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8a. Carbon in Living Organisms

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Organic carbon is a crucial component and a source of energy stored in carbon bonds and used by all living beings. Organisms (called autotrophs) extract carbon from the air in the form of CO2 converting it into organic carbon and building nutrients. Using the sunlight’s energy plants and plankton absorb and combine CO2 and water to form sugar (CH2O) and oxygen: CO2 + H2O + energy = CH2O + O2. Glucose, fructose, and other sugars, through processes such as respiration, create fuel for further metabolic processes. Plants can break down the sugar to get the energy. Other organisms (called heterotrophs) cannot fix carbon and must obtain organic carbon by consuming other organisms.

In chemical reactions, also those involving carbon, matter releases or absorbs energy. For example, energy release in the form of heat or light happens when methane CH4 is combusted in the presence of oxygen O2 into carbon dioxide CO2 and water H2O (CH4 + 2O2 > CO2 + 2H2O + energy). Energy absorption happens for example, during electrolysis of water, when water H2O plus energy changes into hydrogen H2 and oxygen O2 (2H2O + energy > 2H2 + O2).

Animals (including people) can get energy from breaking down the plant or plankton sugar; they have to eat it first. Nutrition consumed by animals provides compound substances for further processing. Oxygen combines with sugar to release water, carbon dioxide, and energy: CH2O + O2 = CO2 + H2O + energy. Then, carbon (as CO2) returns to the atmosphere because plants and plankton die and decay, bacteria decompose dead organisms, or fire burns out plants. Such chemical reactions may explain why compost, a decomposed and recycled organic matter used as a fertilizer, releases heat during breaking down the organic materials.

We are all made of carbon (and of water as well). Carbon is second element (18% by mass) after oxygen (65% by mass) that makes human body. Human cells, which consist of 65-90% water, are apart of it composed of organic molecules containing carbon.

Brandon Hummel "Life Forms"

Brandon Hummel “Life Forms”

brandonhummel2

5 Graphite

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Carbon as graphite is the softest of natural substances. Natural graphite may be crystalline flake graphite that forms planes of cyclic, with atoms of carbon arranged in a honeycomb lattice, amorphous, and lump graphite. Natural graphite, mined and then refined, may contain up to 98% of carbon. It is opaque, black, and conducts electricity well so is used, for example in arc lamp electrodes. Natural and synthetic graphite is a good dry lubricant: despite being in the solid phase it reduces friction between surfaces that are sliding against each other. Graphite, which was earlier called black lead or plumbago has been used in steelmaking, brake linings, as a recyclable anode in batteries, as a lubricant in air compressors, railway track joints, ball bearings, for lining molds for cannonballs, and also in food industry. Graphite has been used for decorating pottery since the 4th millennium B.C. Synthetic graphite serves as a matrix in nuclear reactors. Carbon nanotubes reinforce plastics and thus many commercial articles.

Characteristics of Carbon

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The different forms of carbon include the hardest naturally occurring substance, diamond, and one of the softest substances, graphite. It also bonds with other atoms fairly easily and is also capable of forming covalent bonds with other atoms. This makes carbon able to make the majority of chemical compounds with almost ten million different compounds. Carbon has the highest sublimation point (transition from solid straight to gas [2]) of all the elements. It also has no melting point at atmospheric pressure because it has a triple point (the temperature and pressure at which the solid, liquid, and gas states coexist in equilibrium [3]) at 7820 degrees Fahrenheit. This means the sublimation point is at about 3900 Kelvin.

 

Carbon compounds form the basics of all life on Earth. The carbon-nitrogen cycle even provides some of the energy produced by the sun. There are many forms of carbon, and many varieties, however most of them are unreactive under normal conditions. It doesn’t react with sulfuric acid, hydrochloric acid, chlorine or any alkalis. Carbon resists all most all oxidizers at normal temperatures and pressures. At higher temperatures carbon with oxygen forms carbon oxides. Carbon can combine with some metals when there is a high temperature to form metallic carbides, which are used for making harder, tips for cutting tools and is also used for abrasives.

