Question

Proteins can be classified into two types on the basis of their molecular shape, i.e., fibrous proteins and globular proteins. Examples of globular proteins are (A) Insulin (B) Keratin (C) Albumin (D) Myosin

Short answer

The given examples of globular proteins are Insulin (A) and Albumin (C).

Step-by-step solution

Understand the difference between fibrous and globular proteins

Fibrous proteins have a structural role in the body and are typically long, insoluble, and have a repeating structure. Examples include collagen and keratin. Globular proteins, on the other hand, are more compact, water-soluble, and usually have a functional role such as enzymes, hormones, or transport proteins.

Identify the protein types of the given examples

We will now analyze the provided examples to determine their protein type: (A) Insulin is a hormone that helps to regulate blood glucose levels. It is water-soluble, which makes it a globular protein. (B) Keratin is a structural protein found in hair, nails, and the outer layer of skin. It is insoluble and long, making it a fibrous protein. (C) Albumin is a water-soluble protein that helps regulate osmotic pressure and transport various substances in the blood. These properties classify it as a globular protein. (D) Myosin is a motor protein involved in muscle contraction. It is a long, fibrous protein that forms filaments.

Select the globular proteins from the list

Based on the analysis in Step 2, we can conclude that Insulin (A) and Albumin (C) are globular proteins, while Keratin (B) and Myosin (D) are fibrous proteins.

Key concepts

Fibrous Proteins

Fibrous proteins, as the name suggests, are long, thread-like structures that often form fibers or sheets. They have a primary role in providing support and strength to various tissues within the body. An intrinsic characteristic of these proteins is their insolubility in water, which is due to their polypeptide chains running parallel to each other, forming a rod-like structure.

Take keratin, for example. It is found abundantly in hair, nails, and the skin. Because of its sturdy and unyielding nature, keratin helps in providing rigidity and protection. Another well-known fibrous protein is collagen, which is crucial for the structural integrity of our skin, tendons, bones, and connective tissues. Understanding these proteins is not only important for JEE Chemistry but also for biotechnology, medicine, and material sciences where their unique properties are exploited.

Protein Structure

Proteins exhibit a complex structure, which can be studied at four different levels - primary, secondary, tertiary, and quaternary structures. The primary structure pertains to the sequence of amino acids in the polypeptide chain. Secondary structure involves the local folding patterns within the polypeptide, such as \( \alpha \) helices and \( \beta \) sheets, typically stabilized by hydrogen bonds.

The tertiary structure refers to the three-dimensional conformation of the entire polypeptide, including the interactions like hydrophobic interactions, ionic bonds, and disulfide bridges. Finally, the quaternary structure applies to proteins with multiple polypeptide subunits, illustrating how these subunits fit together. Understanding these levels is crucial for grasping how proteins function and how alterations in structure can lead to diseases or changes in biological activity.

Biomolecules in JEE Chemistry

In JEE Chemistry, the study of biomolecules encompasses a broad spectrum of organic compounds that are vital for life. It is an interdisciplinary topic that combines aspects from organic, inorganic, and physical chemistry. Biomolecules include carbohydrates, lipids, nucleic acids, and proteins. Each has a unique role to play in biological systems.

For instance, carbohydrates provide energy, lipids serve as structural components and storage for energy, nucleic acids store and transmit genetic information, and proteins perform a multitude of functions such as catalysis, support, transport, and defense. A deep understanding of biomolecules and their interactions is essential for aspiring engineers and scientists, which is why it is an integral part of JEE Chemistry syllabus. Highlighting their relevance, students are not only expected to understand their structure and function but also the role they play in various metabolic processes.