Answer:
iron
Step-by-step explanation:
Iron is essential element for the blood production. It is present in the heme unit of the hemoglobin. It is the one which binds to the molecular oxygen and transports it in the body.
Iron results in the increased formation of NADH by citric acid cycle which results in the increased oxygen consumption and also increased ATP formation by the process of oxidative phosphorylation.
Deficiency of iron cause blood loss which can cause anemia and also decreased oxygen consumption and its transportation which results in energy loss.