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 The Chemistry of the Cell


The living cell is a symphony of thousands of chemical reactions all miraculously timed and coordinated to perform all the functions necessary for life. 

Amazingly, this symphony has only a few major players; only six elements carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (sometimes called CHNOPS;>) make up about 98% of the mass of all living organisms. 

 Carbon  is a unique element with the remarkable ability to form strong, stable chemical bonds with other atoms (keeps you from falling apart.) Each carbon atom can form four bonds with other atoms. (Sometimes, two atoms will form more than one bond between themselves making a double bond or even a triple bond.)
  
This bonding ability allows carbon atoms to form chains of almost unlimited length. These chains can be closed on themselves to form rings or may branch wildly. This gives great variety to the kinds of molecules that carbon can form. Below are just a few examples of the many ways carbon chains can be arranged to form the skeleton for different molecules.

A variety of compounds illustrating the plethora of ways carbon can chain together to form molecules

 Atoms of hydrogen and oxygen and less frequently nitrogen, sulfur, or phosphorous are bonded to the carbon skeleton to form giant molecules called macromolecules. A few other elements may occur in trace amounts.

The four major types of macromolecules found in living cells—carbohydrates, lipids, proteins, and nucleic acids--are made of smaller, repeating subunits called monomers. The monomers are not always identical but they always have similar chemical structures. They are joined together by a series of chemical reactions in a process called polymerization to form large, complex molecules called polymers.

 The Four Major Types of Macromolecules Found in Living Cells

Macromolecule

Elements

Monomer

Polymer

example

Carbohydrate

C, H, O

Simple sugars

Polysaccharide

Starch

Lipids

C, H, O

Fatty acids & glycerol

Lipid

Fats, oils, waxes

Proteins

C, H, O, N, S

Amino acids

Polypeptides

Insulin

Nucleic acids

C, H, O, P

Nucleotides

Nucleic acids

DNA

The chemical diversity that polymerization allows living things is similar to the diversity that our alphabet allows our language. Although there are only 26 letters in our English  alphabet, our ability to join them together to form words gives us an almost infinite variety of possible words. Similarly, the monomer units of macromolecules can be arranged with an almost endless potential for variety.

The functions of macromolecules are directly related to their shapes and to the chemical properties of their monomers. The way the monomers are arranged in the macromolecule determines its shape and its function in the same way that the arrangement of the letters in a word determine its sound and meaning.

Much of a cell's activities involve the arranging and rearranging and bonding of macromolecules.  It is the job of DNA both directly and indirectly to coordinate and direct these activities.

An understanding of the structure and functions of carbohydrates and lipids is not particularly key to the understanding of molecular genealogy. However, it may be helpful to take a quick look at the structure and function of proteins before moving on to the nitty gritty of the nucleic acids (of which DNA is one.)

 

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This web is lovingly dedicated to the memory of
Mr. James Dorsey
who so graciously and enthusiastically
donated his DNA to solve our family mystery. 


Jim Dorsey
2/12/1930 — 4-30-2002

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