pes of cellular signals (1) Chemical signals Hormones, neurotransmitters, growth factors, cytokines odor molecules; ATP, active oxygen; drugs, toxins, etc 2)Physical signals Light, electronic, mechanic, UV, heat, volume, osmotic, etc2. Types of cellular signals (1) Chemical signals Hormones, neurotransmitters, growth factors, cytokines; odor molecules; ATP, active oxygen; drugs, toxins, etc (2) Physical signals Light, electronic, mechanic, UV, heat, volume, osmotic, etc