 

http://en.wikipedia.org/wiki/Carbon,

 

Carbon Dating

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Carbon is also useful in other places in science. Carbon can be used to date objects with a process called carbon dating. Carbon dating is one of the main methods used to understand the age of fossils and artifacts. It’s relatively simple. C-14 is a more rare type of carbon isotope. It is produced in the upper atmosphere when nitrogen-14 is altered through cosmic radiation. The carbon isotope created from this is called “radiocarbon” because it’s radioactive. This radioactive isotope is absorbed into the objects, and ground of the area it is near. After a period of time it will decay back into nitrogen-14. It takes about 5730 years for half of the sample of this radiocarbon to decay. The way carbon dating works is that scientists measure the amount of C-14 in whatever it is we want to know the age of. If the amount is half of what it should be then we know the sample is 5730 years old. If the sample has one fourth of the C-14 then it is 11,460 years old. After about 10 half-lives (around 50,000 years), the amount of radiocarbon left in any sample is too small to be measured. This technique is useful for dating anything that died less than 60,000 years ago.

 

http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/carbondating.htm,

November 7, 2012, 9:01 am

Applications

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All life depends on carbon to survive. Carbon is in food and wood, but it is also present in fossil fuel methane gas and oil. Crude oil is used to produce gasoline and kerosene, which we all use in our daily lives. Another form of carbon is in a polymer made by plants, which takes the form of cotton, linen, and hemp. Other forms of carbon are extremely varied. It forms alloys when combined with iron. It can be combined with clay to form ‘lead’ used in pencils. It can be used as a pigment, as a mold for glass manufacture, in dry batteries, and also can be used as a neutron moderator in nuclear reactors.

 

Charcoal is used as a drawing material and also for grilling and space heating. Diamonds are used in jewelry. Industrial diamonds are used in drilling, cutting and polishing tools for other metals and stones. Plastics are made from carbon fiber and other components.

By Fatima Chavez

By Fatima Chavez


 

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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Graphite (Production)

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There are three types of natural graphite: amorphous, flake, and vein or lump. Amorphous graphite is the most abundant type and also the lowest quality.  Amorphous is used for lower value graphite products and is the lowest priced graphite. Flake graphite is higher quality than amorphous and it occurs as plates that are crystallized in metamorphic rock. This type of graphite can be used for such things as flame retardant substances. Vein or lump graphite is the rarest and most valuable form of graphite.

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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Diamonds (Production)

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Only very small amounts of diamond ore are actual diamonds. Historically, diamonds were known to be found in alluvial deposits in south India. Diamond production only started in the 1870s after the discovery of the diamonds fields in South Africa. About 4.5 billion carats of diamonds have been mined since then.  About 20 percent of this has been mined in the last 5 years.  In the United States, diamonds have been found in Colorado, Arkansas, and Montana. In 2005, Russia produced about one-fifth of the global diamond output. Australia has the richest “diamaniferous pipe” with about 42 metric tons per year in production.

 

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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History

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Carbon has been known and used since ancient times. There are records of it in ancient recollections. However, it was not recognized as an element until much later. The name comes from the Latin word “carbo” which means, “Charcoal”. Carbon in its forms of charcoal, soot and coal has been used since prehistoric times. Carbon as diamond has also been known since ancient times. Soot, graphite, and diamonds are all forms of carbon. Harry Kroto discovered a fourth form, called buckminsterfullerene, a few years ago. The framework of C60 is close to what we see as a soccer ball with the pentagon shapes forming a spherical structure.

 

http://www.webelements.com/carbon/

November 1, 2012, 1:07 pm

Organometallic Compounds

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Organometallic compounds are defined as containing at least one carbon-metal bond. This bond can be either a direct carbon to metal bond or a complex metal bond. Compounds containing metal to hydrogen bonds containing nonmetallic elements bonded to carbon are sometimes included in organometallic compounds. Some characteristics of these compounds are low melting points, insolubility in water, toxicity, oxidizability, and high reactivity.

