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Chapter 5: Problem 56

Globular proteins are typically constructed from several layers of secondary structure, with a hydrophobic core and a hydrophilic surface. Is this true for a fibrous protein such as keratin?

Short Answer

Expert verified
No, keratin does not have a hydrophobic core and a hydrophilic surface.

Step by step solution

01

Understand Protein Structures

Proteins can be classified based on their overall shape and structure into globular and fibrous proteins. Globular proteins typically have complex tertiary structures with layers of secondary structures making up their architecture, and are soluble in water due to hydrophilic surfaces and hydrophobic cores.
02

Characteristics of Globular Proteins

Globular proteins are often spherical and compact, with multiple secondary structures such as alpha helices and beta sheets forming a specific 3D arrangement. They usually have a hydrophobic core to stabilize the structure, while the outer surface is hydrophilic to interact with the aqueous environment.
03

Basics of Fibrous Proteins

Fibrous proteins, in contrast, are elongated and thread-like. They are typically insoluble in water and play roles in structural support due to their physical properties. Examples include keratin, collagen, and elastin, which form structures like hair, nails, and connective tissues.
04

Structure of Keratin

Keratin is a fibrous protein primarily composed of alpha-helices, forming long strands crossed-linked by disulfide bonds. Its structure is distinctly different from globular proteins as it does not have a hydrophobic core or an outer hydrophilic surface. Keratin's structure contributes to its strength and durability.
05

Conclusion

Keratin, a fibrous protein, differs significantly from globular proteins. It does not have a layered secondary structure with a hydrophobic core and a hydrophilic surface. Its primary function is structural, forming fibers that contribute to the mechanical properties of hair, nails, and skin.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Globular Proteins
Globular proteins are fascinating molecules that are generally round and compact in nature. Unlike fibrous proteins, they have a complex tertiary structure, primarily built from layers of secondary structures such as alpha helices and beta sheets. These structures intertwine to form a stable three-dimensional shape.
One of the most significant features of globular proteins is their solubility in water. This is because they have a hydrophobic (water-repelling) core and a hydrophilic (water-attracting) surface.
  • The hydrophobic core helps to stabilize the protein's structure internally.
  • The hydrophilic surface enables these proteins to interact effectively with the aqueous environment outside.
Their shape allows them to perform a variety of functions in the body, like transporting molecules or catalyzing reactions, making them incredibly vital for various biological processes.
Fibrous Proteins
Fibrous proteins are distinctly different from their globular counterparts. These proteins are elongated, thread-like, and are usually insoluble in water. They excel in providing support and strength to cells and tissues due to their unique physical properties.
  • They consist mainly of one type of secondary structure, often organized into long chains aligned in parallel.
  • Fibrous proteins have roles in structural support, providing strength and elasticity to tissues.
Examples include collagen, which provides structural integrity to skin, and elastin, which offers elasticity. They function less in chemical processes and more in maintaining the form and functionality of biological structures.
Keratin
Keratin is a well-known example of a fibrous protein. It's a primary component of hair, nails, and the outer layer of skin. Keratin is largely composed of alpha-helices, a type of secondary structure that coils into sturdy strands, supported by strong disulfide bonds between sulfur atoms in the protein.
  • These disulfide bonds are crucial for the protein's stability and rigidity, providing durability to the structures keratin supports.
  • The structure of keratin is not designed to interact with water, hence its lack of a hydrophobic core and hydrophilic surface.
Unlike globular proteins, keratin's role is centered on forming tough, durable fibers that enhance the mechanical properties of nails, hair, and skin. Its structural attributes, therefore, make it indispensable for protection and mechanical support in the body.

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Most popular questions from this chapter

People who live at or near sea level undergo high altitude acclimatization when they go up to moderately high altitudes of about \(5000 \mathrm{~m}\). a. The low \(p \mathrm{O}_{2}\) at these altitudes initially induces hypoxia, which results in hyperventilation. Explain why this occurs. What happens to blood \(\mathrm{pH}\) during hyperventilation? b. After a period of weeks, the alveolar \(p \mathrm{CO}_{2}\) decreases and the 2,3- \(\mathrm{BPG}\) concentration increases. Explain these observations.

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