Conformationally dependent ionization of the simplest amino acid, glycine, is studied by Penning ionization electron spectroscopy with velocity-resolved metastable He*(2(3)S) atoms. The observed He I ultraviolet photoelectron and Penning ionization electron spectra are reproduced by superimposed theoretical spectra, assuming thermal distributions of conformers, The conformations of amino acids are determined by analyzing the observed Penning ionization cross sections. peak shifts, and collision energy dependences of partial ionization cross sections (CEDPICS). The Penning ionization cross sections are governed by collisionally accessible exterior electron densities. When the amino and carbonyl groups are exposed to He* access, the nonbonding orbitals of N (n(N)) and O atoms (n(O)) give rise to strong hands. The observed negative peak shifts and negative CEDPICS for the nN and no orbitals suggest the presence of attractive interactions around their electron distributions. The most attractive wells are estimated to be similar to 400 meV in the direction of the nN orbitals by ab initio model calculations. A conformer possessing dual hydrogen bonds contributes predominantly to the spectra.