Tag: muscle tissue

Myoglobin is a protein found in the muscle cells of animals. It functions as an oxygen-storage unit, providing oxygen to the working muscles.
Thus, the correct answer is option (A), 'Muscles'.

Smooth muscles are the muscle tissues that contracts without conscious control (involuntary), having the form of thin layers or sheets. It is made up of spindle-shaped, unstriated cells with single nuclei and found in the walls of the internal organs such as stomach, uterus, bladder, intestine and blood vessels (veins, arteries) except for heart.
Thus, the correct answer is option D.

Structural proteins are fibrous proteins and form the largest class of proteins measured in terms of their total mass. Structural proteins include myosin, collagen, and keratin. 

The phosphagens are energy storage compounds, also known as high-energy phosphate compounds. They are chiefly found in muscular tissue in animals. ATP molecules can provide energy for only a few seconds of strenuous muscular activity. Thus muscle cells have backup energy storage compound, creatine phosphate, that can be stockpiled. The energy stored in creatine phosphate is transferred to ATP as needed. But during vigorous exercise, the supply of creatine phosphate is quickly depleted. Muscle cells must replenish their supplies of these energy-rich compounds. Chemical energy is stored in muscle fibers in glycogen, a large polysaccharide formed from hundreds of glucose molecules. Glycogen can be degraded, yielding glucose, which is then degraded in cellular respiration. When sufficient oxygen is available, enough energy is captured from glucose to produce needed quantities of ATP and creatine phosphate.

Three major types of skeletal muscle fibers have been identified in vertebrates: slow-oxidative, fast-oxidative, and fast-glycolytic. Slow-oxidative fibers are specialized for endurance activities such as swimming, running long distances like the marathon, or maintaining posture. They contract slowly and fatigue slowly. These fibers require a steady supply of oxygen. They derive most of their energy from aerobic respiration and are rich in mitochondria and capillaries. Slow-oxidative fibers are rich in myoglobin, a red pigment similar to hemoglobin in red blood cells, which stores oxygen. Myoglobin enhances rapid diffusion of oxygen from blood into muscles during strenuous muscle exertion. Because of the myoglobin, slow-oxidative fibers are red. Birds that fly have red breast muscles specialized to support sustained activity. In humans, the proportions of slow-oxidative and fast-oxidative fibers vary among individuals and from muscle to muscle in the same person.

Six actin filaments surround each myosin filament and the active sites of an actin filament are available to three different myosin filaments in the myofibril of skeletal muscle fibre.

Cardiac muscles are striated involuntary, Contract quickly and do not get fatigued.