General ---------Biology ------------------Online------------------   ----wilcox@sunline.net Ch.  2 :  The Chemical Context of Life

Look at three molecules: a sugar, an amino acid and a fatty acid, by clicking on their names below, and rank the elements present in a hierarchy from the most to the least numerous.

Sugar:   _____, _____, _____.
Amino Acid _____, _____, _____.
Fatty Acid _____, _____, _____.

In addition to organic molecules, such as these, the chemistry of living cells requires water, and lots of it.  The majority of the weight of your body is water, H₂O.  As a result hydrogen and oxygen are the most numerous elements in a living cell.

To see all 25 of the chemical elements the chemistry of life requires, click Table 2.1.

Nitrogen is a critical element, especially for cells to make amino acids; hook amino acids together into long chains and its called a protein.  A bag of lawn fertilizer is often labeled 20:10:6.  These numbers refer to the amount of nitrogen, phosphorous and potassium in the formulation.  Look at the corn field; which side of the field is deficient in nitrogen?

Look at the ingredients on vitamin container, and see how many of the "trace elements" that were listed at the bottom of Table 2.1 you can find.  Without these trace elements, many of the chemical reactions required to run a cell will fail resulting in diseases known as vitamin deficiencies.  Iodine deficiency, for instance, causes enlarged thyroid, a condition known as goiter.

Summary: 

• hydrogen, carbon and oxygen are the most common atoms in living tissue
• nitrogen is present in amino acids/proteins
• H, C, O and N make up 96% of the weight of living tissue
• trace elements are needed by living cells in minute (trace) amounts
• vitamins contain these trace elements
• a "goiter" is due to a diet deficient in the element iodine (I)