Final answer:
Carbon is called the building block of life because it forms stable bonds with many elements, creating a vast array of complex molecules crucial for life, such as proteins and carbohydrates. Carbon's four-covalent bonds enable the formation of large, complex molecules that are the foundation of organic compounds in living organisms.
Step-by-step explanation:
Carbon is often called the building block of life because of its unique ability to form stable, long chains of molecules critical for the structure and function of organic compounds. Carbon atoms can form up to four covalent bonds, allowing for great versatility in the creation and variety of organic molecules. These molecules include proteins, carbohydrates, lipids, and nucleic acids, all vital to the structure and function of living cells. Additionally, organic molecules not only construct cellular structures but also enable biochemical reactions essential for life.
Almost all biochemically significant molecules, like DNA, enzymes, and hormones, are constructed with carbon as their backbone. The versatile bonding of carbon atoms facilitates the complexity and diversity of these organic compounds, without which life as we know it would not be possible. Moreover, carbon's ability to form double bonds and rings allows for the creation of an immense variety of molecular structures, not limited to the straightforward chains of atoms.
Ultimately, the significance of carbon in living organisms is underscored by its role in organic compounds, which carry out life processes and make up cells and other structures. The ubiquity and diversity of carbon-based compounds in living organisms and their capability to store energy further underscore carbon's central role in sustaining life.