Respiratory system

Respiration organs

s (or breathing organs) are used by most, or all, animals to exchange the gases necessar

y for their life function known as respiration. These organs come in many forms, some of them apparently having independently evolved:

• skin – some aquatic,or some amphibians (ex.frogs) or small terrestrial (some of the smallest spiders and mites, for example), animals can breathe simply by exchanging gas through the surface of their body
• gill – many aquatic, and a few smaller terrestrial, animals use gills to breathe. Even land animals can do this, as with isopods like the woodlice that probably can be found living under rocks in a yard. Gills are simply layers of tissue adapted specifically to gas exchange.
• book lung – Some spiders, scorpions, and other arthropods still use primitive book lungs, essentially gills adapted for land use, in their respiration. These are simply tissue with many wrinkles to increase their surface area.
• Labyrinth organ – A secondary breathing organ specific to the labyrinth fish, essentially an enclosed maze of tissue, evolved from a niche in their gill structure.
• Invertebrate trachea – tubes evolved by many arthropods, possibly from book lungs, which simply lead directly into their bodies through holes called spiracles, where their internal organs generally absorb their own air. These can be very primitive, as with some spiders, or more complex, ending with specialized air sacs, as with many insects.
• lung – The lung is made up of muscle tissues, the cells inside the lung which collect the oxygen in the air and pass it into the blood stream via veins and carbon dioxide passes out and that is breathing respiratory.
• diaphragm – a layer of muscular membrane located at the bottom of the thoracic cavity which in responsible in adjusting the volume of thoracic cavity

Respiratory system

Respiratory system
A complete, schematic view of the human respiratory system.
Latin	systema respiratorium

The respiratory system's function is to allow gas exchange to all parts of the body. The space between the alveoli and the capillaries, the anatomy or structure of the exchange system, and the precise physiological uses of the exchanged gases vary depending on the organism. In humans and other mammals, for example, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveolar region of the lungs.^[1]

Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants also includes anatomical features such as holes on the undersides of leaves known as stomata.

Anatomy in vertebrates

Mammals

For mammals, including humans, respiration is essential. In these organisms, the respiratory system can be subdivided into an upper respiratory tract and a lower respiratory tract based on anatomical features. The upper respiratory tract includes the nasal passages, pharynx and the larynx, while the lower buttt faces comprises the trachea, the primary bronchi and lungs. The respiratory system can also be divided into physiological, or functional, zones. These include the conducting zone (the region for gas transport from the outside atmosphere to just above the alveoli), the transitional zone, and the respiratory zone (the alveolar region where gas exchange occurs). (See also respiratory tract.)

Comparative anatomy and physiology

Horses

Horses are obligate nasal breathers. That is, they are different from many other mammals in that they do not have the option of breathing through their mouths and must take in air through their nose. (See also Respiratory system of the horse.)

Elephants

The elephant is the only animal known to have no pleural space. Rather, the parietal and visceral pleura are both composed of dense connective tissue and joined to each other via loose connective tissue. This lack of a pleural space, along with an unusually thick diaphragm, are thought to be evolutionary adaptations allowing the elephant to remain underwater for long periods of time while breathing through its trunk which emerges as a snorkel.

Birds

The respiratory system of birds differs significantly from that found in mammals, containing unique anatomical features such as air sacs. The lungs of birds also do not have the capacity to inflate as birds lack a diaphragm and a pleural cavity. Gas exchange in birds occurs between air capillaries and blood capillaries, rather than in alveoli. See Avian respiratory system for a detailed description of these and other. features.

Reptiles

The anatomical structure of the lungs is less complex in reptiles than in mammals, with reptiles lacking the very extensive airway tree structure found in mammalian lungs. Gas exchange in reptiles still occurs in alveoli, however. Reptiles do not possess a diaphragm. Thus, breathing occurs via a change in the volume of the body cavity which is controlled by contraction of intercostal muscles in all reptiles except turtles. In turtles, contraction of specific pairs of flank muscles governs inspiration or expiration.

See also reptiles for more detailed descriptions of the respiratory system in these animals.

Amphibians

Both the lungs and the skin serve as respiratory organs in amphibians. The skin of these animals is highly vascularized and moist, with moisture maintained via secretion of mucus from specialized cells. While the lungs are of primary importance to breathing control, the skin's unique properties aid rapid gas exchange when amphibians are submerged in oxygen-rich water.

Fish

In most fish the respiration takes place through gills. (See also aquatic respiration.) Lungfish, however, do possess one or two lungs. The labyrinth fish have developed a special organ that allows them to take advantage of the oxygen of the air, but is not a true lung.

Anatomy in invertebrates

Insects

Air enters the respiratory system of most insects through a series of external openings called spiracles. These external openings, which act as muscular valves in some insects, lead to the internal respiratory system, a densely-networked array of tubes called trachea. The tracheal system within an individual is composed of interconnecting transverse and longitudinal tracheae which maintain equivalent pressure throughout the system. These tracheae branch repeatedly, eventually forming tracheoles, which are blind-ended, water-filled compartments only one micrometer in diameter. It is at this level of the tracheoles that oxygen is delivered to the cells for respiration.

