The cell cycle is composed of S (synthetic) phase and M (Mitotic) phase. In between are G1
and G2 phases. cyclin-dependent kinases propel cell division. Their activation
results in the progression of a cell from one
phase to another while their inactivation
arrests a cell in a phase. In case of
damage to DNA during a cell cycle, transcription factors p53 (a renowned tumor suppressor) are recruited. P53 inhibits
cyclins-dependent kinases and also
induces cell apoptosis if DNA is not repaired.
Answer: prokaryotic cells have no nucleus, no organelles and a small amount of DNA. Eukaryotic cells do have a nucleus, along with many organelles, and more DNA.
Breathing or respiration involves the inhale of oxygen into the lungs and exhale of carbon dioxide into the atmosphere. Cellular respiration involves the breakdown of glucose into carbon dioxide and water in living cells which in turn releases energy.
The two differences you see when comparing the four chambers of the heart is that the arteries have a thicker wall and veins have thin walls and that the arteries carry oxygenated blood away from the heart which means they get more pressure than veins.
