Skin cells are made of proteins, water, and fat. But brain cells are only made up of amino acids, which ca make protein.<span />
        
             
        
        
        
Using numerous tissue cultures will facilitate individuals perceive however cancer works, however it spreads, however it is attacked and eventually overwhelmed. Scientists will experiment with them while not being afraid that one thing can happen to the patient since they would not be victimization actual cancer patients, however rather a bit of tissue in a very research lab.
 
        
                    
             
        
        
        
Answer:
Scientist count the world humans population with an organization called The United Nations Population Division (UNPD), 
Explanation:
Which keeps track of the world population, projects that the world's human population will hit 7 billion on Halloween Day 2011. Admittedly, that is just an estimate: There's no way to know exactly how many people are alive at any given moment, and the true date that humanity's ranks will surpass 7 billion could come in the weeks or months before or after Oct. 31. Nonetheless, the UN's guess is the best there is.
 
        
             
        
        
        
thin walls.
a moist inner surface.
a huge combined surface area.