PROBLEM I . The Part Leaves Flay in Making Food 



141 



Honey 



Grape 



Double Sugars (C12 H22 On 



Pofafoes 



Single Sugars (C6 Hi 2 Od) Starches (C6 Hio O5) KZM' 



Fig. 167 Did you believe that sugars and starches were rnade in factories? They are 

 made in plants. All we do is take them out of the plant, and theti refi?ie and pack them 

 in the factory. Which plants supply starches? Which supply sugars.'' 



It is a compound consisting of the three 

 elements carbon, oxygen, and hydrogen. 

 It is a sweet compound known as grape 

 sugar (CgHioOe). In most plants this 

 grape sugar is quickly turned to starch 

 (CgHioOg)!!. Both sugar and starch be- 

 long to a class of compounds called car- 

 bohydrates as you may recall (see page 

 no). You can show that the plant needs 

 chloroplasts to make sugar by perform- 

 ing Exercise 4. 



The process of sugar synthesis in leaves 

 was studied for many years before it 

 was understood. The process is still not 

 clearly understood, and only very re- 

 cently have chemists learned to imitate 

 imperfectly in the laboratory what plants 

 have always done within their green 

 leaves. Even now chemists can produce 

 only tiny amounts of sugar and starch. 

 Study Figure 1 67 to see where we obtain 

 most of our carbohydrates. 



