Question

Intermediate filaments have been identified in ___________________.

	a.	plant cells
	b.	animal cells
	c.	all of these are correct answers
	d.	bacterial cells

Answer 1

The answer will be animal cells (Option b).

Explanation: Intermediate filaments (IF) are cytoskeletal compounds which provide mechanical support to the cell. They formed a 'hair' like structure & have size (average diameter is 10 nm) between actin (about 7 nm in diameter) & microtubules (about 25 nm in diameter). As their size falls between actin & microtubules they are called intermediate. Intermediate filaments are clearly found in several eukaryotic organisms including humans. So, option b is correct. Though intermediate filament protein like structure is detected in some plant cells (Ex. suspension cells of Daucus carota) & bacterial cells (crescentin), it is not widely accepted. Moreover unlike animal cells they show structural diversity in bacterial cells & their function is not clearly understood in plant cells. So, we can ignore options a & d. Thus, we can also ignore option c. So, the correct answer is option b.