Question

Match the columns: Column I (A) Inflammation of joints (B) Protein of thick filament (C) Protein of thin filament (D) The central part of thick filament is not overlapped by thin filament Column II (1) H-zone (2) Myosin (3) Actin (4) Arthritis (a) A-1, B-2, C-3, D - 4 (b) \(\mathrm{A}-1, \mathrm{~B}-3, \mathrm{C}-2, \mathrm{D}-4\) (c) A \(-4, \mathrm{~B}-1, \mathrm{C}-2, \mathrm{D}-3\) (d) \(\mathrm{A}-4, \mathrm{~B}-2, \mathrm{C}-3, \mathrm{D}-1\)

Short answer

The correct set of matches from column I to II are: A-4, B-2, C-3, D-1. The correct option from the given choices is (d).

Step-by-step solution

Match term (A)

In column I, (A) refers to the 'Inflammation of Joints'. This term refers to a symptom which is characteristic of the disease named 'Arthritis'. Looking into column II, it can be matched with (4), thus the match is A-4.

Match term (B)

In column I, (B) refers to the 'Protein of thick filament'. This is refereeing to the composition of thick filaments in muscles, which are primarily made up of the protein named 'Myosin'. Looking into column II, it can be matched with (2), thus the match is B-2.

Match term (C)

In column I, (C) refers to 'Protein of thin filament'. Thin filaments in muscles are primarily composed of the protein 'Actin'. Looking into column II, it can be matched with (3), thus the match is C-3.

Match term (D)

In column I, (D) refers to 'The central part of a thick filament is not overlapped by thin filament'. This non-overlapping area in the skeletal muscle fiber is referred to as the 'H-zone'. Looking into column II, it can be matched with (1), thus the match is D-1.

Key concepts

Thick Filament Protein

Thick filament proteins are fundamental components of the muscular system. They are predominantly made up of myosin, which is a motor protein with the ability to convert chemical energy in the form of ATP into mechanical energy, thereby generating force and motion. Myosin molecules aggregate to form the thick filament, which is arranged parallel to the length of a muscle fiber.

Each myosin molecule has a tail and two heads, which bind to specific sites on the thin filament proteins during muscle contraction. This interaction is critical for the mechanism known as the sliding filament theory, where muscle shortening occurs due to the sliding of thin filaments over the thick filaments, powered by the myosin heads.

Thin Filament Protein

Actin is the primary protein making up the thin filament in muscle fibers. These filaments play a crucial role in muscle contraction by interacting with myosin, the thick filament protein. Actin filaments are composed of two intertwined strands that form a helical shape and have binding sites for myosin.

The thin filaments are anchored to the Z-lines of a muscle sarcomere and extend toward the center of the sarcomere where they partly overlap with thick filaments. It's this arrangement of thick and thin filaments that produce the striations observed in skeletal muscle cells, and functionally, the precise interplay between actin and myosin creates the contraction of muscle fibers.

Muscular System

The muscular system is an extensive network of muscle tissue that is responsible for movement, stability, and force generation within the human body. It includes three types of muscle: skeletal, smooth, and cardiac muscles. Skeletal muscles are connected to bones and are under voluntary control, aiding in locomotion and posture. Smooth muscles line the walls of internal organs and are controlled involuntarily, regulating processes such as digestion and blood flow.

Cardiac muscle is found only in the heart and is also involuntary, continuously pumping blood throughout the body. Muscles contract and relax through the action of proteins within muscle fibers, primarily actin and myosin, as well as through complex signaling pathways involving nervous input and biochemical reactions.

Inflammation of Joints

Inflammation of the joints, a symptom often described by pain, swelling, warmth, and sometimes redness around the affected area, can be an indicator of arthritis. There are various types of arthritis, such as osteoarthritis and rheumatoid arthritis, each with its own cause and mechanism.

Osteoarthritis is characterized by the degradation of cartilage in joints, leading to pain and stiffness, whereas rheumatoid arthritis is an autoimmune condition where the body's immune system attacks the joint linings. Managing joint inflammation involves a combination of medication, physical therapy, and sometimes surgical intervention, all aimed at reducing pain and improving joint function.

H-zone

The H-zone is the region in the center of the sarcomere, which refers to the repeating unit of a myofibril in a skeletal muscle cell, where only thick filaments are present. During muscle contraction, the H-zone becomes narrower as the actin filaments slide closer together. The H-zone's width is an indicator of the degree of muscle contraction, with a disappearing H-zone signifying full contraction.

This sliding of filaments to produce contraction does not occur in isolation; it is regulated by calcium ions and assisted by other proteins like troponin and tropomyosin, which control myosin head binding to actin.

Myosin

As the prime mover in muscle contraction, myosin functions through its ATPase activity, which hydrolyzes ATP to provide the energy necessary for contraction. The myosin head has a binding site for ATP and an actin-binding site, and it operates by attaching to an actin filament, performing a power stroke that pulls the actin filament inward, and then detaching to repeat the cycle.

Understanding myosin's structure and function is crucial for comprehending how muscle contractions occur at a molecular level, and myosin abnormalities can be involved in various muscle disorders and diseases.

Actin

Actin filaments, along with myosin, are integral to the contractile units of muscle fibers, known as sarcomeres. The proteins function together in a process where the heads of the myosin molecules walk along the actin filaments, pulling them inwards and resulting in the contraction of muscle cells. Actin is also involved in other cellular processes, including maintaining the cell's shape and motility. Actin's dynamic nature allows it to form and break down quickly, which is essential for cellular functions like cell division and movement.

Arthritis

Arthritis encompasses a group of conditions characterized by joint pain and inflammation. There are several forms, including osteoarthritis, rheumatoid arthritis, and psoriatic arthritis among others. Common symptoms across different types of arthritis include joint stiffness, swelling, reduced range of motion, and pain, which can be debilitating.

The causes vary with the type of arthritis; for example, osteoarthritis is often associated with wear and tear of cartilage, whereas rheumatoid arthritis is an autoimmune disorder. Treatment strategies aim to manage pain and inflammation, maintain joint function, and slow disease progression. These may include the use of anti-inflammatory drugs, disease-modifying antirheumatic drugs (DMARDs), lifestyle modifications, and in some cases, surgery.