Q. All enzymes are proteins. This statement is now modified because an apparent exception to this biological truth is

 2617  215 Delhi UMET/DPMTDelhi UMET/DPMT 2010Biomolecules Report Error

Solution:

All biological catalysts are not protein enzymes. RNA-based catalysts such as ribozymes and ribosomes are essential to many cellular functions, such as RNA splicing and translation. The main difference between ribozymes and enzymes is that RNA catalysts are composed of nucleotides, whereas enzymes are composed of amino acids.