CBSE Questions for Class 11 Medical Biology Locomotion And Movement Quiz 9 - MCQExams.com

A. Fibrous

Reason: A syndesmosis, a subcategory of fibrous joints. It is a slightly movable articulation where the contiguous bony surfaces are united by an interosseous ligament, such as the tibiofibular articulation.

• Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament.
• Each meromyosin has two important parts, a globular head with a short arm and a tail. The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.
• The globular head of a myosin molecule that projects from a myosin filament in muscle and is held to attach temporarily to an adjacent actin filament and draw it into the A band of a sarcomere between the myosin filaments to form a cross bridge.
  
• Cross bridges between actin and myosin are broken up by Binding of ATP to the myosin head and The myosin, releasing the ADP and P1 and muscle goes back to its relaxed state.
• So, the correct answer is 'Binding of ATP to the myosin head'.

• The Z discs come close together.
• The width of the I bands decreases.
• The width of the H zones decreases.
• There is, however, no change in the width of the A band.

$$\textbf{Correct Option B}$$

$$\textbf{Solution}$$

$$\bullet$$ $$\textbf{Option A}$$  Pepsin is a digestive enzyme which is found in the stomach that helps in the digestion of protein. Prolactin is a hormone which is produced in the pituitary gland and helps in lactation. This option is not correctly categorized.

$$\bullet$$ $$\textbf{Option B}$$ Troponin is a protein complex which is integrated in the muscle contraction in skeletal muscles and cardiac muscles. Myosin are motor proteins which are also involved in muscle contraction. This option is correctly matched.

$$\bullet$$ $$\textbf{Option C}$$ Secretin is a peptide hormone made up of 27 amino acids and it regulates the homeostasis throughout the body. Rhodopsin is not a polypeptide hormone rather it is a pigment which is present in the cells of the retina. This option is not correctly matched.

$$\bullet$$ $$\textbf{Option D}$$ Calcitonin is a peptide hormone secreted in the thyroid glands. Thymosin is also a hormone which is produced by the thymus and it helps in the development of T cells. This option is not correctly matched.

So, the correct option is B. 

• An immovable joint is an articulation between bones in which no movement occurs. It is also called a synarthrosis joint.
• It is of three types. They are sutures, syndesmosis, and gomphosis.
• Sutures are found between the bones of the skull, syndesmosis is the joint of the tibia and fibula in the ankle, and gomphosis between the root of a tooth and the sockets in the maxilla or mandible.
  
• Hence Synarthrosis is an immovable joint.
• So, the correct answer is 'Synarthros'.

• Sarcomeres are composed of thick filaments and thin filaments. The thick filaments lie at the center of the sarcomere and overlap the thin filaments. The thick filaments are comprised of an elongated protein, called myosin. 
• Each myosin molecule is shaped like a golf club, with the head of the golf club pointed out from the surface of the thick filament. 
• This structure forms the cross-bridge, that binds to the thin filament.