate deficiency diseases and their manifestations are certain to appear if there is too much exclusion of carbohydrates in the diet. The entire sources of food do have carbohydrates, even in animal products. Though, the carbohydrate level is extremely low in foods of animal origin with the exception of milk that includes good amount of lactose sugar.

Causes of carbohydrate deficiency diseases:

Generally, whenever balanced diet is used, carbohydrate short fall doesn't occur. If individuals undertake crash-dieting to accomplish rapid weight loss via nutritional deprivations of carbohydrates, no doubt they might lose weight drastically in a short period of time. Though, they might not be able to resist the cravings for the carbohydrates and soon via reverting to old food habits end up gaining weight. In case they are capable to continue dieting, they might have to face numerous carbohydrate deficiency disease manifestations. People lacking food of plant origin, and people suffering chronic illness, poverty or starvation as well experience deficiency diseases.

How does carbohydrate deficiency take place?

The carbohydrates utilized by us are broken down via digestive enzymes into monosaccharides (that is, glucose, fructose and so on) and absorbed in the intestine. Once in the blood, the glucose is employed for energy production. The surplus glucose is taken to the liver and transformed into glycogen for storage. If energy requirement arise, glycogen is broken down and transformed back to glucose. By carbohydrate deprivation in food, the blood glucose, and also the stored glycogen are depleted. In the absence of the availability of glucose for energy production, fats and amino acids (that is, fundamental components of proteins) are used for energy. Though, this route of energy production yields in acidosis, ketosis and loss of the cellular proteins. Prolonged deprivation leads to the symptoms and diseases related with rigorous carbohydrate short fall.

Symptoms and manifestations of carbohydrate deficiency:

The symptoms comprise hypoglycemia, tremor, confusion, feverishness, fatigue, giddiness, distress, muscles atrophy, delirium, loss of muscle tissue and decrease stamina.

Acidosis: In the carbohydrate starvation, there is a shift from glycolysis (that is, breakdown of glucose) to lipolysis (that is, breakdown of lipids) and ketogenesis for energy requirements. The resulting production of ketoacids raises acidity in the blood and other body tissues. Such modifications in the pH of arterial blood outside 7.35 pH to 7.45 pH yield in the irreversible cell damage.

Ketosis: Throughout prolonged carbohydrate fasting or starvation, acetyl-CoA in the liver is employed to produce ketone bodies made by the breakdown of fatty acids and via the deamination of amino acids, leading to the state of ketosis.

Hypoglycemia: The non availability of glucose because of severe lack of carbohydrate causes drop in the blood sugar levels. The Hypoglycemia takes place whenever blood glucose, levels drop below 70 mg/dL with typical symptoms such as giddiness, distress, fatigue and delirium.

Fatigue and reduced energy levels: The instant non availability of glucose in the blood for energy production, resulting in dip in the energy levels and fatigue.

Muscle wasting: Since the fat reserves and amino acids are getting utilized for energy production, there will be a general loss of muscle mass and impairment of the growth.

Unhealthy weight loss: The loss of fat and muscle mass leads to weight loss and emaciation.

Dehydration and reduced body secretions: Since there is loss of fluids from the body because of ketosis, a state of chronic dehydration is accomplished. This yields in reduction in mucus secretion, dry eyes and compromised mucus production in the tear glands, salivary glands, sinuses, airways, and gastrointestinal tract.

Loss of sodium: Surplus of ketone in the blood leads to fluid loss and excretion of the sodium ions (Na+) from the body. This might lead to muscle exhaustion, cramps and lassitude.

Weakened immune system: By increased fluid loss and degradation, vitamin C loss from the body is raised. Adding to this, the chronically dehydrated condition leads to weakened immune system and vulnerability to infections.

Constipation: Dietary fiber is the necessary component of carbohydrate food that is known to prevent recto-colon cancer and assist in digestion. The absence of dietary fiber can cause the constipation.

Mood swing: The dietary carbohydrate exclusion causes the brain to stop regulating serotonin hormone. Low serotonin supply causes the depression and mood swing.

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