Living things are made of elements that form biologically important molecules
and compounds. Biochemical reactions involving these molecules and
compounds form the basis of life processes within cells.

Supporting Ideas:
9. Through experimentation scientists have discovered that atoms, which are
composed of protons, neutrons, and electrons, account for the different
properties of the elements.
10. Several elements, such as carbon, hydrogen, nitrogen, oxygen, phosphorus,
sodium, potassium, sulfur, calcium, and iron, form compounds that are necessary
for life.
11. Covalent, ionic, and hydrogen bonds result from the underlying structure of
elements. These bonds are formed or broken as molecules are assembled or
rearranged during metabolism.
12. Water is essential to biochemical reactions because of its physical and chemical
properties.
13. The chemical reactions of life require the maintenance of a narrow range of pH.
14. Experiments have shown that carbohydrates, proteins, lipids, and nucleic acids
provide the raw materials for the structure and functions of life. These biological
polymers are formed through dehydration synthesis.
15. Carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio,
which form monosaccharides, disaccharides, and polysaccharides. They are
used to store energy and provide support.
16. Proteins, formed of amino acids linked together, comprise a chief building
material of organisms and also act as biological catalysts called enzymes.
17. Lipids are macromolecules that are insoluble in water. They store energy and
are components of cell membranes.
18. Nucleic acids are long chains of nucleotides that contain the cell’s hereditary
information.
19. Metabolism includes all the chemical reactions involved in energy production,