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Aswan Dam
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For the older Aswan Dam built downstream in 1902, see Aswan Low Dam.
Aswan High Dam
The Aswan High Dam as seen from space
Location of the Aswan Dam in Egypt
Official name
Aswan High Dam
Location
Aswan, Egypt
Coordinates
23°58′14″N 32°52′40″E / 23.97056°N 32.87778°E / 23.97056; 32.87778Coordinates: 23°58′14″N 32°52′40″E / 23.97056°N 32.87778°E / 23.97056; 32.87778
Construction began
1960
Opening date
1970
Dam and spillways
Type of dam
Embankment
Impounds
River Nile
Height
111 m (364 ft)
Length
3,830 m (12,570 ft)
Width (base)
980 m (3,220 ft)
Spillway capacity
11,000 m3/s (390,000 cu ft/s)
Reservoir
Creates
Lake Nasser
Total capacity
132 km3 (107,000,000 acre·ft)
Surface area
5,250 km2 (2,030 sq mi)
Maximum length
550 km (340 mi)
Maximum width
35 km (22 mi)
Maximum water depth
180 m (590 ft)
Normal elevation
183 m (600 ft)
Power Station
Commission date
1967–1971
Turbines
12×175 MW (235,000 hp) Francis-type
Installed capacity
2,100 MW (2,800,000 hp)
Annual generation
10,042 GWh (2004)[1]
The Aswan Dam, or more specifically since the 1960s, the Aswan High Dam, is an embankment dam built across the Nile in Aswan, Egypt, between 1960 and 1970. Its significance largely eclipsed the previous Aswan Low Dam initially completed in 1902 downstream. Based on the success of the Low Dam, then at its maximum utilization, construction of the High Dam became a key objective of the government following the Egyptian Revolution of 1952; with its ability to control flooding better, provide increased water storage for irrigation and generate hydroelectricity the dam was seen as pivotal to Egypt's planned industrialization. Like the earlier implementation, the High Dam has had a significant effect on the economy and culture of Egypt.
Before the High Dam was built, even with the old dam in place, the annual flooding of the Nile during late summer had continued to pass largely unimpeded down the valley from its East African drainage basin. These floods brought high water with natural nutrients and minerals that annually enriched the fertile soil along its floodplain and delta; this predictability had made the Nile valley ideal for farming since ancient times. Since this natural flooding varied however, high-water years could destroy the whole crop, while low-water years could create widespread drought and associated famine. Both these events had continued to occur periodically. As Egypt's population grew and technology increased, both a desire and the ability developed to completely control the flooding, and thus both protect and support farmland and its economically important cotton crop. With the greatly increased reservoir storage provided by the High Aswan Dam, the floods could be controlled and the water could be stored for later release over multiple years.
Contents
[hide]
1 Construction history
1.1 Aswan Low Dam, 1898–1902
1.2 Aswan High Dam prelude, 1954–1959
1.3 Construction and filling, 1960–1976
2 Specifications
3 Irrigation scheme
4 Effects
4.1 Drought protection, agricultural production and employment
4.2 Electricity production
4.3 Resettlement
4.4 Archaeological sites
4.5 Loss of sediments
4.6 Waterlogging and increase in soil salinity
4.7 Health
4.8 Other effects
5 See also
6 References
7 External links
Construction history[edit]
The earliest recorded attempt to build a dam near Aswan was in the 11th century, when the Arab polymath and engineer Ibn al-Haytham (known as Alhazen in the West) was summoned to Egypt by the Fatimid Caliph, Al-Hakim bi-Amr Allah, to regulate the flooding of the Nile, a task requiring an early attempt at an Aswan Dam.[2] His field work convinced him of the impracticality of this scheme.[3]
Aswan Low Dam, 1898–1902[edit]
Main article: Aswan Low Dam
The British began construction of the first dam across the Nile in 1898. Construction lasted until 1902, and the dam was opened on 10 December 1902. The project was designed by Sir William Willcocks and involved several eminent engineers, including Sir Benjamin Baker and Sir John Aird, whose firm, John Aird & Co., was the main contractor.[4][5]
Aswan High Dam prelude, 1954–1959[edit]
In 1912, the Greek-Egyptian engineer Adrian Daninos began to develop the plan of the new Aswan Dam. Although the Low Dam was almost overtopped in 1946, the government of King Farouk showed no interest in Daninos's plans. Instead the Nile Valley Plan by the British hydrologist Harold Edwin Hurst to store water in Sudan and Ethiopia, where evaporation is much lower, was favored. The Egyptian position changed completely with the overthrow of the monarchy, led by the Free Officers Movement including Gamal Abdel Nasser. The Free Officers were convinced that the Nile Waters had to be stored in Egypt for political reasons, and within two months, the plan of Daninos was accepted.[6] Initially, both the United States and the USSR were interested in helping the development of the dam, but this movement happened in the midst of the Cold War, as well as of growing intra-Arab rivalries.
In 1955, Nasser was trying to portray himself as the leader of Arab nationalism, in opposition to the traditional monarchies, especially the Hashemite Kingdom of Iraq following its signing of the 1955 Baghdad Pact. At that time the U.S. feared that communism would spread to the Middle East, and it saw Nasser as a natural leader of an anticommunist procapitalist Arab League. America and Britain offered to help finance construction of the High Dam, with a loan of $270 million, in return for Nasser's leadership in resolving the Arab-Israeli conflict. While opposed both to communism, capitalism, and imperialism, Nasser presented himself as a tactical neutralist, and sought to work with both the U.S. and the USSR for Egyptian and Arab benefit.[7] After a particularly criticized raid by Israel against Egyptian forces in Gaza in 1955, Nasser realized that he could not legitimately portray himself as the leader of pan-Arab nationalism if he could not defend his country militarily against Israel. In addition to his development plans, he looked to quickly modernize his military, and he turned first to the U.S.
Egyptian President Nasser and Russian leader Nikita Khrushchev at the ceremony to divert the Nile during the construction of the Aswan High Dam on 14 May 1964. At this occasion Khrushchev called it "the eighth wonder of the world".
The American Secretary of State John Foster Dulles and the American President Dwight Eisenhower told Nasser that the U.S. would supply him with weapons only if they were used for defensive purposes and accompanied by American military personnel for supervision and training. Nasser did not accept these conditions, but then he looked to the USSR for support. Although Dulles believed that Nasser was only bluffing and that the USSR would not aid Nasser, he was wrong— the USSR promised Nasser a quantity of arms in exchange for a deferred payment of Egyptian grain and cotton. On 27 September 1955, Nasser announced an arms deal, with Czechoslovakia acting as a middleman for the Soviet support.[8] Instead of attacking Nasser for turning to the Soviets, Dulles sought to improve relations with him. This explains the later offer of December 1955, in which the U.S. and Britain pledged $56 and $14 million respectively towards the construction of the dam.[9]
Gamal Abdel Nasser observing the construction of the dam, 1963
Though the Czech arms deal actually increased the American willingness to invest at Aswan, Great Britain cited the deal as a reason for reversing its promise of funds. What angered Dulles much more was Nasser's diplomatic recognition of China, which was in direct conflict with Dulles's policy of containment.[10] There are several other reasons why the U.S. decided to withdraw its offer of funding. Dulles believed that the USSR would not fulfill its commitment to help the Egyptians. He was also irritated by Nasser's neutrality and attempts to play both sides of the Cold War. At the time, other western allies in the Middle East, including Turkey and Iraq, were irritated and jealous that Egypt, a persistently neutral country, was being offered so much aid.[11]
