ABSTRACT
Tissues carr y ou t a n enormou s numbe r o f chemica l reactions. Collectivel y these
are referre d t o a s metabolism. Som e reaction s o r reactio n sequence s (ofte n re -
ferred t o a s metaboli c pathways ) creat e comple x molecule s fro m simple r mole -
cules, an d thes e processe s ar e the n calle d anabolism. M a n y reactions , however ,
serve t o brea k d o w n comple x molecule s int o simpl e molecules , an d thes e pro -
cesses ar e calle d catabolism. A m o n g th e latte r i s th e degradatio n o f foodstuffs ,
such a s proteins , carbohydrates , and fats . Ofte n thes e ar e degrade d t o C 0 2 a n d
H 2 0 , w h i c h are excreted by th e organism . The purpose o f doin g thi s is to acquire
useful energy , w h i c h is i n tur n require d for th e variou s life processes , includin g
muscle contraction , maintenanc e o f gradient s acros s membranes , cel l replica -
tion, an d intestina l motility .
