The organelle that is the site of oxidative phosphorylation is: MCQ with Answer and Explanation

Explanation:
Archaeopteryx is a famous fossil that exhibits characteristics of both reptiles and birds, making it a classic connecting link. It had reptilian features like teeth, a long bony tail, and clawed fingers, but also avian features like feathers, wings, and a bird-like beak. It provides strong evidence for the evolutionary theory that birds evolved from theropod dinosaurs.

Explanation:
The sinoatrial (SA) node is a specialized cluster of cells in the right atrium near the opening of the superior vena cava. It generates electrical impulses spontaneously, setting the pace of the heartbeat, hence called the pacemaker. The impulse spreads to the atrioventricular (AV) node, then to bundle of His and Purkinje fibers. Normal SA node firing rate is 60-100/min.

Explanation:
The right atrium receives deoxygenated blood from the body via the superior and inferior vena cavae. It then passes to the right ventricle, which pumps it to the lungs for oxygenation. The left atrium receives oxygenated blood from the lungs via pulmonary veins, and the left ventricle pumps it to the body. Thus, the right atrium is the receiving chamber for systemic deoxygenated blood.