The Hydrogen Bond (or H-Bond), a partial intermolecular bonding, is considered to be of greatest importance in chemistry and biology. The H-Bond is responsible for keeping together water molecules, appears to be present in the protein α-helix secondary structure, and also has the crucial task of holding in place the two DNA strands.
In chemistry, water (H2O) has some peculiarities: in its solid state, ice, one water molecule is always surrounded by four other H2O molecules, but if brought back to its liquid state, thanks to higher temperature, it is forced to dismantle and loses its structured form (in nature, this fact can be observed as ice notoriously floats on water).
The H-Bond is also responsible for trees growing to their height; we are well aware that the atmospheric pressure can push a water column up to 10 meters high, and yet we all could see trees, like giant sequoias, that can easily grow to be 100 meters high.
How could water reach the top? The answer is the H-Bond.
In every vegetable organism exists a transport tissue called xylem that carries water from the plant roots to the other parts, like branches and leaves.
As explained before, in the liquid state water molecules are intertwined, like a link in a chain, thanks to the H-Bond.
When the phenomenon called evaporation (in other words, water loss) occurs, all water molecules in that chain act synchronically to replace the overflowing one and collect the new water absorbed by the roots on the ground.
ACTIVITY: In which topics of your biology course is hydrogen bond presented?