In June 1956, the Soviets offered Nasser $1.12 billion at 2% interest for the construction of the dam. On 19 July the U.S. State Department announced that American financial assistance for the High Dam was "not feasible in present circumstances."[9]
On 26 July 1956, with wide Egyptian acclaim, Nasser announced the nationalization of the Suez Canal as well as fair compensation for the former owners. Nasser planned on the revenues generated by the canal helping to fund construction of the High Dam. When the Suez War broke out, the United Kingdom, France, and Israel seized the canal and the Sinai, but pressure from the U.S. and the USSR at the United Nations and elsewhere forced them to withdraw.
In 1958, the USSR went ahead in providing support for the High Dam project.
A view from the vantage point in the middle of High Dam towards the monument of Arab-Soviet Friendship (Lotus Flower) by architects Piotr Pavlov, Juri Omeltchenko and sculptor Nikolay Vechkanov
In the 1950s, archaeologists began raising concerns that several major historical sites, including the famous temple of Abu Simbel were about to be under water. A rescue operation began in 1960 under UNESCO (for details see below under Effects).
Construction and filling, 1960–1976[edit]
A central pylon of the monument to Arab-Soviet Friendship. The memorial commemorates the completion of the Aswan High Dam. The coat of arms of the Soviet Union is on the left and the coat of arms of Egypt is on the right.
The Soviets also provided technicians and heavy machinery. The enormous rock and clay dam was designed by the Soviet Hydroproject Institute along with some Egyptian engineers. 25,000 Egyptian engineers and workers contributed to the construction of the dams.
On the Egyptian side, the project was led by Osman Ahmed Osman's Arab Contractors. The relatively young Osman underbid his only competitor by one-half.[12]
1960: Start of construction on 9 January[13]
1964: First dam construction stage completed, reservoir started filling
1970: The High Dam, as-Sad al-'Aali, completed on 21 July[14]
1976: Reservoir reached capacity
Specifications[edit]
The Aswan High Dam is 3,830 metres (12,570 ft) long, 980 m (3,220 ft) wide at the base, 40 m (130 ft) wide at the crest and 111 m (364 ft) tall. It contains 43,000,000 cubic metres (56,000,000 cu yd) of material. At maximum, 11,000 cubic metres per second (390,000 cu ft/s) of water can pass through the dam. There are further emergency spillways for an extra 5,000 cubic metres per second (180,000 cu ft/s), and the Toshka Canal links the reservoir to the Toshka Depression. The reservoir, named Lake Nasser, is 550 km (340 mi) long and 35 km (22 mi) at its widest, with a surface area of 5,250 square kilometres (2,030 sq mi). It holds 132 cubic kilometres (1.73×1011 cu yd) of water.
A panorama of the Aswan Dam
Irrigation scheme[edit]
See also: Water resources management in modern Egypt
Green irrigated land along the Nile amidst the desert
Water balances
Main irrigation systems (schematically)
Due to the absence of appreciable rainfall, Egypt's agriculture depends entirely on irrigation. With irrigation, two crops per year can be produced, except for sugar cane which has a growing period of almost one year.
The high dam at Aswan releases, on average, 55 cubic kilometres (45,000,000 acre·ft) water per year, of which some 46 cubic kilometres (37,000,000 acre·ft) are diverted into the irrigation canals.
In the Nile valley and delta, almost 33,600 square kilometres (13,000 sq mi) benefit from these waters producing on average 1.8 crops per year. The annual crop consumptive use of water is about 38 cubic kilometres (31,000,000 acre·ft). Hence, the overall irrigation efficiency is 38/46 = 0.82 or 82%. This is a relatively-high irrigation efficiency. The field irrigation efficiencies are much less, but the losses are reused downstream. This continuous reuse accounts for the high overall efficiency.
The following table shows that the equal distribution of irrigation water over the branch canals taking off from the one main irrigation canal, the Mansuriya Canal near Giza, leaves much to be desired:[15]
Branch canal
Water delivery in m3/feddan *
Kafret Nasser 4700
Beni Magdul 3500
El Mansuria 3300
El Hammami upstream 2800
El Hammami downstream 1800
El Shimi 1200
* Period 1 March to 31 July. 1 feddan is 0.42 ha or about 1 acre.
* Data from the Egyptian Water Use Management Project (EWUP)[16]
The salt concentration of the water in the Aswan reservoir is about 0.25 kilograms per cubic metre (0.42 lb/cu yd), a very low salinity level. At an annual inflow of 55 cubic kilometres (45,000,000 acre·ft), the annual salt influx reaches 14 million tons. The average salt concentration of the drainage water evacuated into the sea and the coastal lakes is 2.7 kilograms per cubic metre (4.6 lb/cu yd).[17] At an annual discharge of 10 cubic kilometres (2.4 cu mi) (not counting the 2 kilograms per cubic metre [3.4 lb/cu yd] of salt intrusion from the sea and the lakes, see figure "Water balances"), the annual salt export reaches 27 million ton. In 1995, the output of salt was higher than the influx, and Egypt's agricultural lands were desalinizing. Part of this could be due to the large number of subsurface drainage projects executed in the last decades to control the water table and soil salinity.[18]
Drainage through subsurface drains and drainage channels is essential to prevent a deterioration of crop yields from waterlogging and soil salinization caused by irrigation. By 2003, more than 20,000 square kilometres (7,700 sq mi) have been equipped with a subsurface drainage system and approximately 7.2 square kilometres (2.8 sq mi) of water is drained annually from areas with these systems. The total investment cost in agricultural drainage over 27 years from 1973 to 2002 was about $3.1 billion covering the cost of design, construction, maintenance, research and training. During this period 11 large-scale projects were implemented with financial support from World Bank and other donors[19]
Effects[edit]
The High Dam has resulted in protection from floods and droughts, an increase in agricultural production and employment, electricity production, and improved navigation that also benefits tourism. Conversely, the dam flooded a large area, causing the relocation of over 100,000 people. Many archaeological sites were submerged while others were relocated. The dam is blamed for coastline erosion, soil salinity, and health problems.
The assessment of the costs and benefits of the dam remains controversial decades after its completion. According to one estimate, the annual economic benefit of the High Dam immediately after its completion was E£255 million, $587 million using the exchange rate in 1970 of $2.30 per E£1): £140 million from agricultural production, £100 million from hydroelectric generation, £10 million from flood protection, and £5 million from improved navigation. At the time of its construction, total cost, including unspecified "subsidiary projects" and the extension of electric power lines, amounted to £450 million. Not taking into account the negative environmental and social effects of the dam, its costs are thus estimated to have been recovered within only two years.[20] One observer notes: "The impacts of the Aswan High Dam (...) have been overwhelmingly positive. Although the Dam has contributed to some environmental problems, these have proved to be significantly less severe than was generally expected, or currently believed by many people."[21] Another observer disagreed and he recommended that the dam should be torn down. Tearing it down would cost only a fraction of the funds required for "continually combating the dam's consequential damage" and 500,000 hectares of fertile land could be reclaimed from the layers of mud on the bed of the drained reservoir.[22]
