Which cytoskeletal element has a diameter of about 10 nanometres?

DSSSB 14 August 2024

Applied Anatomy

Easy

Appeared in: DSSSB 14 August 2024

Explanation

Intermediate filaments are one of the three primary components of the cell's cytoskeleton.
Their diameter is approximately 10 nanometers (ranging from 8-14 nm), which places them size-wise between the thinner microfilaments and the thicker microtubules.
Their main role is to provide mechanical strength and resistance to physical stress, acting like the 'ropes' of the cell.
Unlike microfilaments and microtubules, they are composed of a variety of different proteins, such as keratin in epithelial cells and vimentin in fibroblasts.

Option A: Centrioles are not filaments but complex organelles. They are cylindrical structures made of nine triplets of microtubules and have a much larger diameter, approximately 200-250 nanometers.
Option B: Microfilaments are the thinnest of the cytoskeletal elements, with a diameter of only about 7 nanometers. They are composed of the protein actin.
Option C: Microtubules are the thickest cytoskeletal elements, forming hollow tubes with an outer diameter of about 25 nanometers. They are made of the protein tubulin.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification and dimensions of cytoskeletal elements as background academic context rather than a clinical decision trigger.
Defects in intermediate filament proteins, such as keratin, can lead to genetic disorders like epidermolysis bullosa simplex, where the skin is fragile and blisters easily due to a lack of mechanical resilience.
The cytoskeleton is a target for some chemotherapy drugs. For instance, paclitaxel (Taxol) stabilizes microtubules, preventing them from disassembling, which halts cell division and is effective against certain cancers.
What if? If a question asked about the cytoskeletal element responsible for forming the core of microvilli, the correct answer would be microfilaments (actin filaments), which provide structural support to these cell surface projections.

How to Approach the Question

This is a factual recall question from cell biology/anatomy.
First, identify the key information required: the cytoskeletal element with a specific diameter of 'about 10 nanometres'.
Recall the three main types of cytoskeletal filaments and their relative sizes.
Mentally arrange them by size: Microfilaments (thinnest), Intermediate filaments (middle), and Microtubules (thickest).
Associate the approximate diameters with each type: Microfilaments (7 nm), Intermediate filaments (10 nm), and Microtubules (~25 nm).
Compare this knowledge with the options. 'Intermediate filaments' directly matches the 10 nm diameter specified in the question.

Concept Tested & Keywords

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E6 Physiology Ganong 27e Vol 1 Part 1 p. 49-51

E6 Anatomy Grays 43e Vol 1 Part 1 pp. 42-44, 39-41