The bile is produced by the liver and the gallblader only serves as storage between meals. The main stimulus for the release of bile from the gallblader comes from the nervous system,after food is put in the mouth.
        
             
        
        
        
Parenchyma
phloem
<span>xylem</span>
        
                    
             
        
        
        
DNA is composed of nucleotides, which are composed of three parts:
1. A five carbon carbohydrate (pentose)
Pentose is classified as a monosaccharide (simple carbohydrate), and its molecular formula is represented by  . They are water soluble molecules with sweet taste. Monosaccharides may have from three carbon atoms (trioses) to six (hexoses). In DNA is present pentose (5 carbon atoms)
. They are water soluble molecules with sweet taste. Monosaccharides may have from three carbon atoms (trioses) to six (hexoses). In DNA is present pentose (5 carbon atoms)
2. A nitrogenous base
Nitrogenous bases are ring-shaped compounds that contain nitrogen in their molecular structure. They are classified into two groups: purines and pyrimidines
The purine bases are adenine (A) and guanine (G). They are larger and contain more than one ring in their structure,.
The pyrimidines, cytosine (C), uracil (U) and thymine (T), are smaller and composed of a single ring.
3. One or more phosphate groups
A phosphate consists of a trivalent anion that contains one phosphorus atom and four oxygen atoms. Its molecular formula is expressed by  .
.
 
        
             
        
        
        
The best estimate for Earth's age is based on radiometric dating of fragments from the Canyon Diablo iron meteorite. From the fragments, scientist calculated the relative abundances of elements that formed as radioactive uranium decayed over billions of years.