Which macromolecule is primarily responsible for chemical reactions in living organisms?

Proteins are primarily responsible for chemical reactions in living organisms due to their role as enzymes. Enzymes are specialized proteins that catalyze biochemical reactions, significantly increasing the rate at which these reactions occur. This catalytic ability is crucial for metabolic processes, allowing cells to carry out necessary reactions at the speeds required for life.

The structure of proteins, consisting of long chains of amino acids, allows them to fold into specific shapes that determine their activity. The unique three-dimensional structure of an enzyme's active site enables it to interact specifically with substrate molecules, facilitating the conversion of substrates into products. This specificity and efficiency make proteins essential for various functions, such as breaking down nutrients, synthesizing molecules, and regulating biochemical pathways.

Recognizing the foundational role of proteins in facilitating chemical reactions underscores their importance in the overall functioning of biological systems, making them essential to life.