Biological reactions are processes that occur within living organisms, enabling them to grow, reproduce, and respond to their environment. These reactions often involve the transformation of substances through chemical changes, facilitated by enzymes, which are proteins that speed up these processes. Examples include photosynthesis, where plants convert sunlight into energy, and cellular respiration, where cells break down glucose to produce energy. These reactions are essential for maintaining life and are part of larger systems, such as metabolism, which encompasses all chemical reactions in an organism. Understanding biological reactions helps scientists develop medicines, improve agricultural practices, and address environmental issues.