A protective protein which is the main structural component of hair, nail and epithelial cells is?

JSSH Staff Nurse - 2019

Applied Anatomy

Easy

Appeared in: JSSH Staff Nurse - 2019

Explanation

Keratin is a fibrous structural protein that is the key material making up the outer layer of the epidermis, hair, and nails.
It is classified into soft keratin (low sulfur content) found in the skin, and hard keratin (high sulfur content) found in hair and nails, which provides rigidity.
The primary function of keratin is to protect epithelial cells from mechanical stress and damage, and to form a protective barrier.
Its strength comes from extensive cross-linking between protein chains via disulfide bonds formed by cysteine residues.

Option B: Myosin is a motor protein, not a primary structural protein of epithelial tissues. Its function is to interact with actin to cause muscle contraction.
Option C: Collagen is the main structural protein of connective tissues like bone, tendons, and cartilage, providing tensile strength. While it is abundant in the dermis (the layer below the epidermis), it is not the main component of hair, nails, or the outermost epithelial layer.
Option D: Elastin's primary function is to provide elasticity, allowing tissues like the skin, lungs, and arteries to stretch and return to their original shape. It does not provide the rigid, protective structure characteristic of hair and nails.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Types and functions of structural proteins as background academic context rather than a clinical decision trigger.
The integrity of keratin is crucial for the skin's barrier function. Genetic mutations in keratin genes can lead to serious blistering skin disorders like Epidermolysis Bullosa Simplex, where the skin is extremely fragile.
In nursing, understanding the role of keratin is important for wound care and assessing skin integrity, as a compromised keratin layer can increase the risk of infection and fluid loss.
What if the question asked for the most abundant protein in the human body? The answer would change to Collagen, which is the main component of connective tissue throughout the body.

How to Approach the Question

First, identify the keywords in the question: 'protective protein', 'main structural component', 'hair', 'nail', and 'epithelial cells'.
Second, recall the major types of proteins and their primary functions in the body. The question is asking for a structural protein.
Third, evaluate each option based on the keywords. Think about where each protein is primarily found and what it does.
Keratin is specifically known for its role in forming hair and nails. Myosin is related to muscle. Collagen is the 'scaffolding' of connective tissue. Elastin provides stretch.
Eliminate the options that do not fit all parts of the description. Myosin, Collagen, and Elastin are not the main structural components of hair and nails.
Confirm that Keratin is the best fit for all the structures mentioned: hair, nails, and the outer epithelial cells of the skin.

Concept Tested & Keywords

Concept Tested: Types and functions of structural proteins
Stem keywords: protective protein, structural component, hair, nail, epithelial cells
Lead-in keywords: is

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