Insects were once believed to exchange gases with the environment continuously by the simple diffusion of gases into the tracheal system. More recently, however, large variation in insect ventilatory patterns have been documented and insect respiration appears to be highly variable. Some small insects do demonstrate continuous respiration and may lack muscular control of the spiracles. Others, however, utilize muscular contraction of the abdomen along with coordinated spiracle contraction and relaxation to generate cyclical gas exchange patterns. The most extreme form of these patterns is termed discontinuous gas exchange cycles (DGC).^[9]

Mollusks

Mollusks generally possess gills that allow exchange of oxygen from an aqueous environment into the circulatory system. These animals also possess a heart that pumps blood which contains hemocyanin as its oxygen-capturing molecule. Hence, this respiratory system is similar to that of vertebrate fish. Respiratory system of gastropods include gills or lung.

Physiology in mammals

For more detailed descriptions see also Respiratory physiology or Respiration.

Ventilation

Ventilation of the lungs is carried out by the muscles of respiration.

Control

Ventilation occurs under the control of the autonomic nervous system from parts of the brain stem, the medulla oblongata and the pons. This area of the brain forms the respiration regulatory center, a series of interconnected brain cells within the lower and middle brain stem which coordinate respiratory movements. The sections are the pneumotaxic center, the apneustic center, and the dorsal and ventral respiratory groups. This section is especially sensitive during infancy, and the neurons can be destroyed if the infant is dropped and/or shaken violently. The result can be death due to "shaken baby syndrome."

Inhalation

Inhalation is initiated by the diaphragm and supported by the external intercostal muscles. Normal resting respirations are 10 to 18 breaths per minute, with a time period of 2 seconds. During vigorous inhalation (at rates exceeding 35 breaths per minute), or in approaching respiratory failure, accessory muscles of respiration are recruited for support. These consist of sternocleidomastoid, platysma, and the scalene muscles of the neck.

Under normal conditions, the diaphragm is the primary driver of inhalation. When the diaphragm contracts, the ribcage expands and the contents of the abdomen are moved downward. This results in a larger thoracic volume and negative (suction) pressure (with respect to atmospheric pressure) inside the thorax. As the pressure in the chest falls, air moves into the conducting zone. Here, the air is filtered, warmed, and humidified as it flows to the lungs.

During forced inhalation, as when taking a deep breath, the external intercostal muscles and accessory muscles aid in further expanding the thoracic cavity.

Exhalation

Exhalation is generally a passive process; however, active or forced exhalation is achieved by the abdominal and the internal intercostal muscles. During this process air is forced or exhaled out.

The lungs have a natural elasticity: as they recoil from the stretch of inhalation, air flows back out until the pressures in the chest and the atmosphere reach equilibrium.

During forced exhalation, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles, generate abdominal and thoracic pressure, which forces air out of the lungs.

Circulation

The right side of the heart pumps blood from the right ventricle through the pulmonary semilunar valve into the pulmonary trunk. The trunk branches into right and left pulmonary arteries to the pulmonary blood vessels. The vessels generally accompany the airways and also undergo numerous branchings. Once the gas exchange process is complete in the pulmonary capillaries, blood is returned to the left side of the heart through four pulmonary veins, two from each side. The pulmonary circulation has a very low resistance, due to the short distance within the lungs, compared to the systemic circulation, and for this reason, all the pressures within the pulmonary blood vessels are normally low as compared to the pressure of the systemic circulation loop.

Gas exchange

The major function of the respiratory system is gas exchange between the external environment and an organism's circulatory system. In humans and mammals, this exchange facilitates oxygenation of the blood with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the circulation. As gas exchange occurs, the acid-base balance of the body is maintained as part of homeostasis. If proper ventilation is not maintained, two opposing conditions could occur: respiratory acidosis, a life threatening condition, and respiratory alkalosis.

Upon inhalation, gas exchange occurs at the alveoli, the tiny sacs which are the basic functional component of the lungs. The alveolar walls are extremely thin (approx. 0.2 micrometres). These walls are composed of a single layer of epithelial cells (type I and type II epithelial cells) in close proximity to the pulmonary capillaries which are composed of a single layer of endothelial cells. The close proximity of these two cell types allows permeability to gases and, hence, gas exchange. This whole mechanism of gas exchange is carried by the simple phenomenon of pressure difference. When the atmospheric pressure is low outside the air from lungs flow out. When the air pressure is low inside, then the vice versa.

Non-respiratory functions

Vocalization

The movement of gas through the larynx, pharynx and mouth allows humans to speak, or phonate. Vocalization, or singing, in birds occurs via the syrinx, an organ located at the base of the trachea. The vibration of air flowing across the larynx (vocal chords), in humans, and the syrinx, in birds, results in sound. Because of this, gas movement is extremely vital for communication purposes.

Temperature control

Panting in dogs and some other animals provides a means of controlling body temperature. This physiological response is used as a cooling mechanism.

Coughing and sneezing

Irritation of nerves within the nasal passages or airways, can induce coughing and sneezing. These responses cause air to be expelled forcefully from the trachea or nose, respectively. In this manner, irritants caught in the mucus which lines the respiratory tract are expelled or moved to the mouth where they can be swallowed.

