Enzymes are biological catalysts. Catalysts lower the activation energy for reactions. The lower the activation energy for a reaction, the faster the rate. Thus enzymes speed up reactions by lowering activation energy.
        
             
        
        
        
The parasympathetic nervous system <span>conserves energy as it slows down heart rate, increases intestinal and glandular activity, and relaxes the sphincter muscles of the gastrointestinal tract. It gets the nickname "rest and digest" for doing exactly so. Typically most active when sleeping, however is also the explanation for post-prandial fatigue, or being tired after eating (especially a large meal).</span>
        
             
        
        
        
Ribosomes synthesize proteins
        
                    
             
        
        
        
The answer is, D. Organ system
        
                    
             
        
        
        
The answer is cor-rectally FOSSIL FUELS
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