PART I 



BIOLOGICAL CHEMISTRY 

 Some characteristics of the substances which make up Organisms 



CARBOHYDRATES 



Chief of physiological importance are : polysaccharides 

 (C G H 10 O r ,) n , monosaccharides (C 6 H 12 O G ), and disaccharides 

 (C^H^On) . 



I. POLYSACCHARIDES. 

 A. STARCH. 



1. ' Native Starch. Mount a scraping from a slice of potato in 

 water and examine under the microscope. Study the structure 

 of the starch grains. Draw. Run a drop of dilute iodine solution 

 under the cover-glass. What is the reaction? Perform the same 

 experiment with corn-starch, and arrow-root or some other type of 

 starch, noting carefully any differences. 



2. Polarization phenomena. Demonstration Starch grains ex- 

 hibit characteristic light and dark bands when viewed by polarized 

 light. Examine the starch under the micropolariscope. Notice the 

 change in position of the bands as the analyzer is rotated. Draw 

 carefully, making the drawing large enough to show details clearly. 

 The principle and descriptions of a polariscope will be found in 

 Carhart's Physics ( pp. 323-4 ) . The Nicol prism in the stage 

 of the microscope is the polarizer; that on the tube is the analyser. 

 Inserting a starch grain between these two prisms is comparable to 

 inserting a selenite plate between two Nicol prisms, except that 

 the starch grain is doubly refractive in crossed bands. Read care- 

 fully the account given in the Physics. 



3. Solubility. Grind a little commercial starch in a mortar and 

 shake with cold water. Filter and test the filtrate with iodine. 

 Test solubility in boiling water. Note character of the resulting 

 solution. Cool a portion of a strong solution in a test-tube and 

 note result. Dilute and filter. To dilute starch paste add a drop 



