The basic Elements that make up Life

There are more than 20 essential elements in living organisms, and four elements, Carbon, hydrogen, oxygen and nitrogen (C, H, O and N） are the main elements that make up cells, accounting for about 96% of human total weight.

Common essential elements include Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, calcium, chlorine, magnesium, iron, manganese, zinc, copper, boron, molybdenum (C, H, O, N, P, S, K, Ca, Mg, Fe, Mn, Zn, Cu, B, Mo, Cl) etc. Elements with content greater than 0.01% are called major elements, such as C, H, O, N, P, S, K, Ca, Mg; elements with content less than 0.01% are called trace elements or minor elements, such as Fe, Mn, Zn, Cu, B, Mo, Cl, etc. Although trace elements are very small in living organisms, they are components of enzymes, hormones and proteins, which are necessary for the life activities of living organisms. Thyroid hormones contain iodine and if the body is lacking in iodine, goiter will occur. Chlorophyll contains magnesium and if a plant is deficient in magnesium, it will appear the yellow leaves or even wither.

The most abundant element in the human body is oxygen, because various organic compounds contain oxygen atoms and two-thirds of the body weight is water(H₂O). Carbon is the second most abundant element since organics are made up of carbon chains or rings. The types of elements are roughly the same in different organisms, but their content varies greatly.

Among these elements, carbon needs to gain four electrons to form a stable structure. Therefore, carbon atoms share electron pairs with other atoms, such as Hydrogen, oxygen, nitrogen, phosphorus, and sulfur (H, O, N, P, and S), to form covalent bonds, and they are also connected to each other to form a long chain or a ring that makes the backbone of organics , resulting in various types of organic compound. Carbon is the basis of life on the earth.

Frequently Asked Questions

Why is cyanide very toxic to almost all living things?

Cytochrome C transfers electrons in aerobic respiration. It is a conserved protein and all organisms capable of aerobic respiration contain cytochrome C. Cyanogen will bind tightly to iron to destroy cytochrome C structure(the lone pair electrons from cyanogen will occupy the empty orbitals of iron to create coordinate covalent bond.), so that electron transport chain is destroyed. Then the reaction that produces the most energy in aerobic respiration cannot proceed. Organisms cannot survive due to the lack of energy.

Why silicon-based life does not exist on the Earth?

Silicon has a similar outermost electron structure to carbon. It has four electrons and needs to absorb other four electrons to reach a stable state. Some scientists have imagined a life where the silicon is used as the molecule backbone instead of carbon. These molecules containing silicon constitute silicon-based life. But this is only a conjecture of scientists, and silicon-based life cannot exist on Earth.

1. Silane, a compound of silicon and hydrogen, is unstable and easily reacts with oxygen and water.

2. The radius of silicon atoms is larger than carbon atoms, and the chemical bonds between silicon atoms are easily broken and cannot form a stable long chain, which results in silicon compounds being far less abundant than carbon compounds.

3. The silicon can easily combine with oxygen in chemical reactions to form silicates or silica. These substances are the basic components of the rock. It is not easy to get these very stable material back into the biosphere cycle.

4. It is also difficult for silicon-based organisms to exist in the universe because there is also a lot of water and ice in the universe, which can destroy the structure of silicon-based life.

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