Polarity

• Water is dipolar because it doesn't seem totally neutral to the "outside world." Since oxygen is electronegative, it tends to draw electrons away from its two hydrogens, adopting a net minus charge. Because of this, the hydrogens each carry a small positive charge.
  
  

Strength

• Although they are not full charges but merely partial ones, other atoms, also with small charges, are drawn to them. The resulting bonds are called hydrogen bonds. These bonds are not as strong as covalent or ionic bonds, yet they are immensely important.
  
  An excellent Shockwave animation by the Northland Community & Technical College (demonstrating the formation in water of hydrogen bonds) is cited below. It demonstrates how water molecules align themselves to form a network structure.
  
  The water molecules retain individual identity, even though they group together or "associate." Each molecule of water can form up to four hydrogen bonds.
  
  

Significance

• The first and most obvious significance is found in water, itself. Hydrogen bonding causes water to boil at a temperature significantly higher than it otherwise would. This prevents quick evaporation, a drying of the seas, and the loss of all life.
  
  Hydrogen bonding allows the formation of so-called "tertiary structure" (as an example, see Figure 1). Very large bio-molecules possess specific spatial orientations in large part because of hydrogen bonding.
  
  

Proteins

• Figure 2. Amide Cross-Linkage; Image by Author
  
  Proteins are an excellent example of why this is. The signature amide linkage of proteins can align two protein molecules (Figure 2). Such alignments don't always require different molecules. Much significant hydrogen bonding comes from within a single molecule.
  
  When multiplied a number of times in regular fashion in large molecules, these alignments produce helices and sheets essential to life. The "double helix" of DNA well illustrates the point.
  
  

Cosmetic

• Hydrogen bonding is significant to life, yes. It can also add beauty to life. The ability to curl hair exists, in part, because of hydrogen bonding. Bonds can be broken in straight hair, and reformed (along with sulfide linkages) to produce curled hair.