Answer:
Pepsinogen is produced by chief cells and is activated by hydrochloric acid secreted by parietal cells.
Explanation:
Pepsinogen is a proenzyme produced in the chief cells (that are located in the stomach lining) that, when gets activated, is transformed into pepsin - a peptidase with the function to degrade proteins into amino acids.
The reason why pepsinogen is released inactive is that it would break down all of the cell's proteins because of its proteolytic nature. For this reason, it is released as a proenzyme and gets activated when reaches the acidic environment provided by the hydrochloric acid secreted by the parietal cells, also in the stomach lining.
 
        
                    
             
        
        
        
This is possible because when a star dies, it basically expands to its maximum (explodes). Therefore, the materials of the exploded star mix with the primeval hydrogen of the Universe. Later, other stars are formed out of this mixture. Thats also how the sun was formed. :)
        
             
        
        
        
Answer:
A Elephant eats some grass
A lion rolls in the sand
Explanation:
Elephants and lions are biotic(living), and grass and sand are abiotic (nonliving) and those are two interactions 
 
        
             
        
        
        
Ocean plants absorb co2 just like trees do. Any co2 that’s not fixed will mess up the chemistry of the waters