A hydrogen ion, often represented as H⁺, is a positively charged particle that forms when a hydrogen atom loses its electron. This ion is crucial in various chemical reactions and plays a significant role in the acidity of solutions. The concentration of hydrogen ions in a solution determines its pH level, which indicates whether the solution is acidic, neutral, or basic. In biological systems, hydrogen ions are essential for processes like cellular respiration and photosynthesis. They help maintain the balance of acids and bases in the body, influencing functions such as enzyme activity and metabolic pathways. Understanding hydrogen ions is fundamental in chemistry and biology.