Periodic floods and droughts have affected Egypt since ancient times. The dam mitigated the effects of floods, such as those in 1964, 1973, and 1988. Navigation along the river has been improved, both upstream and downstream of the dam. Sailing along the Nile is a favorite tourism activity, which is mainly done during the winter when the natural flow of the Nile would have been too low to allow navigation of cruise ships.[clarification needed] A new fishing industry has been created around Lake Nasser, though it is struggling due to its distance from any significant markets. The annual production was about 35 000 tons in the mid-1990s. Factories for the fishing industry and packaging have been set up near the Lake.[23]
Drought protection, agricultural production and employment[edit]
The Egyptian countryside benefited from the Aswan High Dam through improved irrigation as well as electrification, as shown here south of Luxor.
The dams also protected Egypt from the droughts in 1972–73 and 1983–87 that devastated East and West Africa. The High Dam allowed Egypt to reclaim about 2.0 million feddan (840,000 hectares) in the Nile Delta and along the Nile Valley, increasing the country's irrigated area by a third. The increase was brought about both by irrigating what used to be desert and by bringing under cultivation of 385,000 ha that were previously used as flood retention basins.[24] About half a million families were settled on these new lands. In particular the area under rice and sugar cane cultivation increased. In addition, about 1 million feddan (420,000 hectares), mostly in Upper Egypt, were converted from flood irrigation with only one crop per year to perennial irrigation allowing two or more crops per year. On other previously irrigated land, yields increased because water could be made available at critical low-flow periods. For example, wheat yields in Egypt tripled between 1952 and 1991 and better availability of water contributed to this increase. Most of the 32 km3 of freshwater, or almost 40 percent of the average flow of the Nile that were previously lost to the sea every year could be put to beneficial use. While about 10 km3 of the water saved is lost due to evaporation in Lake Nasser, the amount of water available for irrigation still increased by 22 km3.[23] Other estimates put evaporation from Lake Nasser at between 10 and 16 cubic km per year.[25]
Electricity production[edit]
Power plant of the Aswan High Dam, with the dam itself in the background.
The dam powers twelve generators each rated at 175 megawatts (235,000 hp), with a total of 2.1 gigawatts (2,800,000 hp). Power generation began in 1967. When the High Dam first reached peak output it produced around half of Egypt's production of electric power (about 15 percent by 1998), and it gave most Egyptian villages the use of electricity for the first time. The High Dam has also improved the efficiency and the extension of the Old Aswan Hydropower stations by regulating upstream flows.[23]
Resettlement[edit]
A picture of the old Wadi Halfa town that was flooded by Lake Nasser.
Lake Nasser flooded much of lower Nubia and 100,000 to 120,000 people were resettled in Sudan and Egypt.[26]
View of New Wadi Halfa, a settlement created on the shore of Lake Nasser to house part of the resettled population from the Old Wadi Halfa town.
In Sudan, 50,000 to 70,000 Sudanese Nubians were moved from the old town of Wadi Halfa and its surrounding villages. Some were moved to a newly created settlement on the shore of Lake Nasser called New Wadi Halfa, and some were resettled approximately 700 kilometres south to the semi-arid Butana plain near the town of Khashm el-Girba up the Atbara River. The climate there had a regular rainy season as opposed to their previous desert habitat in which virtually no rain fell. The government developed an irrigation project, called the New Halfa Agricultural Development Scheme to grow cotton, grains, sugar cane and other crops. The Nubians were resettled in twenty five planned villages that included schools, medical facilities, and other services, including piped water and some electrification.
In Egypt, the majority of the 50,000 Nubians were moved three to ten kilometers from the Nile near Kom Ombo, 45 kilometers downstream from Aswan in what was called “New Nubia”. Housing and facilities were built for 47 village units whose relationship to each other approximated that in Old Nubia. Irrigated land was provided to grow mainly sugar cane.[27][28]
Archaeological sites[edit]
The statue of Ramses the Great at the Great Temple of Abu Simbel is reassembled after having been moved in 1967 to save it from being flooded.
22 monuments and architectural complexes that were threatened by flooding from Lake Nasser, including the Abu Simbel temples, were preserved by moving them to the shores of the lake under the UNESCO Nubia Campaign.[29] Also moved were Philae, Kalabsha and Amada.[23]
These monuments were granted to countries that helped with the works:
The Debod temple to Madrid
The Temple of Dendur to the Metropolitan Museum of Art of New York
The Temple of Taffeh to the Rijksmuseum van Oudheden of Leiden
The Temple of Ellesyia to the Museo Egizio of Turin
These items were removed to the garden area of the Sudan National Museum of Khartoum:[30]
The temple of Ramses II at Aksha
The temple of Hatshepsut at Buhen
The temple of Khnum at Kumma
The tomb of the Nubian prince Djehuti-hotep at Debeira
The temples of Dedwen and Sesostris III at Semna
The granite columns from the Faras Cathedral
A part of the paintings of the Faras Cathedral; the other part is in the National Museum of Warsaw.
The remaining archaeological sites, including the Buhen fort or the cemetery of Fadrus have been flooded by Lake Nasser.
Loss of sediments[edit]
Lake Nasser behind the Aswan dam displaced more than 100,000 people and traps significant amounts of sediment.
Before the construction of the High Dam, the Nile deposited sediments of various particle size – consisting of fine sand, silt and clay – on fields in Upper Egypt through its annual flood, contributing to soil fertility. However, the nutrient value of the sediment has often been overestimated. 88 percent of the sediment was carried to the sea before the construction of the High Dam. The nutrient value added to the land by the sediment was only 6,000 tons of potash, 7,000 tons of phosphorus pentoxide and 17,000 tons of nitrogen. These amounts are insignificant compared to what is needed to reach the yields achieved today in Egypt's irrigation.[31] Also, the annual spread of sediment due to the Nile floods occurred along the banks of the Nile. Areas far from the river which never received the Nile floods before are now being irrigated.[32]
The trapping of sediment by the dam has also increased coastline erosion surrounding the Nile Delta. The coastline erodes an estimated 125–175 m (410–574 ft) per year.[33]
Waterlogging and increase in soil salinity[edit]
Before the construction of the High Dam, groundwater levels in the Nile Valley fluctuated 8–9 m per year with the water level of the Nile. During summer when evaporation was highest, the groundwater level was too deep to allow salts dissolved in the water to be pulled to the surface through capillary action. With the disappearance of the annual flood and heavy year-round irrigation, groundwater levels remained high with little fluctuation leading to waterlogging. Soil salinity also increased because the distance between the surface and the groundwater table was small enough (1–2 m depending on soil conditions and temperature) to allow water to be pulled up by evaporation so that the relatively small concentrations of salt in the groundwater accumulated on the soil surface over the years. Since most of the farmland did not have proper subsurface drainage to lower the groundwater table, salinization gradually affected crop yields.[24] Drainage through sub-surface drains and drainage channels is essential to prevent a deterioration of crop yields from soil salinization and waterlogging. By 2003, more than 2.0 million have been equipped with a subsurface drainage system at a cost from 1973 to 2002 of about $3.1 billion.[34]
Health[edit]
Skin vesicles: a symptom of schistosomiasis. A more common symptom is blood in the urine.