Lauren Arline-Metallurgy

Lauren Arline-Metallurgy


 

http://www.chemistryexplained.com/Ny-Pi/Organometallic-Compounds.html#b,

November 6, 2012, 1:42 pm

Inorganic Compounds

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Most often, compounds containing carbon, which are associated with minerals, or those that don’t contain hydrogen or fluorine are thought separate from classical organic compounds. However, this is not entirely true. There are also oxides of carbon, which are relatively simple. The most common of these is carbon dioxide. It is a minor component of the Earth’s atmosphere. When dissolved in water, carbon dioxide forms carbonic acid. Another common oxide is carbon monoxide. It is a colorless, odorless gas. With reactive metals, like tungsten, carbon forms carbides or acetylides. These compounds are alloys with high melting points. With an electronegativity of 2.5, carbon forms covalent bonds easiest. Some other forms of carbides are “covalent lattices”, like carborundum, which is a lot like diamond.

 

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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Organic Compounds

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Carbon has the ability to form very long chains of connecting carbon-to-carbon bonds. C-C bonds are very strong, and very stable. This property means that carbon can form thousands and thousands of different compounds. There are more known compounds containing carbon the amount of compounds of the other chemical elements combined (excluding hydrogen because almost all organic compounds contain hydrogen as well). The simplest form of an organic molecule formed by carbon compounds is the hydrocarbon. These molecules are made of hydrogen atoms bonded to chains of carbon atoms. The molecules have different properties based on the chain length and the side chains formed by the different molecules. Carbon also occurs in all known organic life. It is the basis for organic chemistry. When combined with hydrogen, it forms hydrocarbons, which are used as lubricants and solvents and refrigerants. It is also used to manufacture plastic and is used as fossil fuels.

 

When combined with oxygen and hydrogen, carbon can form compounds such as sugars, alcohols, and fats. When combined with nitrogen it forms alkaloids. With nitrogen and sulfur it forms antibiotics, amino acids, and rubber. When phosphorus is added to these other elements, carbon forms DNA and RNA and also ATP (the energy-transferring molecule in all living cells).

 

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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Carbon Cycle

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Carbon is part of the oceans, air, rocks, soil, and all other living things. It is always moving from place to place. Carbon moves from the air to plants. In the atmosphere, carbon is attached to oxygen in the form of carbon dioxide. With the process of photosynthesis, the plants use the carbon dioxide and sunlight to make food for it. Then the carbon moves from the plants to the animals. It moves to the animals when they eat the plants. Animals that eat other animals get carbon from the animals that eat the plants. When the plants and animals die, their bodies decay and bring the carbon into the ground. Some animals, buried deep underground, form fossil fuels after millions of years. Carbon also moves from living things into the atmosphere. Every time people exhale, carbon dioxide gas is released into the atmosphere. Carbon moves from fossil fuels to the atmosphere when the fuels are burned. When the fuels are burned, they return to the atmosphere as carbon dioxide gas once again.  Carbon dioxide is moved from the atmosphere to the oceans. The oceans and other bodies of water pick up carbon from the atmosphere when it rains and also through absorption.

 

http://www.windows2universe.org/earth/Water/co2_cycle.html,

November 6, 2012 2:16 pm

Carbon Essentials

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  • Name: Carbon
  • Symbol: C
  • Atomic number: 6
  • Atomic weight: 12.0107
  • Standard state: Solid
  • Group in the periodic table: 14
  • Period in the periodic table: 2
  • Block in the periodic table: p-block
  • Color: In graphite form, carbon is black. In diamond form, it is colorless
  • Classification: non-metallic

A new form, aside from the common graphite and diamond forms, of carbon called buckminsterfullerene or C60 was discovered. It is of high interest to scientists and is being researched in laboratories. Carbon is also present in the atmosphere as carbon dioxide and is also dissolved in all natural waters. It is bar of rocs as carbonates of calcium, magnesium and iron. Ninety-six percent of the atmosphere of Mars is carbon dioxide.

 

Hydrocarbons, another form of carbon bonds, are coal petroleum and natural gas. Carbon is unique among other elements because of the amount of bonds it is able to form with other elements. Organic chemistry is the study of carbon and its compounds. Silicon can take the place of carbon in forming many compounds, but it is not able to currently form stable compounds with long chains of silicon atoms.

