Problem 22 - Objective Biology for NEET

Question

The hardest substance in vertebrate body is (a) Keratin (b) Dentine (c) Chondrin (d) Enamel

Step-by-Step Solution

Answer

The hardest substance in vertebrate body is Enamel.

Step 1: Understanding the substances

Keratin is a protein that makes up hair, nails, and the outer layer of skin. Dentine is a hard, bone-like substance that makes up most of a tooth. Chondrin is the firm, rubbery matrix found inside bones. Enamel, on the other hand, is the hard, outer surface of a tooth.

Step 2: Comparing the hardness

Upon comparing, it is found that Enamel is the hardest substance among the options provided.

Step 3: Select the answer

Therefore, the hardest substance in vertebrate body is Enamel.

Key Concepts

Enamel

Enamel is the outermost layer covering the crown of a tooth, making it one of the most fascinating substances in vertebrate biology. This translucent layer provides a protective barrier against mechanical damage and wear. Composed predominantly of hydroxyapatite, which is a crystalline calcium phosphate, enamel is acclaimed as the hardest substance in a vertebrate's body.
This incredible hardness has a functional role by allowing vertebrates to chew and break down a wide variety of foods. However, despite its strength, enamel is susceptible to acid erosion and cannot regenerate. Understanding the resilience and limitations of enamel is vital for dental health.

Dentine

Dentine is the significant bulk of a tooth structure, lying beneath the enamel. It is a dense, yellowish tissue that is harder than bone but softer than enamel. Formed by cells known as odontoblasts, dentine contains tiny tubules that communicate signals to the nerves in the pulp of the tooth.
Despite its strong nature, dentine is more porous than enamel and can be affected by tooth decay. Its role is crucial in providing support to enamel and flexibility to the tooth, preventing it from cracking under pressure. Careful maintenance of dentine integrity is essential for overall dental health.

Keratin

Keratin is a robust protein found in various parts of the vertebrate anatomy. It is the structural component for hair, nails, claws, and the outer layer of skin. Its fibrous and resilient nature helps protect the skin from damage and provides strength to hair and nails.

• Provides mechanical support
• Acts as a barrier against environmental stressors
• Essential for animals with claws or hooves for defense and mobility

Though not the hardest substance, keratin is critical for the protection and functionality of vertebrate bodies.

Hard Substances in Vertebrates

Vertebrates possess a variety of hard substances that perform protective and structural roles. These include enamel, dentine, and keratin. Each substance offers distinct advantages:

• Enamel: The hardest, protecting teeth during mastication.
• Dentine: Adds bulk and support to teeth, absorbing pressure.
• Keratin: Provides structural integrity to hair, skin, and nails.

Comparing these, enamel holds the title for hardness due to its unique chemical composition. Understanding these substances aids in appreciating how vertebrates have evolved resilience and versatility in their anatomy for survival.