Cells that are metabolically active and use a lot of energy: include red blood cells. include white adipose (fat storage) cells. are found in the dermal layer, just under the skin. are densely packed with numerous mitochondria. generally are not found in the human body.

are densely packed with numerous mitochondria.

Explanation:

Mitochondria are considered as the energetic centers of the eukaryotic cells. These organelles (mitochondria) produce energy in the form of Adenosine Triphosphate (ATP) through the mechanism of cellular respiration, i.e., mitochondria are the organelles where aerobic phases of cellular respiration occur. In presence of oxygen, mitochondria convert chemical energy obtained from foods to ATP, which is the energy coin that cells use to carry out all their metabolic processes (e.g., reproduction, growth, development, etc). Thus, cells with high metabolic requirements need to have many mitochondria in order to produce more ATP.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.