Development in animals

Humans and mammals

The respiratory system lies dormant in the human fetus during pregnancy. At birth, the respiratory system becomes fully functional upon exposure to air, although some lung development and growth continues throughout childhood. Pre-term birth can lead to infants with under-developed lungs. These lungs show incomplete development of the alveolar type II cells, cells that produce surfactant. The lungs of pre-term infants may not function well because the lack of surfactant leads to increased surface tension within the alveoli. Thus, many alveoli collapse such that no gas exchange can occur within some or most regions of an infant's lungs, a condition termed respiratory distress syndrome. Basic scientific experiments, carried out using cells from chicken lungs, support the potential for using steroids as a means of furthering development of type II alveolar cells. In fact, once a pre-mature birth is threatened, every effort is made to delay the birth, and a series of steroid shots is frequently administered to the mother during this delay in an effort to promote lung growth.

Disease

Disorders of the respiratory system can be classified into four general areas:

• Obstructive conditions (e.g., emphysema, bronchitis, asthma attacks)
• Restrictive conditions (e.g., fibrosis, sarcoidosis, alveolar damage, pleural effusion)
• Vascular diseases (e.g., pulmonary edema, pulmonary embolism, pulmonary hypertension)
• Infectious, environmental and other "diseases" (e.g., pneumonia, tuberculosis, asbestosis, particulate pollutants): Coughing is of major importance, as it is the body's main method to remove dust, mucus, saliva, and other debris from the lungs. Inability to cough can lead to infection. Deep breathing exercises may help keep finer structures of the lungs clear from particulate matter, etc.

The respiratory tract is constantly exposed to microbes due to the extensive surface area, which is why the respiratory system includes many mechanisms to defend itself and prevent pathogens from entering the body.

Disorders of the respiratory system are usually treated internally by a pulmonologist.

Plants

Plants use carbon dioxide gas in the process of photosynthesis, and then exhale oxygen gas, a waste product of photosynthesis. However, plants also sometimes respire as humans do, taking in oxygen and producing carbon dioxide.

Plant respiration is limited by the process of diffusion. Plants take in carbon dioxide through holes on the undersides of their leaves known as stomata (sing:stoma). However, most plants require little air.^{[citation needed]} Most plants have relatively few living cells outside of their surface because air (which is required for metabolic content) can penetrate only skin deep. However, most plants are not involved in highly aerobic activities, and thus have no need of these living cells.

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digestive system in human

Definition of Digestion of Food:Process of transformation of food into their soluble substance into the blood is called Digetion Food. For the digestion human digestive system is very neccessary.

Digestive System:

Is the system that makes food absorbable into the body .The digestive tract (also known as the alimentary canal) is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. The major functions of the GI tract are ingestion, digestion, absorption, and defecation.

The digestive system is made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food (see figure).Organs that make up the digestive tract are the mouth, esophagus, stomach, small intestine, large intestine—also called the colon—rectum, and anus. Inside these hollow organs is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract.Two “solid” digestive organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes called ducts. The gallbladder stores the liver’s digestive juices until they are needed in the intestine. Parts of the nervous and circulatory systems also play major roles in the digestive system.

Why The Digestion Of Food So Important?
When you eat foods—such as bread, meat, and vegetables—they are not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.

Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.

Movement of Food Through the System:

The large, hollow organs of the digestive tract contain a layer of muscle that enables their walls to move. The movement of organ walls can propel food and liquid through the system and also can mix the contents within each organ. Food moves from one organ to the next through muscle action called peristalsis. Peristalsis looks like an ocean wave traveling through the muscle. The muscle of the organ contracts to create a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.

The first major muscle movement occurs when food or liquid is swallowed. Although you are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.

Swallowed food is pushed into the esophagus, which connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike muscle, called the lower esophageal sphincter, closing the passage between the two organs. As food approaches the closed sphincter, the sphincter relaxes and allows the food to pass through to the stomach.

The stomach has three mechanical tasks. First, it stores the swallowed food and liquid. To do this, the muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine.

Several factors affect emptying of the stomach, including the kind of food and the degree of muscle action of the emptying stomach and the small intestine. Carbohydrates, for example, spend the least amount of time in the stomach, while protein stays in the stomach longer, and fats the longest. As the food dissolves into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.

Finally, the digested nutrients are absorbed through the intestinal walls and transported throughout the body. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are pushed into the colon, where they remain until the feces are expelled by a bowel movement.
Production of Digestive Juices

The digestive glands that act first are in the mouth—the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules. An enzyme is a substance that speeds up chemical reactions in the body.

The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. A thick mucus layer coats the mucosa and helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.

After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food. One of these organs, the pancreas, produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine.

The second organ, the liver, produces yet another digestive juice—bile. Bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder, through the bile ducts, and into the intestine to mix with the fat in food. The bile acids dissolve fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.

Absorption and Transport of Nutrients:

This part of the process varies with different types of nutrients are Given below: Carbohydrates, Protein, Fats, Vitamins & Water and salt.

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Carbohydrates

Carbohydrates - Chemical Structure

Carbohydrates consist of the elements carbon (C), hydrogen (H) and oxygen (O) with a ratio of hydrogen twice that of carbon and oxygen. Carbohydrates include sugars, starches, cellulose and many other compounds found in living organisms. In their basic form, carbohydrates are simple sugars or monosaccharides. These simple sugars can combine with each other to form more complex carbohydrates. The combination of two simple sugars is a disaccharide. Carbohydrates consisting of two to ten simple sugars are called oligosaccharides, and those with a larger number are called polysaccharides.

