General ---------Biology ------------------Online --------------------------- Ch. 3 Water and the fitness of the environment

You spill some food on your blouse or shirt and it leaves a light stain.  You wet a towel, blot the stain out, and when it dries the stain is gone... because the chemicals you spilled were "soluble" in water, or water soluble.

Most of the chemicals inside cells are water soluble; thus, "water is the solvent of life." For a story about freeze dried sperm, click here.  Fats or lipids are generally insoluble in water unless combined with other water soluble molecules. 

Question:  The presence of what atom determines if a molecule is soluble?  See if you can answer this by observing two molecules: a sugar that is soluble and a fatty acid that is not.  To see the two molecules, click here, then formulate a possible answer.  (Hint: "polar covalent bonds." "hydrogen bonds.")

Answer: _______________________________________________________. 

Proteins are often soluble in water if they contain enough oxygen, i.e. enough polar covalent bonds.  To see such a protein with a "hydrogen bond" to one water molecule, click here.  To see this protein surrounded by water molecules and held "in solution," click here  ...the numerous hydrogen bonds are not shown.

Read the definitions of solvent, solute and solution, on page 41 of the text.

Summary:  Students should write summary statements below as bullet points.