Contrary to many predictions made prior to the Aswan High Dam construction and publications that followed, that the prevalence of bilharzia (schistosomiasis) would increase, it did not.[35] This assumption did not take into account the extent of perennial irrigation that was already present throughout Egypt decades before the high dam closure. By the 1950s only a small proportion of Upper Egypt had not been converted from basin (low transmission) to perennial (high transmission) irrigation. Expansion of perennial irrigation systems in Egypt did not depend on the high dam. In fact, within 15 years of the high dam closure there was solid evidence that biharzia was declining in Upper Egypt. S. haematobium has since disappeared altogether.[36] Suggested reasons for this include improvements in irrigation practice. In the Nile Delta, schistosomaisis had been highly endemic, with prevalence in the villages 50% or higher for almost a century before. This was a consequence of the conversion of the Delta to perennial irrigation to grow long staple cotton by the British. This has changed. Large scale treatment programmes in the 1990s using single dose oral medication contributed greatly to reducing the prevalence and severity of S. mansoni in the Delta.
Other effects[edit]
Sediment deposited in the reservoir is lowering the water storage capacity of Lake Nasser. The reservoir storage capacity is 162 km3, including 31 km3 dead storage at the bottom of the lake below 147 m above sea level, 90 km3 live storage, and 41 km3 of storage for high flood waters above 175m above sea level. The annual sediment load of the Nile is about 134 million tons. This means that the dead storage volume would be filled up after 300–500 years if the sediment accumulated at the same rate throughout the area of the lake. Obviously sediment accumulates much faster at the upper reaches of the lake, where sedimentation has already affected the live storage zone.[31]
Before the construction of the High Dam, the 50,000 km of irrigation and drainage canals in Egypt had to be dredged regularly to remove sediments. After construction of the dam, aquatic weeds grew much faster in the clearer water, helped by fertilizer residues. The total length of the infested waterways was about 27,000 km in the mid-1990s. Weeds have been gradually brought under control by manual, mechanical and biological methods.[23]
The catch of sardines in the Mediterranean off the Egyptian coast declined after the Aswan Dam was completed, but the exact reasons for the decline are still disputed.
Mediterranean fishing and brackish water lake fishery declined after the dam was finished because nutrients that flowed down the Nile to the Mediterranean were trapped behind the dam. For example, the sardine catch off the Egyptian coast declined from 18,000 tons in 1962 to a mere 460 tons in 1968, but then gradually recovered to 8,590 tons in 1992. A scientific article in the mid-1990s noted that "the mismatch between low primary productivity and relatively high levels of fish production in the region still presents a puzzle to scientists."[37]
A concern before the construction of the High Dam had been the potential drop in river-bed level downstream of the Dam as the result of erosion caused by the flow of sediment-free water. Estimates by various national and international experts put this drop at between 2 and 10 meters. However, the actual drop has been measured at 0.3–0.7 meters, much less than expected.[23]
The red-brick construction industry, which consisted of hundreds of factories that used Nile sediment deposits along the river, has also been negatively affected. Deprived of sediment, they started using the older alluvium of otherwise arable land taking out of production up to 120 square kilometers annually, with an estimated 1,000 square kilometers destroyed by 1984 when the government prohibited, “with only modest success,” further excavation.[38] According to one source, bricks are now being made from new techniques which use a sand-clay mixture and it has been argued that the mud-based brick industry would have suffered even if the dam had not been built.[32]
Because of the lower turbidity of the water sunlight penetrates deeper in the Nile water. Because of this and the increased presence of nutrients from fertilizers in the water, more algae grow in the Nile. This in turn increases the costs of drinking water treatment. Apparently few experts had expected that water quality in the Nile would actually decrease because of the High Dam.[24]
See also[edit]
Egypt portal
Water portal
Renewable energy portal
Energy in Egypt
Egyptian Public Works
List of conventional hydroelectric power stations
List of largest dams
List of power stations in Egypt
Water politics in the Nile Basin
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Jump up ^ Reis, Michael (1999), Who is who in Ancient Egypt, p.48 ISBN 0-415-15448-0
^ Jump up to: a b Abu Zeid, M.A. (September 1989). "Environmental impacts of the High Dam". Water Resources Development. 5 (3): 156.
^ Jump up to: a b Biswas, Asit K.; Tortajada, Cecilia (March 2004), Hydropolitics and Impacts of the High Aswan Dam, Mexico: Third World Centre for Water Management
Jump up ^ Schwartz, Maurice L., ed. (2005). Encyclopedia of coastal science. Dordrecht: Springer. p. 358. ISBN 1-4020-1903-3.
Jump up ^ Ministry of Water Resources and Irrigation, Egyptian Public Authority for Drainage Projects, Drainage Research Institute, 2006: The National Drainage and Drainage Water Reuse Programs, Egypt, Local Actions at the 4th World Water Forum, March 2, 2007. Retrieved April 28, 2010.
Jump up ^ Miller. F. DeWolfe et al. Schistosomiasis in Rural Egypt. 1978. United States Environment Protection Agency. EPA – 600/1-78-070.
Jump up ^ Baraket, R. Epidemiology of Schistosomiasis in Egypt: Travel through Time: Review. Journal of Advanced Research (2013) 4, 425–432
Jump up ^ El-Sayed, Sayed; van Dijken, Gert L. (1995), The southeastern Mediterranean ecosystem revisited: Thirty years after the construction of the Aswan High Dam
Jump up ^ Scudder, Thayer (2003), The Aswan High Dam Case (PDF), p. 11
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Carbohydrate
From Wikipedia, the free encyclopedia
This is the latest accepted revision, reviewed on 9 October 2017.
Jump to: navigation, search
Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage. It has a formula of C12H22O11.
A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water); in other words, with the empirical formula Cm(H2O)n (where m could be different from n).[1] This formula holds true for monosaccharides. Some exceptions exist; for example, deoxyribose, a sugar component of DNA,[2] has the empirical formula C5H10O4.[3] Carbohydrates are technically hydrates of carbon;[4] structurally it is more accurate to view them as polyhydroxy aldehydes and ketones.[5]
The term is most common in biochemistry, where it is a synonym of 'saccharide', a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest (lower molecular weight) carbohydrates, are commonly referred to as sugars.[6] The word saccharide comes from the Greek word σάκχαρον (sákkharon), meaning "sugar". While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, grape sugar is the monosaccharide glucose, cane sugar is the disaccharide sucrose, and milk sugar is the disaccharide lactose.
Carbohydrates perform numerous roles in living organisms. Polysaccharides serve for the storage of energy (e.g. starch and glycogen) and as structural components (e.g. cellulose in plants and chitin in arthropods). The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g. ATP, FAD and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.[7]
In food science and in many informal contexts, the term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch (such as cereals, bread and pasta) or simple carbohydrates, such as sugar (found in candy, jams, and desserts).
Often in lists of nutritional information, such as the USDA National Nutrient Database, the term "carbohydrate" (or "carbohydrate by difference") is used for everything other than water, protein, fat, ash, and ethanol.[8] This will include chemical compounds such as acetic or lactic acid, which are not normally considered carbohydrates. It also includes dietary fiber which is a carbohydrate but which does not contribute much in the way of food energy (calories), even though it is often included in the calculation of total food energy just as though it were a sugar.