Sugar and Cotton are Carbohydrates

Sugars

Sugars are white crystalline carbohydrates that are soluble in water and generally have a sweet taste.

Monosaccharides are simple sugars

Monosaccharide classifications based on the number of carbons

Number of Carbons	Category Name	Examples
4	Tetrose	Erythrose, Threose
5	Pentose	Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose
6	Hexose	Allose, Altrose, Fructose, Galactose, Glucose, Gulose, Idose, Mannose, Sorbose, Talose, Tagatose
7	Heptose	Sedoheptulose

Many saccharide structures differ only in the orientation of the hydroxyl groups (-OH). This slight structural difference makes a big difference in the biochemical properties, organoleptic properties (e.g., taste), and in the physical properties such as melting point and Specific Rotation (how polarized light is distorted). A chain-form monosaccharide that has a carbonyl group (C=O) on an end carbon forming an aldehyde group (-CHO) is classified as an aldose. When the carbonyl group is on an inner atom forming a ketone, it is classified as a ketose.

Tetroses

D-Erythrose	D-Threose

Pentoses

D-Ribose	D-Arabinose	D-Xylose	D-Lyxose

The ring form of ribose is a component of ribonucleic acid (RNA). Deoxyribose, which is missing an oxygen at position 2, is a component of deoxyribonucleic acid (DNA). In nucleic acids, the hydroxyl group attached to carbon number 1 is replaced with nucleotide bases.

Ribose	Deoxyribose

Hexoses

Hexoses, such as the ones illustrated here, have the molecular formula C₆H₁₂O₆. German chemist Emil Fischer (1852-1919) identified the stereoisomers for these aldohexoses in 1894. He received the 1902 Nobel Prize for chemistry for his work.

D-Allose	D-Altrose	D-Glucose	D-Mannose

D-Gulose	D-Idose	D-Galactose	D-Talose

Structures that have opposite configurations of a hydroxyl group at only one position, such as glucose and mannose, are called epimers. Glucose, also called dextrose, is the most widely distributed sugar in the plant and animal kingdoms and it is the sugar present in blood as "blood sugar". The chain form of glucose is a polyhydric aldehyde, meaning that it has multiple hydroxyl groups and an aldehyde group. Fructose, also called levulose or "fruit sugar", is shown here in the chain and ring forms. The relationship between the chain and the ring forms of the sugars is discussed below. Fructose and glucose are the main carbohydrate constituents of honey.

D-Tagatose (a ketose)	D-Fructose	Fructose	Galactose	Mannose

Heptoses

Sedoheptulose has the same structure as fructose, but it has one extra carbon.

D-Sedoheptulose

Chain and Ring forms

Many simple sugars can exist in a chain form or a ring form, as illustrated by the hexoses above. The ring form is favored in aqueous solutions, and the mechanism of ring formation is similar for most sugars. The glucose ring form is created when the oxygen on carbon number 5 links with the carbon comprising the carbonyl group (carbon number 1) and transfers its hydrogen to the carbonyl oxygen to create a hydroxyl group. The rearrangement produces alpha glucose when the hydroxyl group is on the opposite side of the -CH₂OH group, or beta glucose when the hydroxyl group is on the same side as the -CH₂OH group. Isomers, such as these, which differ only in their configuration about their carbonyl carbon atom are called anomers. The little D in the name derives from the fact that natural glucose is dextrorotary, i.e., it rotates polarized light to the right, but it now denotes a specific configuration. Monosaccharides forming a five-sided ring, like ribose, are called furanoses. Those forming six-sided rings, like glucose, are called pyranoses.

D-Glucose (an aldose)	α-D-Glucose	β-D-Glucose	Cyclation of Glucose

Stereochemistry

Saccharides with identical functional groups but with different spatial configurations have different chemical and biological properties. Stereochemisty is the study of the arrangement of atoms in three-dimensional space. Stereoisomers are compounds in which the atoms are linked in the same order but differ in their spatial arrangement. Compounds that are mirror images of each other but are not identical, comparable to left and right shoes, are called enantiomers. The following structures illustrate the difference between β-D-Glucose and β-L-Glucose. Identical molecules can be made to correspond to each other by flipping and rotating. However, enantiomers cannot be made to correspond to their mirror images by flipping and rotating. Glucose is sometimes illustrated as a "chair form" because it is a more accurate representation of the bond angles of the molecule. The "boat" form of glucose is unstable.

β-D-Glucose	β-L-Glucose	β-D-Glucose (chair form)
β-D-Glucose	β-L-Glucose	β-D-Glucose (boat form)

Sugar Alcohols, Amino Sugars, and Uronic Acids

Sugars may be modified by natural or laboratory processes into compounds that retain the basic configuration of saccharides, but have different functional groups. Sugar alcohols, also known as polyols, polyhydric alcohols, or polyalcohols, are the hydrogenated forms of the aldoses or ketoses. For example, glucitol, also known as sorbitol, has the same linear structure as the chain form of glucose, but the aldehyde (-CHO) group is replaced with a -CH₂OH group. Other common sugar alcohols include the monosaccharides erythritol and xylitol and the disaccharides lactitol and maltitol. Sugar alcohols have about half the calories of sugars and are frequently used in low-calorie or "sugar-free" products.