 

http://www.webelements.com/carbon/

November 1, 2012, 1:07 pm

Isotopes

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Carbon Isotopes

Carbon has three naturally occurring isotopes (isotopes have in their nuclei equal numbers of protons but different numbers of neutrons), with 12C and 13C being stable; carbon 14C is a radioactive isotope decaying with a half-life of about 5,730 years (half-life tells time isotope falls to half of its original radioactivity).

Radiocarbon dating, invented in 1949 by Willard Libby (the 1960 Nobel Prize) is a 14C-based radiometric method of estimating the age of materials aged up to 58,000–62,000 years. Older samples contain too small number of remaining intrinsic 14C carbon. Carbon dating allows estimate the age of organic remains and artifacts, objects of cultural or historical value, if they contain carbon. Scientists collected wood of the same age (based on the tree ring analysis) to increase accuracy of the technique. They have also measured radiocarbon in stalactites and stalagmites (called speleothems) using both 14C carbon dating method and the uranium-thorium dating to obtain radiocarbon calibration curves (Hoffman et al., 2010).
Ancient fossilized animal and human footprints in Acahualinka, Nicaragua has been first estimated as 5,000 years old and later determined as 2,100 years old.

The Chauvet-Pont-d’Arc Cave in the southern France, discovered in 1994, contains the rock art, a treasure trove of Paleolithic masterwork paintings, prints, charcoal drawings of different animal species such as horses, lions, rhinos and bears, etched into the cave’s walls, and also fossilized remains, and markings of animals, some of which are now extinct (Herzog, 2012). Findings based on an analysis called geomorphological and chlorine-36 dating (36Cl Cosmic Ray Exposure) show that most of the art works were created by people who lived 28,000 to 40,000 years ago, in the Aurignacian culture of the early stages of the Upper Paleolithic, Late Stone Age; later on, an overhanging cliff began collapsing 29,000 years ago and did so repeatedly over time, definitively sealing the entrance to humans around 21,000 years ago. “This study confirms that the Chauvet cave paintings are the oldest and the most elaborate ever discovered, challenging our current knowledge of human cognitive evolution” (Sadier et al., 2008; Agence France-Presse, 2012). Bon et al. (2008) wrote, “We collected bone samples from the Paleolithic painted cave of Chauvet-Pont d’Arc (France), which displays the earliest known human drawings, and contains thousands of bear remains. We selected a cave bear sternebra, radiocarbon dated to 32,000 years before present, from which we generated overlapping DNA fragments assembling into a 16,810-base pair mitochondrial genome. … our study establishes the Chauvet-Pont d’Arc Cave as a new reservoir for Paleogenetic studies.“

A German film director Werner Herzog created in 2010 a documentary film about Chauvet Cave, Cave of Forgotten Dreams (2012) and won Best Documentary Award by several film critics groups. He rendered in 3D the curvature of the rocks to enhance the texture and depth of the art works on the cave walls. As described on his webpage, Herzog had been mesmerized, as a boy in Germany, by a book about cave paintings that he saw in a store window. He wrote, “The deep amazement it inspired in me is with me to this day. I remember a shudder of awe possessing me as I opened its pages.” (Werner Herzog, 2012). Cave of Forgotten Dreams was triggered by a Judith Thurman’s article in The New Yorker based on photos and interviews. Herzog became the first filmmaker permitted by the French Ministry of Culture to enter the cave, however under heavy restrictions. All people had to wear special suits and shoes that have had no contact with the exterior, stay on a two-foot-wide walkway, using only a small 3D-camera rig and three battery-powered light sources. Because of near-toxic levels of CO2 and radon in the cave, the crew could enter the cave for only a few hours each day. The cave explorers found, among rock paintings on a cave wall, some hand imprints with one finger shorter than others. This could be considered the first signature in art. In his film “Roma (1972) awarded at Festival de Cannes, BAFTA (British Academy of Film and Television Arts), and other festivals, an Italian film director and scriptwriter Federico Fellini devoted one episode to a sudden discovery of ancient Roman frescoes and sculptures that would conceivably happen during digging a tunnel for an underground metro. When the workers stunned by the majesty of the portraits on the frescoes pointed their flashlights toward the paintings in the newly discovered chambers, the faces on the walls became slowly bleach, whiten by exposure to light, and finally they disappeared.

