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EXCRETION OF GLYCOLIC ACID 231 



Tolbert: For Chlorella the C'^ labeled in the glycolate of the medium ap- 

 proaches a constant value after about 10 minutes. We are dealing with a dynamic 

 exchange of bicarbonate and glycolate across the cell wall and not an excretion 

 and continued accumulation in the medium of large amounts of glycolate. 



Amon : I don't know of any evidence for bicarbonate absorption by Chlorella. 

 But work has been done with roots, and roots absorb very little bicarbonate. 

 Is there any evidence that there is any bicarbonate absorption of the sort in algae? 



Tolbert : Not exactly. The evidence just presented was that glycolate excretion 

 occurred in medium at pH 5.5 or above and only in the presence of bicarbonate 

 ion. 



References 



1. Tolbert, N. E., and Cohan, M. S., "Products formed from glycoUc acid in 



plants," /. Biol. Chem., W4, 649-654 (1953). 



2. Zelitch, I., "The isolation and action of crystalline glyoxylic acid reductase 



from tobacco leaves," /. Biol. Chem., 216, 553-575 (1955). 



3. Smith, R. A., and Gunsalus, I. C, "Isocitritase: a new tricarboxylic acid cleav- 



age system," /. Am. Chem. Soc, 76, 5002-5003 (1954). 



4. Olson, J. A., "The d-isocitric lyase system: the formation of glyoxylic and 



succinic acids from d-isocitric acid," Nature, 174, 695-696 (1954). 



