Carbon-doped　MgB2　polycrystalline　bulk　samples　were　prepared　by　reacting　mixtures　of　Mg　and　B　powders,　with　and　without　0.5　wt.%　of　the　amino　acids　glycine,　alanine,　valine,　leucine　or　isoleucine.　The　amount　of　carbon　introduced　into　the　MgB2　structure　depends　on　the　amino　acid　and　is　surprisingly　higher　for　glycine,　which　has　the　lowest　carbon　content　among　the　aliphatic　amino　acids.　The　critical　temperatures　of　samples　doped　with　all　kinds　of　additives　were　lower　than　for　the　undoped　sample.　The　critical　current　density　was　influenced　by　the　additives　to　different　extents,　alanine,　valine　and　leucine　yielding　the　best　results.　The　pinning　force　is　also　larger　for　these　additives　at　T　＜　30　K.　An　analysis　of　the　normalized　flux　pinning　force　behavior　leads　to　the　conclusion　that　point　pinning　is　predominant　in　all　samples.