Xylitol, which has the hydroxyl groups oriented like xylose, is a very common ingredient in "sugar-free" candies and gums because it is approximately as sweet as sucrose, but contains 40% less food energy. Although this sugar alcohol appears to be safe for humans, xylitol in relatively small doses can cause seizures, liver failure, and death in dogs.

Amino sugars or aminosaccharides replace a hydroxyl group with an amino (-NH₂) group. Glucosamine is an amino sugar used to treat cartilage damage and reduce the pain and progression of arthritis.

Uronic acids have a carboxyl group (-COOH) on the carbon that is not part of the ring. Their names retain the root of the monosaccharides, but the -ose sugar suffix is changed to -uronic acid. For example, galacturonic acid has the same configuration as galactose, and the structure of glucuronic acid corresponds to glucose.

Glucitol or Sorbitol (a sugar alcohol)	Glucosamine (an amino sugar)	Glucuronic acid (a uronic acid)

Carbohydrates - Chemical Structure

Disaccharides consist of two simple sugars

Disaccharide descriptions and components

Disaccharide	Description	Component monosaccharides
sucrose	common table sugar	glucose 1α→2 fructose
maltose	product of starch hydrolysis	glucose 1α→4 glucose
trehalose	found in fungi	glucose 1α→1 glucose
lactose	main sugar in milk	galactose 1β→4 glucose
melibiose	found in legumes	galactose 1α→6 glucose

Sucrose	Lactose	Maltose

Sucrose, also called saccharose, is ordinary table sugar refined from sugar cane or sugar beets. It is the main ingredient in turbinado sugar, evaporated or dried cane juice, brown sugar, and confectioner's sugar. Lactose has a molecular structure consisting of galactose and glucose. It is of interest because it is associated with lactose intolerance which is the intestinal distress caused by a deficiency of lactase, an intestinal enzyme needed to absorb and digest lactose in milk. Undigested lactose ferments in the colon and causes abdominal pain, bloating, gas, and diarrhea. Yogurt does not cause these problems because lactose is consumed by the bacteria that transform milk into yogurt.

Maltose consists of two α-D-glucose molecules with the alpha bond at carbon 1 of one molecule attached to the oxygen at carbon 4 of the second molecule. This is called a 1α→4 glycosidic linkage. Trehalose has two α-D-glucose molecules connected through carbon number one in a 1α→1 linkage. Cellobiose is a disaccharide consisting of two β-D-glucose molecules that have a 1β→4 linkage as in cellulose. Cellobiose has no taste, whereas maltose and trehalose are about one-third as sweet as sucrose.

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Trisaccharides

Raffinose, also called melitose, is a trisaccharide that is widely found in legumes and cruciferous vegetables, including beans, peas, cabbage, brussels sprouts, and broccoli. It consists of galactose connected to sucrose via a 1α→6 glycosidic linkage. Humans cannot digest saccharides with this linkage and the saccharides are fermented in the large intestine by gas-producing bacteria. Tablets containing the enzyme alpha-galactosidase, such as Beano, are frequently used as digestive aids to prevent gas and bloating. The enzyme is derived from selected strains of the food grade fungus Aspergillus niger.

Raffinose

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Polysaccharides are polymers of simple sugars

Many polysaccharides, unlike sugars, are insoluble in water. Dietary fiber includes polysaccharides and oligosaccharides that are resistant to digestion and absorption in the human small intestine but which are completely or partially fermented by microorganisms in the large intestine. The polysaccharides described below play important roles in nutrition, biology, or food preparation.

Starch

Starch is the major form of stored carbohydrate in plants. Starch is composed of a mixture of two substances: amylose, an essentially linear polysaccharide, and amylopectin, a highly branched polysaccharide. Both forms of starch are polymers of α-D-Glucose. Natural starches contain 10-20% amylose and 80-90% amylopectin. Amylose forms a colloidal dispersion in hot water (which helps to thicken gravies) whereas amylopectin is completely insoluble.

• Amylose molecules consist typically of 200 to 20,000 glucose units which form a helix as a result of the bond angles between the glucose units.
  

  Amylose

  
  
• Amylopectin differs from amylose in being highly branched. Short side chains of about 30 glucose units are attached with 1α→6 linkages approximately every twenty to thirty glucose units along the chain. Amylopectin molecules may contain up to two million glucose units.

