Alkanes ( also known as paraffins or saturated hydrocarbons ) are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds ( i. e., they are saturated compounds ) without any cycles ( or loops ; i. e., cyclic structure ).

Each carbon atom has 4 bonds ( either C-H or C-C bonds ), and each hydrogen atom is joined to a carbon atom ( H-C bonds ).

An alkyl group, generally abbreviated with the symbol R, is a functional group or side-chain that, like an alkane, consists solely of single-bonded carbon and hydrogen atoms, for example a methyl or ethyl group.

The three " R's " stand for carbon substituents or hydrogen atoms.

The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen.

In organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene or similar rings of atoms, and aliphatic compounds (; G. aleiphar, fat, oil ), which do not contain those rings.

Besides hydrogen, other elements can be bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine.

In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and more rarely other elements such as chlorine, bromine, and phosphorus.

If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with fewer hydrogen substituents ( Markovnikov's rule ).

It has likely exhausted its hydrogen and has begun fusing helium into oxygen and carbon in its core.

The yellow sphere is the redox | redox-active sulfur atom that provides antioxidant activity, while the red, blue, white, and dark grey spheres represent oxygen, nitrogen, hydrogen, and carbon atoms, respectively.

In today's chemistry the carbon, hydrogen, oxygen and nitrogen in a chimpanzee are identical to the same elements in a man.

Reactions with other nonmetals, such as carbon, nitrogen, phosphorus, silicon, and hydrogen, are generally exothermic and proceed upon heating.

Just six elements — carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus — make up almost 99 % of the mass of a human body ( see composition of the human body for a complete list ).

The simplest type of carbohydrate is a monosaccharide, which among other properties contains carbon, hydrogen, and oxygen, mostly in a ratio of 1: 2: 1 ( generalized formula C < sub > n </ sub > H < sub > 2n </ sub > O < sub > n </ sub >, where n is at least 3 ).

Just six elements — carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus — make up almost 99 % of the mass of a human body ( see composition of the human body for a complete list ).

The abundance of elements in Earth's crust differs from those in the universe ( and also the Sun and heavy planets like Jupiter ) mainly in selective loss of the very lightest elements ( hydrogen and helium ) and also volatile neon, carbon, nitrogen and sulfur, as a result of solar heating in the early formation of the solar system.

A carbohydrate is an organic compound that consists only of carbon, hydrogen, and oxygen, usually with a hydrogen: oxygen atom ratio of 2: 1 ( as in water ); in other words, with the empirical formula.

Examples of Lewis dot-style chemical bonds between carbon C, hydrogen H, and oxygen O. Lewis dot depictures represent an early attempt to describe chemical bonding and are still widely used today.

The CNO cycle ( for carbon – nitrogen – oxygen ) is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton – proton chain.

Argon ( αργος, Greek meaning " inactive ", in reference to its chemical inactivity ) was suspected to be present in air by Henry Cavendish in 1785 but was not isolated until 1894 by Lord Rayleigh and Sir William Ramsay in Scotland in an experiment in which they removed all of the oxygen, carbon dioxide, water and nitrogen from a sample of clean air.

In these compounds, at least one carbon atom is replaced by one of the heteroatoms oxygen, nitrogen, or sulfur.

In the presence of oxygen, alkenes burn with a bright flame to produce carbon dioxide and water.

Arcturus is likely to be around a billion years old, and has likely begun fusing helium into oxygen and carbon in its core.

This does not require oxygen ; if no oxygen is available ( or the cell cannot use oxygen ), the NAD is restored by converting the pyruvate to lactate ( lactic acid ) ( e. g., in humans ) or to ethanol plus carbon dioxide ( e. g., in yeast ).

This is why humans breathe in oxygen and breathe out carbon dioxide.

In animals with lungs, arterial blood carries oxygen from inhaled air to the tissues of the body, and venous blood carries carbon dioxide, a waste product of metabolism produced by cells, from the tissues to the lungs to be exhaled.

Plastics are made from synthetic carbon polymers, often with oxygen and nitrogen atoms included at regular intervals in the main polymer chain.

The extensive burial of biologically-produced carbon led to a buildup of surplus oxygen in the atmosphere ; estimates place the peak oxygen content as high as 35 %, compared to 21 % today.

When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water.

Incomplete combustion will only occur when there is not enough oxygen to allow the fuel to react completely to produce carbon dioxide and water.

Familiar examples of elements include carbon, oxygen ( non-metals ), silicon, arsenic ( metalloids ), aluminium, iron, copper, gold, mercury, and lead ( metals ).

Cosmic ray spallation ( fragmentation ) of carbon, nitrogen, and oxygen is important to the production of lithium, beryllium and boron.

