Proteins are the building blocks of life.

This is a standard, widely used description in science. True: standard biology references (textbooks, scientific encyclopedias) describe proteins as fundamental building blocks of living organisms. Mostly true: the references treat proteins as one of several essential building blocks (alongside nucleic acids, lipids and carbohydrates); this is the expected reading of the common phrase and is not a significant error. Mixed: authoritative sources broadly reject the description, while acknowledging that proteins have a central structural or functional role. Mostly false: proteins are described as minor or non-structural. False: the evidence shows proteins are not fundamental components of life.

Set before the research began.

1. E1 The Molecular Composition of Cells NCBI Bookshelf (NLM, NIH), citing Cooper GM, The Cell: A Molecular Approach, 2nd edition, Sinauer Associates · 1 January 2000

   “The most fundamental property of proteins, however, is their ability to act as enzymes, which, as discussed in the following section, catalyze nearly all the chemical reactions in biological systems.”

2. E2 Protein | Definition, Structure, & Classification Encyclopaedia Britannica · 30 October 2026

   “Protein, highly complex substance that is present in all living organisms.”

3. E3 2.3 Biological Molecules - Concepts of Biology | OpenStax OpenStax (Rice University) · 25 April 2013

   “There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and each is an important component of the cell and performs a wide array of functions.”

4. E4 Physiology, Proteins StatPearls via NCBI Bookshelf (NLM, NIH) · 14 November 2022

   “Proteins serve as structural support, biochemical catalysts, hormones, enzymes, building blocks, and initiators of cellular death.”

Independent references treat proteins as fundamental parts of living organisms. Britannica says they are present in all living organisms (E2), StatPearls lists 'building blocks' among their roles (E4), and Cooper's textbook calls their catalysis of nearly all biological reactions fundamental (E1). However, OpenStax names proteins as one of four major classes of biological macromolecules, along with carbohydrates, lipids and nucleic acids (E3). That matches the criteria's 'one of several essential building blocks' reading, which gives mostly true.