Inorganic Compounds:
* Water (H₂O): The most abundant molecule in living organisms, but not a protein.
* Salt (NaCl): An ionic compound crucial for many biological processes, but not a protein.
* Minerals (e.g., Calcium, Iron): Essential elements for various biological functions, but not proteins.
Organic Compounds that are NOT Proteins:
* Carbohydrates (e.g., sugars, starches): Provide energy and structural support.
* Lipids (e.g., fats, oils): Store energy, form cell membranes, and act as hormones.
* Nucleic Acids (e.g., DNA, RNA): Carry genetic information and play a role in protein synthesis.
* Vitamins (e.g., Vitamin C, Vitamin D): Organic compounds essential for various metabolic processes.
Other Non-Proteins:
* Cellulose: A structural polysaccharide found in plant cell walls.
* Chitin: A structural polysaccharide found in the exoskeletons of insects and fungi.
* Hormones: Chemical messengers, some are proteins, but many are not (e.g., steroid hormones).
* Enzymes: Biological catalysts, many are proteins, but some are RNA molecules called ribozymes.
Key Concept: Proteins are complex molecules made up of amino acids linked together in specific sequences. Any molecule that does not meet this definition is not a protein.
