# Which atoms in a given amino acid are able to form hydrogen bonds with water?

Can anyone help me with this question I have tried everything. I know hydrogen bonding is with $\ce{F}$, $\ce{O}$, or $\ce{N}$, but every time I select those is says it's wrong.

• Which part of the question are you getting wrong? Top, bottom, or both? I'm guessing that if it's the bottom, then you need to include H in your list of H-bonding atoms to choose from. – jerepierre Sep 22 '14 at 23:06

The positive end of water can hydrogen bond with N, O, or F, as you said, but only if A) the geometry of the atom allows the water and N/O/F to get close to one another and B) the N/O/F has a lone pair of electrons. This happens at each of the green circled nitrogen and oxygen atoms. The red circled nitrogen is a decoy, as it is neither geometrically available nor does it have the appropriate configuration of electrons.

The negative end of water can hydrogen bond with hydrogen atoms that are attached to the N/O/F atoms, including the ones that are attached to the N atom that was not correct for the first part.