The carbon-nitrogen peptide bond is rigid, but rotation can take place about the N-Ca and the Ca-C bonds in a protein (Ca is the a carbon atom). These bond angles define the conformation of the peptide chain. Answer questions (a) and (b). A Ramachandran plot is given for reference. Which of the following most likely describes part of an observed alpha helix? phi = - 59 degree ;psi = +150 degree; many Ser residues phi = - 57 degree ;psi = -47 degree; many Pro residues phi = - 140 degree ;psi = +130 degree; many Val residues phi = +60 degree ;psi = +40 degree ; many Gly residues phi = - 60 degree ;psi = -47 degree; many Ala residues Which of the following would not likely occur in a beta sheet?phi = +60 degree ;psi = +60 degree; many Gly residues phi = - 51 degree ;psi = +153 degree; many Gly and Pro residues phi = - 120 degree ;psi = +120 degree; many Tyr residues phi = - 57degree ;psi = -49 degree; many Ala residues phi = - 139 degree ;phi = +135 degree; many Val residues