Carbohydrates are found in a wide variety of foods. The important sources are cereals (wheat, maize, rice), potatoes, sugarcane, fruits, table sugar (sucrose), bread, milk, etc. Starch and sugar are the important carbohydrates in our diet. Starch is abundant in potatoes, maize, rice and other cereals. Sugar appears in our diet mainly as sucrose (table sugar), which is added to drinks and many prepared foods such as jam, biscuits and cakes, and glucose and fructose which occur naturally in many fruits and some vegetables.
Glycogen is a carbohydrate found in the liver and muscles (as animal source). Cellulose in the cell wall of all plant tissue is a carbohydrate. It is important in our diet as fibre which helps to maintain a healthy digestive system.[9]
Contents
[hide]
1 Structure
2 Division
3 Monosaccharides
3.1 Classification of monosaccharides
3.2 Ring-straight chain isomerism
3.3 Use in living organisms
4 Disaccharides
5 Nutrition
5.1 Classification
6 Metabolism
6.1 Catabolism
7 Carbohydrate chemistry
8 See also
9 References
10 Sources
11 External links
Structure[edit]
Formerly the name "carbohydrate" was used in chemistry for any compound with the formula Cm (H2O)n. Following this definition, some chemists considered formaldehyde (CH2O) to be the simplest carbohydrate,[10] while others claimed that title for glycolaldehyde.[11] Today, the term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons and includes many biological carbohydrates which deviate from this formula. For example, while the above representative formulas would seem to capture the commonly known carbohydrates, ubiquitous and abundant carbohydrates often deviate from this. For example, carbohydrates often display chemical groups such as: N-acetyl (e.g. chitin), sulphate (e.g. glycosaminoglycans), carboxylic acid (e.g. sialic acid) and deoxy modifications (e.g. fucose and sialic acid).
Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. A typical monosaccharide has the structure H–(CHOH)x(C=O)–(CHOH)y–H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. Examples of monosaccharides are glucose, fructose, and glyceraldehydes. However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g. uronic acids and deoxy-sugars such as fucose) and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g. formaldehyde CH2O and inositol (CH2O)6).[12]
The open-chain form of a monosaccharide often coexists with a closed ring form where the aldehyde/ketone carbonyl group carbon (C=O) and hydroxyl group (–OH) react forming a hemiacetal with a new C–O–C bridge.
Monosaccharides can be linked together into what are called polysaccharides (or oligosaccharides) in a large variety of ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose, a component of DNA, is a modified version of ribose; chitin is composed of repeating units of N-acetyl glucosamine, a nitrogen-containing form of glucose.
Division[edit]
Carbohydrates are polyhydroxy aldehydes, ketones, alcohols, acids, their simple derivatives and their polymers having linkages of the acetal type. They may be classified according to their degree of polymerization and may be divided initially into three principal groups, namely sugars, oligosaccharides and polysaccharides[13]
The major dietary carbohydrates
Class (DP*)
Subgroup
Components
Sugars (1–2)
Monosaccharides Glucose, galactose, fructose, xylose
Disaccharides Sucrose, lactose, maltose, trehalose
Polyols Sorbitol, mannitol
Oligosaccharides (3–9)
Malto-oligosaccharides Maltodextrins
Other oligosaccharides Raffinose, stachyose, fructo-oligosaccharides
Polysaccharides (>9)
Starch Amylose, amylopectin, modified starches
Non-starch polysaccharides Cellulose, hemicellulose, pectins, hydrocolloids
DP * = Degree of polymerization
Monosaccharides[edit]
Main article: Monosaccharide
D-glucose is an aldohexose with the formula (C·H2O)6. The red atoms highlight the aldehyde group and the blue atoms highlight the asymmetric center furthest from the aldehyde; because this -OH is on the right of the Fischer projection, this is a D sugar.
Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. They are aldehydes or ketones with two or more hydroxyl groups. The general chemical formula of an unmodified monosaccharide is (C•H2O)n, literally a "carbon hydrate". Monosaccharides are important fuel molecules as well as building blocks for nucleic acids. The smallest monosaccharides, for which n=3, are dihydroxyacetone and D- and L-glyceraldehydes.
Classification of monosaccharides[edit]
The α and β anomers of glucose. Note the position of the hydroxyl group (red or green) on the anomeric carbon relative to the CH2OH group bound to carbon 5: they either have identical absolute configurations (R,R or S,S) (α), or opposite absolute configurations (R,S or S,R) (β).[14]
Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group, the number of carbon atoms it contains, and its chiral handedness. If the carbonyl group is an aldehyde, the monosaccharide is an aldose; if the carbonyl group is a ketone, the monosaccharide is a ketose. Monosaccharides with three carbon atoms are called trioses, those with four are called tetroses, five are called pentoses, six are hexoses, and so on.[15] These two systems of classification are often combined. For example, glucose is an aldohexose (a six-carbon aldehyde), ribose is an aldopentose (a five-carbon aldehyde), and fructose is a ketohexose (a six-carbon ketone).
Each carbon atom bearing a hydroxyl group (-OH), with the exception of the first and last carbons, are asymmetric, making them stereo centers with two possible configurations each (R or S). Because of this asymmetry, a number of isomers may exist for any given monosaccharide formula. Using Le Bel-van't Hoff rule, the aldohexose D-glucose, for example, has the formula (C·H2O)6, of which four of its six carbons atoms are stereogenic, making D-glucose one of 24=16 possible stereoisomers. In the case of glyceraldehydes, an aldotriose, there is one pair of possible stereoisomers, which are enantiomers and epimers. 1, 3-dihydroxyacetone, the ketose corresponding to the aldose glyceraldehydes, is a symmetric molecule with no stereo centers. The assignment of D or L is made according to the orientation of the asymmetric carbon furthest from the carbonyl group: in a standard Fischer projection if the hydroxyl group is on the right the molecule is a D sugar, otherwise it is an L sugar. The "D-" and "L-" prefixes should not be confused with "d-" or "l-", which indicate the direction that the sugar rotates plane polarized light. This usage of "d-" and "l-" is no longer followed in carbohydrate chemistry.[16]
Ring-straight chain isomerism[edit]
Glucose can exist in both a straight-chain and ring form.
The aldehyde or ketone group of a straight-chain monosaccharide will react reversibly with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal, forming a heterocyclic ring with an oxygen bridge between two carbon atoms. Rings with five and six atoms are called furanose and pyranose forms, respectively, and exist in equilibrium with the straight-chain form.[17]
During the conversion from straight-chain form to the cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon, becomes a stereogenic center with two possible configurations: The oxygen atom may take a position either above or below the plane of the ring. The resulting possible pair of stereoisomers is called anomers. In the α anomer, the -OH substituent on the anomeric carbon rests on the opposite side (trans) of the ring from the CH2OH side branch. The alternative form, in which the CH2OH substituent and the anomeric hydroxyl are on the same side (cis) of the plane of the ring, is called the β anomer.
Use in living organisms[edit]