Amylopectin

The side branching chains are clustered together within the amylopectin molecule

Starches are transformed into many commercial products by hydrolysis using acids or enzymes as catalysts. Hydrolysis is a chemical reaction in which water is used to break long polysaccharide chains into smaller chains or into simple carbohydrates. The resulting products are assigned a Dextrose Equivalent (DE) value which is related to the degree of hydrolysis. A DE value of 100 corresponds to completely hydrolyzed starch, which is pure glucose (dextrose). Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch. Dextrins are mixtures of polymers of D-glucose units linked by 1α→4 or 1α→6 glycosidic bonds. Maltodextrin is partially hydrolyzed starch that is not sweet and has a DE value less than 20. Syrups, such as corn syrup made from corn starch, have DE values from 20 to 91. Commercial dextrose has DE values from 92 to 99. Corn syrup solids, which may be labeled as soluble corn fiber or resistant maltodextrin, are mildly sweet semi-crystalline or powdery amorphous products with DEs from 20 to 36 made by drying corn syrup in a vacuum or in spray driers. Resistant maltodextrin or soluble corn fiber are not broken down in the digestive system, but they are partially fermented by colonic bacteria thus providing only 2 Calories per gram instead of the 4 Calories per gram in corn syrup. High fructose corn syrup (HFCS), commonly used to sweeten soft drinks, is made by treating corn syrup with enzymes to convert a portion of the glucose into fructose. Commercial HFCS contains from 42% to 55% fructose, with the remaining percentage being mainly glucose. Modified starch is starch that has been changed by mechanical processes or chemical treatments to stabilize starch gels made with hot water. Without modification, gelled starch-water mixtures lose viscosity or become rubbery after a few hours. Hydrogenated glucose syrup (HGS) is produced by hydrolyzing starch, and then hydrogenating the resulting syrup to produce sugar alcohols like maltitol and sorbitol, along with hydrogenated oligo- and polysaccharides. Polydextrose (poly-D-glucose) is a synthetic, highly-branched polymer with many types of glycosidic linkages created by heating dextrose with an acid catalyst and purifying the resulting water-soluble polymer. Polydextrose is used as a bulking agent because it is tasteless and is similar to fiber in terms of its resistance to digestion. The name resistant starch is applied to dietary starch that is not degraded in the stomach and small intestine, but is fermented by microflora in the large intestine.

Relative sweetness of various carbohydrates

fructose	173
invert sugar*	120
HFCS (42% fructose)	120
sucrose	100
xylitol	100
tagatose	92
glucose	74
high-DE corn syrup	70
sorbitol	55
mannitol	50
trehalose	45
regular corn syrup	40
galactose	32
maltose	32
lactose	15

* invert sugar is a mixture of glucose and fructose found in fruits.

Glycogen

Glucose is stored as glycogen in animal tissues by the process of glycogenesis. When glucose cannot be stored as glycogen or used immediately for energy, it is converted to fat. Glycogen is a polymer of α-D-Glucose identical to amylopectin, but the branches in glycogen tend to be shorter (about 13 glucose units) and more frequent. The glucose chains are organized globularly like branches of a tree originating from a pair of molecules of glycogenin, a protein with a molecular weight of 38,000 that acts as a primer at the core of the structure. Glycogen is easily converted back to glucose to provide energy.

Glycogen

Dextran

Dextran is a polysaccharide similar to amylopectin, but the main chains are formed by 1α→6 glycosidic linkages and the side branches are attached by 1α→3 or 1α→4 linkages. Dextran is an oral bacterial product that adheres to the teeth, creating a film called plaque. It is also used commercially in confections, in lacquers, as food additives, and as plasma volume expanders.

Dextran

Inulin

Some plants store carbohydrates in the form of inulin as an alternative, or in addition, to starch. Inulins are present in many vegetables and fruits, including onions, leeks, garlic, bananas, asparagus, chicory, and Jerusalem artichokes. Inulins are polymers consisting of fructose units that typically have a terminal glucose. Oligofructose has the same structure as inulin, but the chains consist of 10 or fewer fructose units. Oligofructose has approximately 30 to 50 percent of the sweetness of table sugar. Inulin is less soluble than oligofructose and has a smooth creamy texture that provides a fat-like mouthfeel. Inulin and oligofructose are nondigestible by human intestinal enzymes, but they are totally fermented by colonic microflora. The short-chain fatty acids and lactate produced by fermentation contribute 1.5 kcal per gram of inulin or oligofructose. Inulin and oligofructose are used to replace fat or sugar and reduce the calories of foods like ice cream, dairy products, confections and baked goods.

Inulin n = approx. 35

Carbohydrates - Chemical Structure

Cellulose

Cellulose is a polymer of β-D-Glucose, which in contrast to starch, is oriented with -CH₂OH groups alternating above and below the plane of the cellulose molecule thus producing long, unbranched chains. The absence of side chains allows cellulose molecules to lie close together and form rigid structures. Cellulose is the major structural material of plants. Wood is largely cellulose, and cotton is almost pure cellulose. Cellulose can be hydrolyzed to its constituent glucose units by microorganisms that inhabit the digestive tract of termites and ruminants. Cellulose may be modified in the laboratory by treating it with nitric acid (HNO₃) to replace all the hydroxyl groups with nitrate groups (-ONO₂) to produce cellulose nitrate (nitrocellulose or guncotton) which is an explosive component of smokeless powder. Partially nitrated cellulose, known as pyroxylin, is used in the manufacture of collodion, plastics, lacquers, and nail polish.

Cellulose

Hemicellulose

The term "hemicellulose" is applied to the polysaccharide components of plant cell walls other than cellulose, or to polysaccharides in plant cell walls which are extractable by dilute alkaline solutions. Hemicelluloses comprise almost one-third of the carbohydrates in woody plant tissue. The chemical structure of hemicelluloses consists of long chains of a variety of pentoses, hexoses, and their corresponding uronic acids. Hemicelluloses may be found in fruit, plant stems, and grain hulls. Although hemicelluloses are not digestible, they can be fermented by yeasts and bacteria. The polysaccharides yielding pentoses on hydrolysis are called pentosans. Xylan is an example of a pentosan consisting of D-xylose units with 1β→4 linkages.

