Hydrogen bonds are weaker intermolecular forces between partially charged atoms or molecules, while covalent bonds are stronger intramolecular bonds involving shared valence electrons between atoms. To count pi bonds in ring structures, consider single, double, and triple bonds according to valence bond theory. The order in which bonds break during enzyme denaturation is hydrophobic interactions, then hydrogen bonds, then ionic bonds, with disulfide bonds not breaking via heat denaturation. Hydrogen bonds between water molecules are weaker than the covalent bonds within molecules and can be broken by heating without breaking covalent bonds. Common biological bonds include covalent, hydrogen, and van der Waals bonds as well as peptide bonds.

1. Your Questions About Bonds
Steven asks…
How are hydrogen bonds different from covalent bonds?
Hydrogen bonds are weaker than covalent bonds and form between partially charged atoms or
molecules.
The atoms in hydrogen bonds have valence electrons; the atoms in covalent bonds have
valence spaces.
The compounds that result from hydrogen bonds contain carbon; those that result from
covalent bonds do not.
Covalent bonds are organic; hydrogen bonds are inorganic.
Steve Winston answers:
The answer to your question is "Hydrogen bonds are weaker than covalent bonds and form
between partially charged atoms or molecules" ...
Hope this helps!!!
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2. Carol asks…
How do you count pi bonds on ring structures?
My teacher has given us several ring compounds and we have to determine the number of pi
bonds. One ring has two double bonds and within the ring there are an oxygen with two lone
pairs and a nitrogen with one lone pair. Oxygen is attached by single bonds on the ring while
nitrogen is a attached by one single bond and one double bond. Does that make any sense? So
its a cyclopentene but two of the carbons have been switched out with an oxygen and a
nitrogen. Please HELP!
Steve Winston answers:
Using Valence Bond Theory:
-Single bond = 1 sigma bond
-Double bond = 1 sigma bond + 1 pi bond
-Triple bond = 1 sigma bond + 2 pi bonds
So the compound you are describing has 2 pi bond.
Hope this helps
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3. Maria asks…
What is the order in which bonds break during denaturation of
enzymes?
When enzymes are heated, their bonds break and their polypeptide chain unfolds.. The bonds
occuring in enzymes are: hydrogen bonds, ionic bonds, disulphide bonds and hydrophobic
interactions.
Can someone tell me the order in which these break?
Steve Winston answers:
Hydrophobic interactions 1st because they are weakest.
Hydrogens bonds next
ionic bonds 3rd
disulfide bonds are covalent & won't break during heat denaturation. They need a reducing
agent like beta-mercaptoethanol to break them.
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4. Laura asks…
How do the hydrogen bonds between water molecules compare to
the covalent bonds within water molecules?
How do the hydrogen bonds between water molecules compare to the covalent bonds within
water molecules?
Hydrogen bonds are between two hydrogen atoms. Covalent bonds are between a hydrogen
and an oxygen.
The hydrogen bonds are more easily broken than the covalent bonds.
The hydrogen and covalent bonds are both polar.
The hydrogen and covalent bonds both involve electron sharing.
Steve Winston answers:
Hydrogen bonds are between one hydrogen atom which is delta + with a oxygen's lone pair on
another water molecule which is delta - Don't get too confused here, I'm basically saying one is
more electronegative than the other. Covalent bonds share electrons between the H2 and O2
atoms thus are much stronger than hydrogen bonds, which are much weaker intermolecularar
forces.
When you heat water you are actually breaking the H-bonds BETWEEN the molcules, it is
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5. extremly difficult to break the stronger covalent bonds within the atoms however.
Susan asks…
What types of bonds a present between atoms in biological
systems?
I have to create a chart to summarize bonds between atoms in biological systems but the only
2 kinds I can think of are ionic and peptide bonds. What other kinds are there? and what are
the bonds in the body like?
Thanks.
Steve Winston answers:
Covalent bonds are pretty prevalent, as are hydrogen bonds and van Der Waal's interactions,
which are really important in determing protein conformation. Those last two aren't "true" bonds,
but they do hold stuff together.
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