)</ ref >< ref name = Socolow2011 > To the extent that carbon neutral fuels displace fossil fuels, or if they are produced from waste carbon or seawater carbonic acid, and their combustion is subject to carbon capture at the flue or exhaust pipe, they result in negative carbon dioxide emission and net carbon dioxide removal from the atmosphere, and thus constitute a form of greenhouse gas remediation .< ref name = Goeppert2012 > ( Review.

)</ ref >< ref name = Socolow2011 > To the extent that carbon neutral fuels displace fossil fuels, or if they are produced from waste carbon or seawater carbonic acid, and their combustion is subject to carbon capture at the flue or exhaust pipe, they result in negative carbon dioxide emission and net carbon dioxide removal from the atmosphere, and thus constitute a form of greenhouse gas remediation .< ref name = Goeppert2012 > ( Review.

Carbohydrates ( literally hydrates of carbon ) are chemical compounds, which together with proteins, lipids ( fats ), and nucleic acids ( RNA / DNA ), constitute the 4 principal biological macromolecules of which all life on Earth is composed.

) microbes, by virtue of their biomass alone, constitute the single largest carbon sink.

These elements along with calcium, sodium, potassium, magnesium, and carbon constitute over 99 percent of the solid mass of soils.

The carbon electrode is then heated to incandescence by collisions by ions which constitute the electric current.

It appears possible to set a lower limit of about Af for the activation energy of the abstraction of a chlorine atom from a carbon tetrachloride molecule by a chlorine atom to form Af radical.

Liter quantities of Mallinckrodt, low sulfur, reagent grade carbon tetrachloride were saturated with Af and Af and illuminated for about 50 hours with a 1000 watt tungsten lamp at a distance of a few inches.

As predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120 °.

The Brazilian Amazon sustains about 40 % of the world's remaining tropical rainforests and plays vital roles in maintaining biodiversity, regional hydrology and climate, and terrestrial carbon storage.

The most efficient composting occurs with a carbon: nitrogen mix of about 30 to 1.

A 40-year study of African, Asian, and South American tropical forests by the University of Leeds, shows tropical forests absorb about 18 % of all carbon dioxide added by fossil fuels.

Below a depth of about 1000 m, carbon dioxide is injected as a supercritical fluid, a material with the density of a liquid, but the viscosity and diffusivity of a gas.

But recent calculations suggest that carbon dioxide emissions from deforestation and forest degradation ( excluding peatland emissions ) contribute about 12 % of total anthropogenic carbon dioxide emissions with a range from 6 to 17 %.< ref > Deforestation causes carbon dioxide to linger in the atmosphere.

The price on the European market for an offset tied to a one-ton reduction in carbon is 23 euro ( about US $ 35 ).

Hemoglobin is involved in the transport of other gases: it carries some of the body's respiratory carbon dioxide ( about 10 % of the total ) as carbaminohemoglobin, in which CO < sub > 2 </ sub > is bound to the globin protein.

The carbon dioxide is bound to amino groups of the globin proteins as carbaminohemoglobin, and is thought to account for about 10 % of carbon dioxide transport in mammals.

I find it sad, but all too human, that there are vast bureaucracies concerned about nuclear waste, huge organisations devoted to decommissioning power stations, but nothing comparable to deal with that truly malign waste, carbon dioxide.

Ketones are trigonal planar about the ketonic carbon, with C-C-O and C-C-C bond angles of approximately 120 °.

Higher levels of carbon dioxide in the atmosphere are thought to have caused the world temperature gradient from north to south to become almost flat: temperatures were about the same across the planet.

The human body contains about 3 % by weight of nitrogen, the fourth most abundant element after oxygen, carbon, and hydrogen.

Ordinary nails for wood are usually of a soft, low-carbon or " mild " steel ( about 0. 1 % carbon, the rest iron and perhaps a trace of silicon or manganese ).

Glycolysis produces only 2 ATP molecules, but somewhere between 30 and 36 ATPs are produced by the oxidative phosphorylation of the 10 NADH and 2 succinate molecules made by converting one molecule of glucose to carbon dioxide and water, while each cycle of beta oxidation of a fatty acid yields about 14 ATPs.

For example geochemical signatures from rocks may help to discover when life first arose on Earth, and analyses of carbon isotope ratios may help to identify climate changes and even to explain major transitions such as the Permian – Triassic extinction event .< ref name =" Twitchett "> A relatively recent discipline, molecular phylogenetics, often helps by using comparisons of different modern organisms ' DNA and RNA to re-construct evolutionary " family trees "; it has also been used to estimate the dates of important evolutionary developments, although this approach is controversial because of doubts about the reliability of the " molecular clock ".

A much discussed source of carbon for recycling into fuel is flue-gas emissions from fossil-fuel combustion where it is proposed be obtainable for about USD $ 7. 50 per ton.

Researchers have estimated that carbon extraction from seawater would cost about $ 50 per ton.

The first photosynthetic organisms probably evolved about, early in the evolutionary history of life, when all forms of life on Earth were microorganisms and the atmosphere had much more carbon dioxide.