Which one of the following statements is NOT correct ?

Which one of the following statements is NOT correct ?

All proteins are enzymes
Mostly enzymes are proteins
All fats are energy rich compounds
Glucose is a common carbohydrate
This question was previously asked in
UPSC NDA-1 – 2017
Statement A is incorrect.
Enzymes are biological catalysts, and the vast majority of enzymes are proteins. However, not all proteins function as enzymes. Proteins perform a wide variety of functions in living organisms, including structural support (e.g., collagen, keratin), transport (e.g., haemoglobin), defence (antibodies), movement (actin, myosin), and signaling (hormones like insulin). Only a subset of proteins possesses enzymatic activity. There are also some non-protein enzymes, such as ribozymes (RNA molecules).
Statement B is correct: Mostly enzymes are proteins. Statement C is correct: Fats are a major source of stored energy and are thus energy-rich compounds. Statement D is correct: Glucose is a simple sugar (monosaccharide) and is a very common and fundamental carbohydrate, serving as the primary energy source for many organisms.