Monosaccharides are the major source of fuel for metabolism, being used both as an energy source (glucose being the most important in nature) and in biosynthesis. When monosaccharides are not immediately needed by many cells they are often converted to more space-efficient forms, often polysaccharides. In many animals, including humans, this storage form is glycogen, especially in liver and muscle cells. In plants, starch is used for the same purpose. The most abundant carbohydrate, cellulose, is a structural component of the cell wall of plants and many forms of algae. Ribose is a component of RNA. Deoxyribose is a component of DNA. Lyxose is a component of lyxoflavin found in the human heart.[18] Ribulose and xylulose occur in the pentose phosphate pathway. Galactose, a component of milk sugar lactose, is found in galactolipids in plant cell membranes and in glycoproteins in many tissues. Mannose occurs in human metabolism, especially in the glycosylation of certain proteins. Fructose, or fruit sugar, is found in many plants and in humans, it is metabolized in the liver, absorbed directly into the intestines during digestion, and found in semen. Trehalose, a major sugar of insects, is rapidly hydrolyzed into two glucose molecules to support continuous flight.
Disaccharides[edit]
Sucrose, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).
Main article: Disaccharide
Two joined monosaccharides are called a disaccharide and these are the simplest polysaccharides. Examples include sucrose and lactose. They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C12H22O11. Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable.
Sucrose, pictured to the right, is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants. It is composed of one D-glucose molecule and one D-fructose molecule. The systematic name for sucrose, O-α-D-glucopyranosyl-(1→2)-D-fructofuranoside, indicates four things:
Its monosaccharides: glucose and fructose
Their ring types: glucose is a pyranose and fructose is a furanose
How they are linked together: the oxygen on carbon number 1 (C1) of α-D-glucose is linked to the C2 of D-fructose.
The -oside suffix indicates that the anomeric carbon of both monosaccharides participates in the glycosidic bond.
Lactose, a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in mammalian milk. The systematic name for lactose is O-β-D-galactopyranosyl-(1→4)-D-glucopyranose. Other notable disaccharides include maltose (two D-glucoses linked α-1,4) and cellulobiose (two D-glucoses linked β-1,4). Disaccharides can be classified into two types: reducing and non-reducing disaccharides. If the functional group is present in bonding with another sugar unit, it is called a reducing disaccharide or biose.
Nutrition[edit]
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Grain products: rich sources of carbohydrates
Carbohydrate consumed in food yields 3.87 calories of energy per gram for simple sugars,[19] and 3.57 to 4.12 calories per gram for complex carbohydrate in most other foods.[20] Relatively high levels of carbohydrate are associated with processed foods or refined foods made from plants, including sweets, cookies and candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit products, pastas and breakfast cereals. Lower amounts of carbohydrate are usually associated with unrefined foods, including beans, tubers, rice, and unrefined fruit.[21] Animal-based foods generally have the lowest carbohydrate levels, although milk does contain a high proportion of lactose.
Carbohydrates are a common source of energy in living organisms; however, no carbohydrate is an essential nutrient in humans.[22] Humans are able to obtain all of their energy requirement from protein and fats, though the potential for some negative health effects of extreme carbohydrate restriction remains, as the issue has not been studied extensively yet.[22] However, in the case of dietary fiber – indigestible carbohydrates which are not a source of energy – inadequate intake can lead to significant increases in mortality.[23]
Following a diet consisting of very low amounts of daily carbohydrate for several days will usually result in higher levels of blood ketone bodies than an isocaloric diet with similar protein content.[24] This relatively high level of ketone bodies is commonly known as ketosis and is very often confused with the potentially fatal condition often seen in type 1 diabetics known as diabetic ketoacidosis. Somebody suffering ketoacidosis will have much higher levels of blood ketone bodies along with high blood sugar, dehydration and electrolyte imbalance.
Long-chain fatty acids cannot cross the blood–brain barrier, but the liver can break these down to produce ketones. However, the medium-chain fatty acids octanoic and heptanoic acids can cross the barrier and be used by the brain, which normally relies upon glucose for its energy.[25][26][27] Gluconeogenesis allows humans to synthesize some glucose from specific amino acids: from the glycerol backbone in triglycerides and in some cases from fatty acids.
Organisms typically cannot metabolize all types of carbohydrate to yield energy. Glucose is a nearly universal and accessible source of energy. Many organisms also have the ability to metabolize other monosaccharides and disaccharides but glucose is often metabolized first. In Escherichia coli, for example, the lac operon will express enzymes for the digestion of lactose when it is present, but if both lactose and glucose are present the lac operon is repressed, resulting in the glucose being used first (see: Diauxie). Polysaccharides are also common sources of energy. Many organisms can easily break down starches into glucose; most organisms, however, cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose. Even though these complex carbohydrates are not very digestible, they represent an important dietary element for humans, called dietary fiber. Fiber enhances digestion, among other benefits.[28]
Based on the effects on risk of heart disease and obesity in otherwise healthy middle-aged adults,[29] the Institute of Medicine recommends that American and Canadian adults get between 45–65% of dietary energy from whole-grain carbohydrates.[30] The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).[31]
Classification[edit]
Nutritionists often refer to carbohydrates as either simple or complex. However, the exact distinction between these groups can be ambiguous. The term complex carbohydrate was first used in the U.S. Senate Select Committee on Nutrition and Human Needs publication Dietary Goals for the United States (1977) where it was intended to distinguish sugars from other carbohydrates (which were perceived to be nutritionally superior).[32] However, the report put "fruit, vegetables and whole-grains" in the complex carbohydrate column, despite the fact that these may contain sugars as well as polysaccharides. This confusion persists as today some nutritionists use the term complex carbohydrate to refer to any sort of digestible saccharide present in a whole food, where fiber, vitamins and minerals are also found (as opposed to processed carbohydrates, which provide energy but few other nutrients). The standard usage, however, is to classify carbohydrates chemically: simple if they are sugars (monosaccharides and disaccharides) and complex if they are polysaccharides (or oligosaccharides).[33]
In any case, the simple vs. complex chemical distinction has little value for determining the nutritional quality of carbohydrates.[33] Some simple carbohydrates (e.g. fructose) raise blood glucose slowly, while some complex carbohydrates (starches), especially if processed, raise blood sugar rapidly. The speed of digestion is determined by a variety of factors including which other nutrients are consumed with the carbohydrate, how the food is prepared, individual differences in metabolism, and the chemistry of the carbohydrate.[34]
The USDA's Dietary Guidelines for Americans 2010 call for moderate- to high-carbohydrate consumption from a balanced diet that includes six one-ounce servings of grain foods each day, at least half from whole grain sources and the rest from enriched.[35]
