Rahul has gained weight because his muscle shape has changed. Regular exercise increase the body muscle as there is an enlargement of muscles due to increase in the amount of sarcoplasm and mitochondria and the strength he to developed led him gain the mass and size of body muscle and reduction in fat content.

(a) Due, to continuous exercise her muscles got fatigues because of the accumulation of lactic acid within skeletal muscles. Pain is also oftenly experienced in the fatigued muscles.

(b) Her breathing rate changes from normal to high as during exercise, her body muscle require more oxygen for the ATP production, than the normal value, hence her breathing enhances, to lake most oxygen from the atmosphere.

Gout is a disease, caused due to defect in purine metabolism. It causes accumulation of excess of uric acid and its crystals in the joints. The level of uric acid and crystals of its salts get raised in blood causing their accumulation in the joints causes gouty arthritis. The excess of urates in blood can also lead to the formation stones in the kidneys.

ATP (Adenosin Triphosphate) is the source of energy for muscle contraction. The head of each myosin molecule contains an enzyme called myosin ATPase.

In the presence of this enzyme along with $\mathrm{Ca}^{2+}$ then, and $\mathrm{Mg}^{2+}$ ions the ATP molecule breaks down into ADP and inorganic phosphate, thus releasing energy in the head of myosin.

$$\text { ATP } \longrightarrow \text { ADP }+P_i+\text { Energy }$$

Energy from ATP causes energised myosin to cross bridges and to bind with actin and in this way initiates muscle contraction.

Pectoral girdle Each half of the pectoral girdle consist of a clavicle and a scapula. The dorsal flat, triangular body of scapula has a slightly elevated ridge called the spine that, projects a flat expanded process called the acromion and the clavicle articulating with it.

Below the acromion their is a depression called the glenoid cavity which articulates with the head of the humerous to form the shoulder joint. Pelvic girdle consist of two coxal bones. each formed by the fusion of three bones, ilium, ischium and pubis. It articulates with femur through a cavity called acetabulum forming thigh joint.