The answer is the first one (A): IFs are linear, not globular monomers.
Explanation for each option:
A. IFs are linear, not globular monomers - Correct. Intermediate filament monomers are elongated and fibrous, unlike actin and tubulin monomers, which are globular proteins.
B. IFs bind to each other covalently - Incorrect. Intermediate filament monomers do not bind to each other covalently; they interact through non-covalent interactions to form the filament structure.
C. IFs do not bind and hydrolyze nucleotides - Correct, but not the distinguishing feature asked in the question. While it is true that intermediate filaments do not bind and hydrolyze nucleotides (unlike actin and tubulin), the question specifically asks for a property that distinguishes the monomers' structure.
D. IFs are glycosylated - Incorrect. Intermediate filament proteins are not typically glycosylated.
E. There are different types of IF monomers in different cell types - Correct, but not the distinguishing feature asked in the question. While it is true that there are different types of intermediate filament proteins in different cell types, this does not specifically address the structural properties of the monomers.
Summary:
The primary distinguishing property of intermediate filament monomers compared to actin or tubulin monomers is that IFs are linear, not globular monomers.
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