The radiocarbon dating provided a key marker for the disastrous volcanic eruption (Minoan eruption of Santorini) that devastated the island of Santorini (also called Thera) close to the coast of Crete, and implications for the chronology of the Eastern Mediterranean cultures from the Bronze Age in the second millennium BC. The radiocarbon dating analysis of an olive tree buried beneath a lava flow from the volcano indicate, that the eruption occurred between 1627 BC and 1600 BC with a 95% degree of probability (Friedrich et al., 2006; Manning et al, 2006).

Occurrence

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Carbon is the fourth most common chemical element by mass in the universe. Hydrogen, helium, and oxygen are the first three most common. Carbon can be found in the sun, the stars, comets, and also in atmospheres of most planets. Some meteorites also contain tiny diamonds that were formed when the solar system was still gas surrounding a new-formed star. These tiny diamonds might also be formed when the meteorite impacts and the immense pressure and temperature that creates.

 

Along with most other planets, carbon is found in Earth’s atmosphere along with carbon dioxide and oxygen. We can also find it on Earth in the water dissolved. It is estimated that 36,000 gigatonnes of carbon is in the bodies of water on earth. About 1900 gigatonnes of carbon are in the biosphere. Carbon in the form of hydrocarbons such as coal, petroleum, and natural gas has about 900 gigatonnes on Earth. Oil reserves amount to about 150 gigatonnes. Carbon is also in abundance in the form of “unconventional” gases. The individual allotropes of carbon make up another large amount of substance. Graphite is very commonly found in the U.S., Russia, Mexico, Greenland and India. Diamonds are found in volcanic pipes. Most of these deposits are in Africa, however there are some in Arkansas, Canada, Russia, Brazil and Australia. Though most diamonds are found naturally, about 30% of diamonds in the United States are being made synthetically.

 

http://en.wikipedia.org/wiki/Carbon,

October 30, 2012, 1:17 pm

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November 6, 2012 1:02 pm

Allotropes

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There are three different allotropes (forms) of carbon that are commonly known. There are amorphous carbon, graphite, and diamond. There are also several fullerenes (substances made completely of carbon), which include carbon nanotubes and carbon Nano buds and Nano fibers. These things were once considered rare, but now are made commonly for use in research. There are also less well know and hard to find types of allotropes such as carbon nanofoam and glassy carbon, among others.

 

Amorphous carbon is a set of carbon atoms in an irregular, “glassy” state which is the basics of graphite except for the fact that it is not in a crystal-like structure at the Nano level. Its main form is a powdery substance and is the main substance in things like charcoal, soot and activated carbon (a form of carbon that has small holes that increase the surface area and make it easier for it to absorb other substances or chemical reactions).

 

Graphite is formed when carbon is at normal pressures. When it takes the form of graphite, the atoms of the carbon are bonded triagonally to three others in a “plane composed of fused hexagonal rings”. This leaves a network of 2-dimentional atoms and these sheets of flat carbon atoms are stacked and bond together. This is what makes carbon so soft and malleable.

 

The diamond form of carbon is formed when carbon is put under high pressures. Diamond has almost twice the density of graphite because of its compacted form. In diamonds, the atoms are bonded tetrahedrally to four other atoms, which makes it a “3-dimenstional network of puckered six-membered rings of atoms”. Silicon and germanium both have the same cubic structure as diamond. Also, because of the strength of the carbon-to-carbon bonds, diamond is one of the hardest naturally occurring substances when it comes to resistance to scratching. Under normal conditions, diamonds are thermodynamically unstable and will transform to graphite. The transition to graphite from a diamond state at room temperature is so slow that it is unnoticeable.

 

Fullerenes have a structure very similar structure to graphite, but instead of hexagonal bonding, they also contain pentagons and sometimes heptagons. This will turn the sheet of atoms into spheres, ellipses or cylinders. The fullerenes haven’t been fully analyzed yet. There is a lot of research to go before we fully understand what they can do. Buckyballs, a type of fullerenes, are large molecules formed out of carbon-bonded triagonally, which forms the spheroids (such as the buckminsterfullerene which is soccer ball shaped). Carbon nanotubes are bonded in also triagonally but form a cylinder shape.

 

http://en.wikipedia.org/wiki/Carbon,

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