A lion's body cells perform many tasks at once; for example, some cells are involved in growing new claws and some cells help the lion keep breathing. Which is the most important factor that allows cells to keep accomplishing their many tasks?
A. New cells are continuously being made from old ones in the process of meiosis.
B. Cells are constantly producing usable energy in the form of ATP.
C. Cells contain DNA from two individuals, and the combined DNA is constantly resulting in genetic variation.
D. DNA is transcribing into RNA, and RNA is translating into proteins.

All living organisms ranging from microbes to a lion or whale requires energy to perform their life processes. The cells of living organisms like lion obtain energy by breaking down organic molecules (glucose) using oxygen to release CO2, water and ATP (energy currency in cells).

Lions like other living organisms absorb food molecules (high energy storage) after digestion, take them in and break them down in the presence of oxygen (aerobic respiration). The freed energy (ATP) is used to power the organism's movements and physiological functioning. To achieve this many task (life processes including respiration, producing new claws etc), lion cells (mitochondria) need to undergo aerobic respiration which involves three steps; Glycolysis, Kreb's cycle and Oxidative phosphorylation to produce 36 molecules of ATP.