you have to look at the electronegativity of each atom in the molecule, electronegativity is the ability of an atom to attract electrons. the more the electrons are attracted, the nearer they'll be, and the more negative the atom, giving rise to a polarised molecule. the simplest example is that of a water molecule, H2O.
Oxygen is much more electronegative (pulls electrons) than Hydrogen, so the result is that the Oxygen becomes slightly negatively charged, and the hydrogens become slightly positively charged, as their electrons are pulled away.
Now to apply this to an amino acid is quite simple, just look at the bonds it contains. For example an N-H bond leaves a slight negative charge on the N. a C=O bond leaves a slight negative charge on the O.
There can be other polarities depending on the electronegativity of the atoms involved, generally the elements go from more electronegative towards the towards the top right of the periodic table and less electronegative towards the bottom left. it is mostly to do with how large (more protons = more positive) the nucleus is and how much sheilding (more electrons = more same charge repulsion) the atom has.
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you have to look at the electronegativity of each atom in the molecule, electronegativity is the ability of an atom to attract electrons. the more the electrons are attracted, the nearer they'll be, and the more negative the atom, giving rise to a polarised molecule. the simplest example is that of a water molecule, H2O.
Oxygen is much more electronegative (pulls electrons) than Hydrogen, so the result is that the Oxygen becomes slightly negatively charged, and the hydrogens become slightly positively charged, as their electrons are pulled away.
Now to apply this to an amino acid is quite simple, just look at the bonds it contains. For example an N-H bond leaves a slight negative charge on the N. a C=O bond leaves a slight negative charge on the O.
There can be other polarities depending on the electronegativity of the atoms involved, generally the elements go from more electronegative towards the towards the top right of the periodic table and less electronegative towards the bottom left. it is mostly to do with how large (more protons = more positive) the nucleus is and how much sheilding (more electrons = more same charge repulsion) the atom has.
hope this helps