Xylan

Arabinoxylan

Arabinoxylans are polysaccharides found in the bran of grasses and grains such as wheat, rye, and barley. Arabinoxylans consist of a xylan backbone with L-arabinofuranose (L-arabinose in its 5-atom ring form) attached randomly by 1α→2 and/or 1α→3 linkages to the xylose units throughout the chain. Since xylose and arabinose are both pentoses, arabinoxylans are usually classified as pentosans. Arabinoxylans are important in the baking industry. The arabinose units bind water and produce viscous compounds that affect the consistency of dough, the retention of gas bubbles from fermentation in gluten-starch films, and the final texture of baked products.

Arabinoxylan

Chitin

Chitin is an unbranched polymer of N-Acetyl-D-glucosamine. It is found in fungi and is the principal component of arthropod and lower animal exoskeletons, e.g., insect, crab, and shrimp shells. It may be regarded as a derivative of cellulose, in which the hydroxyl groups of the second carbon of each glucose unit have been replaced with acetamido (-NH(C=O)CH₃) groups.

Chitin

Beta-Glucan

Beta-glucans consist of linear unbranched polysaccharides of β-D-Glucose like cellulose, but with one 1β→3 linkage for every three or four 1β→4 linkages. Beta-glucans form long cylindrical molecules containing up to about 250,000 glucose units. Beta-glucans occur in the bran of grains such as barley and oats, and they are recognized as being beneficial for reducing heart disease by lowering cholesterol and reducing the glycemic response. They are used comercially to modify food texture and as fat substitutes.

Beta-Glucan

Glycosaminoglycans

Glycosaminoglycans are found in the lubricating fluid of the joints and as components of cartilage, synovial fluid, vitreous humor, bone, and heart valves. Glycosaminoglycans are long unbranched polysaccharides containing repeating disaccharide units that contain either of two amino sugar compounds -- N-acetylgalactosamine or N-acetylglucosamine, and a uronic acid such as glucuronate (glucose where carbon six forms a carboxyl group). Glycosaminoglycans are negatively charged, highly viscous molecules sometimes called mucopolysaccharides. The physiologically most important glycosaminoglycans are hyaluronic acid, dermatan sulfate, chondroitin sulfate, heparin, heparan sulfate, and keratan sulfate. Chondroitin sulfate is composed of β-D-glucuronate linked to the third carbon of N-acetylgalactosamine-4-sulfate as illustrated here. Heparin is a complex mixture of linear polysaccharides that have anticoagulant properties and vary in the degree of sulfation of the saccharide units.

Chondroitin Sulfate	Heparin

Agar and Carrageenan

Agar (agar agar) is extracted from seaweed and is used in many foods as a gelling agent. Agar is a polymer of agarobiose, a disaccharide composed of D-galactose and 3,6-anhydro-L-galactose. Highly refined agar is used as a medium for culturing bacteria, cellular tissues, and for DNA fingerprinting. Agar is used as an ingredient in desserts in Japan and other Asian countries. The gels produced with agar have a crispier texture than the desserts made with animal gelatin.

Carrageenan is a generic term for several polysaccharides also extracted from seaweed. Carrageenan compounds differ from agar in that they have sulfate groups (-OSO₃^-) in place of some hydroxyl groups. Carrageenan is also used for thickening, suspending, and gelling food products.

Agarobiose is the repeating disaccharide unit in agar.

Alginic acid, Alginates

Alginate is extracted from seaweeds, such as giant kelp (Macrocystis pyrifera). The chemical constituents of alginate are random sequences of chains of β-D-mannuronic and α-L-guluronic acids attached with 1→4 linkages. Alginates are insoluble in water, but absorb water readily. They are useful as gelling and thickening agents. Alginates are used in the manufacture of textiles, paper, and cosmetics. The sodium salt of alginic acid, sodium alginate, is used in the food industry to increase viscosity and as an emulsifier. Alginates are found in food products such as ice cream and in slimming aids where they serve as appetite suppresants. In dentistry, alginates are used to make dental impressions.

Alginic acid

Galactomannan

Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups. The mannopyranose units are linked with 1β→4 linkages to which galactopyranose units are attached with 1α→6 linkages. Galactomannans are present in several vegetable gums that are used to increase the viscosity of food products. These are the approximate ratios of mannose to galactose for the following gums:

• Fenugreek gum, mannose:galactose 1:1
• Guar gum, mannose:galactose 2:1
• Tara gum, mannose:galactose 3:1
• Locust bean gum or Carob gum, mannose:galactose 4:1

Guar is a legume that has been traditionally cultivated as livestock feed. Guar gum is also known by the name cyamopsis tetragonoloba which is the Latin taxonomy for the guar bean or cluster bean. Guar gum is the ground endosperm of the seeds. Approximately 85% of guar gum is guaran, a water soluble polysaccharide consisting of linear chains of mannose with 1β→4 linkages to which galactose units are attached with 1α→6 linkages. The ratio of mannose to galactose is 2:1. Guar gum has five to eight times the thickening power of starch and has many uses in the pharmaceutical industry, as a food stabilizer, and as a source of dietary fiber.