The glycemic index (GI) and glycemic load concepts have been developed to characterize food behavior during human digestion. They rank carbohydrate-rich foods based on the rapidity and magnitude of their effect on blood glucose levels. Glycemic index is a measure of how quickly food glucose is absorbed, while glycemic load is a measure of the total absorbable glucose in foods. The insulin index is a similar, more recent classification method that ranks foods based on their effects on blood insulin levels, which are caused by glucose (or starch) and some amino acids in food.
Metabolism[edit]
Main article: Carbohydrate metabolism
Carbohydrate metabolism denotes the various biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates in living organisms.
The most important carbohydrate is glucose, a simple sugar (monosaccharide) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of a wide variety of metabolic pathways across species: plants synthesize carbohydrates from carbon dioxide and water by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids. Plant components are consumed by animals and fungi, and used as fuel for cellular respiration. Oxidation of one gram of carbohydrate yields approximately 4 kcal of energy, while the oxidation of one gram of lipids yields about 9 kcal. Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP.[36] Organisms capable of aerobic respiration metabolize glucose and oxygen to release energy with carbon dioxide and water as byproducts.
Catabolism[edit]
Catabolism is the metabolic reaction which cells undergo to extract energy. There are two major metabolic pathways of monosaccharide catabolism: glycolysis and the citric acid cycle.
In glycolysis, oligo/polysaccharides are cleaved first to smaller monosaccharides by enzymes called glycoside hydrolases. The monosaccharide units can then enter into monosaccharide catabolism. In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present.
Carbohydrate chemistry[edit]
Carbohydrate chemistry is a large and economically important branch of organic chemistry. Some of the main organic reactions that involve carbohydrates are:
Carbohydrate acetalisation
Cyanohydrin reaction
Lobry de Bruyn–van Ekenstein transformation
Amadori rearrangement
Nef reaction
Wohl degradation
Koenigs–Knorr reaction
Carbohydrate digestion
See also[edit]
Bioplastic
Fermentation
Gluconeogenesis
Glycobiology
Glycoinformatics
Glycolipid
Glycome
Glycomics
Glycoprotein
Glycosyl
Low-carbohydrate diet
Macromolecule
No-carbohydrate diet
Nutrition
Pentose phosphate pathway
Photosynthesis
Resistant starch
Saccharic acid
Carbohydrate NMR
References[edit]
Jump up ^ Western Kentucky University (May 29, 2013). "WKU BIO 113 Carbohydrates". wku.edu.
Jump up ^ Eldra Pearl Solomon; Linda R. Berg; Diana W. Martin (2004). Biology. Cengage Learning. p. 52. ISBN 978-0534278281 – via google.books.com.
Jump up ^ National Institute of Standards and Technology (2011). "Material Measurement Library D-erythro-Pentose, 2-deoxy-". nist.gov.
Jump up ^ Long Island University (May 29, 2013). "The Chemistry of Carbohydrates" (PDF). brooklyn.liu.edu.
Jump up ^ Purdue University (May 29, 2013). "Carbohydrates: The Monosaccharides". purdue.edu.
Jump up ^ Flitsch, Sabine L.; Ulijn, Rein V (2003). "Sugars tied to the spot". Nature. 421 (6920): 219–20. Bibcode:2003Natur.421..219F. PMID 12529622. doi:10.1038/421219a.
Jump up ^ Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. pp. 52–59. ISBN 0-13-981176-1.
Jump up ^ USDA National Nutrient Database, 2015, p. 13
Jump up ^ USDA National Nutrient Database, 2015, p. 14
Jump up ^ John Merle Coulter, Charler Reid Barnes, Henry Chandler Cowles (1930), A Textbook of Botany for Colleges and Universities"
Jump up ^ Carl A. Burtis, Edward R. Ashwood, Norbert W. Tietz (2000), Tietz fundamentals of clinical chemistry
Jump up ^ Matthews, C. E.; K. E. Van Holde; K. G. Ahern (1999) Biochemistry. 3rd edition. Benjamin Cummings. ISBN 0-8053-3066-6
Jump up ^ "Carbohydrates in human nutrition – Chapter 1 – The role of carbohydrates in nutrition". Food and Agriculture Organization of the United Nations. FAO.
Jump up ^ Carolyn R Bertozzi. "Structural Basis of Glycan Diversity – Essentials of Glycobiology – NCBI Bookshelf". nih.gov.
Jump up ^ Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6.
Jump up ^ Pigman, Ward; Horton, D. (1972). "Chapter 1: Stereochemistry of the Monosaccharides". In Pigman and Horton. The Carbohydrates: Chemistry and Biochemistry Vol 1A (2nd ed.). San Diego: Academic Press. pp. 1–67.
Jump up ^ Pigman, Ward; Anet, E.F.L.J. (1972). "Chapter 4: Mutarotations and Actions of Acids and Bases". In Pigman and Horton. The Carbohydrates: Chemistry and Biochemistry Vol 1A (2nd ed.). San Diego: Academic Press. pp. 165–194.
Jump up ^ "lyxoflavin". Merriam-Webster.
Jump up ^ "Show Foods". usda.gov.
Jump up ^ "CALCULATION OF THE ENERGY CONTENT OF FOODS – ENERGY CONVERSION FACTORS". fao.org.
Jump up ^ "Carbohydrate reference list" (PDF). www.diabetes.org.uk. Retrieved October 30, 2016.
^ Jump up to: a b Westman, EC (2002). "Is dietary carbohydrate essential for human nutrition?". The American Journal of Clinical Nutrition. 75 (5): 951–3; author reply 953–4. PMID 11976176.
Jump up ^ Park, Y; Subar, AF; Hollenbeck, A; Schatzkin, A (2011). "Dietary fiber intake and mortality in the NIH-AARP diet and health study". Archives of Internal Medicine. 171 (12): 1061–8. PMC 3513325  . PMID 21321288. doi:10.1001/archinternmed.2011.18.
Jump up ^ "Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets" (PDF). nutrition.org.
Jump up ^ Douglas Ebert. "Energy Contribution of Octanoate to Intact Rat Brain Metabolism Measured by 13C Nuclear Magnetic Resonance Spectroscopy". jneurosci.org.
Jump up ^ "Heptanoate as a neural fuel: energetic and neurotransmitter precursors in normal and glucose transporter I-deficient (G1D) brain". Journal of Cerebral Blood Flow. 33: 175–182. doi:10.1038/jcbfm.2012.151.
Jump up ^ "Integration of Metabolism". medbio.info.
Jump up ^ Pichon, L; Huneau, JF; Fromentin, G; Tomé, D (2006). "A high-protein, high-fat, carbohydrate-free diet reduces energy intake, hepatic lipogenesis, and adiposity in rats". The Journal of Nutrition. 136 (5): 1256–60. PMID 16614413.
Jump up ^ Tighe, P; Duthie, G; Vaughan, N; Brittenden, J; Simpson, WG; Duthie, S; Mutch, W; Wahle, K; Horgan, G; Thies, F. (2010). "Effect of increased consumption of whole-grain foods on blood pressure and other cardiovascular risk markers in healthy middle-aged persons: a randomized, controlled trial". The American Journal of Clinical Nutrition. 92 (4): 733–40. PMID 20685951. doi:10.3945/ajcn.2010.29417.
Jump up ^ Food and Nutrition Board (2002/2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington, D.C.: The National Academies Press. Page 769. ISBN 0-309-08537-3.
Jump up ^ Joint WHO/FAO expert consultation (2003). [1] (PDF). Geneva: World Health Organization. pp. 55–56. ISBN 92-4-120916-X.
Jump up ^ Joint WHO/FAO expert consultation (1998), Carbohydrates in human nutrition, chapter 1. ISBN 92-5-104114-8.
^ Jump up to: a b "Carbohydrates". The Nutrition Source. Harvard School of Public Health. Retrieved April 3, 2013.
Jump up ^ Jenkins, David; Alexandra L. Jenkins; Thomas M.S. Woleve; Lilian H. Thompson; A. Venkat Rao (February 1986). "Simple and Complex Carbohydrates". Nutrition Reviews. 44 (2): 44–49. doi:10.1111/j.1753-4887.1986.tb07585.x.
Jump up ^ DHHS and USDA, Dietary Guidelines for Americans 2010.
Jump up ^ Energetics of Cellular Respiration (Glucose Metabolism)
Sources[edit]
"Compolition of foods raw, processed, prepared" (PDF). www.ars.usda.giv. September 2015. Retrieved October 30, 2016.
External links[edit]
Wikimedia Commons has media related to Carbohydrates.
Wikiquote has quotations related to: Carbohydrate
Carbohydrates, including interactive models and animations (Requires MDL Chime)
IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN): Carbohydrate Nomenclature
Carbohydrates detailed
Carbohydrates and Glycosylation – The Virtual Library of Biochemistry, Molecular Biology and Cell Biology
Functional Glycomics Gateway, a collaboration between the Consortium for Functional Glycomics and Nature Publishing Group
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LCCN: sh85020080
GND: 4164517-0
NDL: 00572696
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values: Ածխաջուր – Armenian

