270 



X-ray Analyses of Proteins and Nucleic Acids /1 5 : I 



H,C— O— C 



HC— O— G 



O 



Ci5H 31 

 O 



C 17 H 3 3 



O 



/ 

 H 2 C— O— C 



\ 

 (a) C 17 H 35 



O 



CH 3 CH 3 



HC— C 3 H 6 — CH— CH 3 



(b) 



H 2 C— O— C 



/ 



HpC— O— C 



/ 



HC— O— C 



/ 



HoC— O— P 



\ 



o 

 V R 2 



OH 



t 



i 



o 



HC— O— C 



/ 



o 



'f 



o 



/ 



R 2 



OH 



HoC— O— P 



CH, 



O— CHo— CH 2 — N 



(c) 



CH. 



\ 



O H OH 



I / 

 O— CH 2 — C— C 



I \ 

 NH 2 O 



CH, 



OH 



(d) 



Figure 2. A few lipids. Lipids are one general class of molecules found in all 

 cells. The phospholipids are a part of many cell structures, (a) Typical fat molecule; 

 (b) cholesterol (a steroid) ; (c) a-lecithin (a phospholipid) ; and (d) phosphatidyl serine 

 (another phospholipid). Many steroids act as hormones. The fats serve as storage 

 depots for chemical energy which is not rapidly available to the cells. 



100 and 1,000, which is small compared to those of proteins and nucleic 

 acids. 



Other molecules, found in all living cells, are called carbohydrates. 

 These consist of carbon, hydrogen, and oxygen atoms, the latter two 

 always occurring in the same ratio as in water. The carbohydrates 