Guaran is the principal polysaccharide in guar gum.

Pectin

Pectin is a polysaccharide that acts as a cementing material in the cell walls of all plant tissues. The white portion of the rind of lemons and oranges contains approximately 30% pectin. Pectin is the methylated ester of polygalacturonic acid, which consists of chains of 300 to 1000 galacturonic acid units joined with 1α→4 linkages. The Degree of Esterification (DE) affects the gelling properties of pectin. The structure shown here has three methyl ester forms (-COOCH₃) for every two carboxyl groups (-COOH), hence it is has a 60% degree of esterification, normally called a DE-60 pectin. Pectin is an important ingredient of fruit preserves, jellies, and jams.

Pectin is a polymer of α-Galacturonic acid with a variable number of methyl ester groups.

Xanthan Gum

Xanthan gum is a polysaccharide with a β-D-glucose backbone like cellulose, but every second glucose unit is attached to a trisaccharide consisting of mannose, glucuronic acid, and mannose. The mannose closest to the backbone has an acetic acid ester on carbon 6, and the mannose at the end of the trisaccharide is linked through carbons 6 and 4 to the second carbon of pyruvic acid. Xanthan Gum is produced by the bacterium Xanthomonas campestris, which is found on cruciferous vegetables such as cabbage and cauliflower. The negatively charged carboxyl groups on the side chains cause the molecules to form very viscous fluids when mixed with water. Xanthan gum is used as a thickener for sauces, to prevent ice crystal formation in ice cream, and as a low-calorie substitute for fat. Xanthan gum is frequently mixed with guar gum because the viscosity of the combination is greater than when either one is used alone.

The repeating unit of Xanthan Gum

Glucomannan

Glucomannan is a dietary fiber obtained from tubers of Amorphophallus konjac cultivated in Asia. Flour from the konjac tubers is used to make Japanese shirataki noodles, also called konnyaku noodles, which are very low in calories. Glucomannan is used as a hunger suppressant because it produces a feeling of fullness by creating very viscous solutions that retard absorption of the nutrients in food. One gram of this soluble polysaccharide can absorb up to 200 ml of water, so it is also used for absorbent articles such as disposable diapers and sanitary napkins. The polysaccharide consists of glucose (G) and mannose (M) in a proportion of 5:8 joined by 1β→4 linkages. The basic polymeric repeating unit has the pattern: GGMMGMMMMMGGM. Short side chains of 11-16 monosaccharides occur at intervals of 50-60 units of the main chain attached by 1β→3 linkages. Also, acetate groups on carbon 6 occur at every 9-19 units of the main chain. Hydrolysis of the acetate groups favors the formation of intermolecular hydrogen bonds that are responsible for the gelling action.

A portion (GGMM) of the glucomannan repeating unit.
The second glucose has an acetate group.

function and clasification

The main function is as a source of carbohydrates in food biokalori, besides that, also as a thickening or GMC in food technology as a stabilizer, sweetener (sucrose, glucose, fructose) and fuel, such as the glucose and starch, and as a constituent cell structure, such as cellulose and khitin. (Sudarmadji, 1996)

Carbohydrates have an important role in determining food characteristics such as taste, color and texture. While the function of carbohydrates in the body are:

1. Its main function as a source of energy (1 gram of carbohydrate produces 4 calories) for the needs of tissue cells of the body. Some of carbohydrates changed directly into energy for body activities, and partly in the form of glycogen stored in the liver and muscles. There are several body tissues such as the nervous system and red blood cells can only use the energy derived from carbohydrates alone.

2. Proteins to protect not burned as energy producers.

3. Body's need for energy is the first priority, when carbohydrate intake is insufficient for the body's energy needs and if there is not enough fat in the food or stored fat reserves in the body, it will replace the function of proteins as energy-producing carbohydrates. Thus the protein will leave its main function as a building material. If this situation continuous, then the state of energy and protein deficiency (KEP) can not be avoided anymore.

4. Helps metabolize fats and proteins, thereby preventing the occurrence of ketosis, and excessive protein breakdown.

5. In the liver function to detoxify toxic substances specific.

6. Several types of carbohydrates have a special function in the body. Lactose such as working to help the absorption of calcium. Ribose is an essential component in nucleic acids.

7. In addition some carbohydrate groups that can not be digested, contains fiber (dietary fiber) are useful for digestion, such as cellulose, pectin and lignin.

There are several classifications of carbohydrates, classification based on the body's ability to digest and classification based on a lot of sugar constituent. Based on the body's ability to digest carbohydrates, carbohydrates are classified into carbohydrates that can be digested and not digested. While classification based on the number of carbohydrates into sugar constituent monosaccharide, disaccharide, oligosaccharide and polysaccharide. While based on the complexity of late carbohydrates are divided into two simple kerbohidrat (Mono, Di, oligosaccharide) and complex carbohydrates (starch, Starch Non Polysacharide (NSP) and resistant starch).



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SUMBER KARBOHIDRAT: Asupan makanan dengan kandungan karbohidrat tinggi seperti roti tawar, mie dan nasi sebaiknya dibatasi. Jika berlebih, bisa memicu serangan jantung.

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