G1--- the cell is growing up feeding for 1
S-- the cell starts to repucate the chromosomes
G2--- the cell is growing for 2
<span>Centrosomes are made of from arrangement of two barrel-shaped clusters of microtubules, called “centrioles,” and a complex of proteins that help additional microtubules to form.</span>
In the human respiratory system, gas exchange occurs across the cells of the alveoli. Alveoli or an alveolus is the deepest part of the human respiratory system. This part of the respiratory system is a place where gas exchange between oxygen and carbon dioxide occurs from inhaled air to the blood cells<span>.</span>
