CBSE Questions for Class 11 Medical Biology Locomotion And Movement Quiz 1 - MCQExams.com

• According to the structure, the joints can be classified into- fibrous, cartilaginous and synovial. 
• Fibrous connective tissue unites articulating bones without any joint cavity.
• Fibrous joints are mostly immovable, some slightly movable usually synarthrosis. 
• These joint can be found in human skull.

The shoulder joint also called the gleno-humeral joint is an example of ball and socket joint. It is formed between the scapula and the humerus bones. It is the major joint that connects the upper forelimb to the trunk. It is one of the most important mobile joints in the human body.

• An immovable joint has two bones joined together with little or no movement and where no joint cavity exists. 
• Another name for an immovable joint is synarthrosis, which means immovable. 

• The myofibril is composed of two types of filaments. They are thick filament(Myosin) and Thin filament(Actin).
  
• Increase in Ca++ level leads to the binding of calcium with a subunit of troponin i.e troponin-C on actin filaments and thereby remove the masking of active sites for myosin. Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
  
• Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament. Each meromyosin has the globular head which is an active ATPase enzyme and has binding sites for ATP and active sites for actin. Hence ATPase activity in muscle fibre lies with Head of heavy meromyosin.
• So, the correct answer is 'Head of heavy meromyosin'.

• Skeletal muscle fiber is made up of two types of filaments. They are thick filament (myosin) and thin filament (actin). Contraction of a muscle fiber takes place by the sliding of the thin filaments over the thick filaments.
  
• Myosin (thick) filament is also a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament. 
  
• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length
•  In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.
  
• So, the correct answer is 'Troponin'.

• The adult human skeletal system consists of 206 bones, as well as a network of tendons, ligaments and cartilage that connects them.
•  The skeleton serves six major functions: support, movement, protection, production of blood cells, storage of minerals and endocrine regulation. Hence, Production of body heat is not a function of the skeletal system.

• Myofibrils are composed of two types of filaments i.e thin filament (actin) and thick filament (myosin).
  
• Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively
  
• Each myosin (thick) filament is a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament (Myosin).
  
• Hence thick filaments in muscles are polymerized proteins of meromyosin.
• So, the correct answer is 'Meromyosin'.