values: कार्बोहाइड्रेट – Hindi

values:
https://is.wikipedia.org/wiki/Sykra
Sykra – Icelandic
is
is
interlanguage-link-target

values:
https://it.wikipedia.org/wiki/Glucidi
Glucidi – Italian
it
it
interlanguage-link-target

values: פחמימה – Hebrew

values: ಕಾರ್ಬೋಹೈಡ್ರೇಟುಗಳು – Kannada

values: ნახშირწყლები – Georgian

values: Көмірсулар – Kazakh

values: Көмүрсуулар (углеводдор) – Kyrgyz

values: ກະລູຊິດ – Lao

values: Јаглехидрат – Macedonian

values: കാർബോഹൈഡ്രേറ്റ് – Malayalam

values: ნოშქერწყარეფი – Mingrelian

values: ကာဘိုဟိုက်ဒရိတ် – Burmese

values: कार्बोहाइड्रेट – Nepali

values: शर्करा – Newari

values:
https://oc.wikipedia.org/wiki/Glucid
Glucid – Occitan
oc
oc
interlanguage-link-target

values: ଶ୍ୱେତସାର – Odia

values: ਕਾਰਬੋਹਾਈਡਰੇਟ – Punjabi

values: کاربوہائیڈریٹ – Western Punjabi

values: Угльоводы – Rusyn

values: Углеводы – Russian

values: කාබෝහයිඩ්‍රේට – Sinhala

values:
https://sk.wikipedia.org/wiki/Sacharid
Sacharid – Slovak
sk
sk
interlanguage-link-target

values: Угљени хидрат – Serbian

values:
https://sv.wikipedia.org/wiki/Kolhydrat
Kolhydrat – Swedish
sv
sv
interlanguage-link-target

values: கார்போவைதரேட்டு – Tamil

values: Күмерсулар – Tatar

values: పిండి పదార్థాలు – Telugu

values: คาร์โบไฮเดรต – Thai

values: Карбогидратҳо – Tajik

values: Углеводтар – Tuvinian

values: Вуглеводи – Ukrainian

values: کاربو ہائیڈریٹ – Urdu

values: קארבאהידראט – Yiddish

values: कार्बोहाइड्रेट – Doteli

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