Lecture 6 — 147 — Biochemical Problems 



siderable attention, however, has been devoted to the 

 absorption of sugar by animal tissues as governed by- 

 processes of phosphorylation. The view could be en- 

 tertained that phosphorylations and dephosphorylations 

 might create the necessary positive gradients, but it 

 has also been suggested that the energy of phosphate 

 bonds may be employed in accelerating the transport. 



No definite proposal has been made for an explana- 

 tion for the active transport of salt, such as occurs in 

 root cells, based on the phosphate-bond theory, but the 

 intimate relation between respiration and respiratory 

 inhibitors and the accumulation of salt stimulates 

 questions along this general line of hypothesis. It 

 may also be true that a connection exists between the 

 respiratory cycles, the building up and breaking down 

 of protein molecules, or protein complexes, and the 

 reactions of ions with basic or acidic groups of pro- 

 teins, in a dynamic sense. However speculative such 

 ideas may now be, it appears that progress in under- 

 standing the mechanism of salt accumulation will de- 

 pend largely on advancing knowledge of the bio- 

 chemistry of respiration, together with a correlation 

 of biochemical transformations with the maintenance 

 of organized structures in the protoplasm. 



REFERENCES :- 



Arnon, D. I. Ammonium and nitrate nitrogen nutrition of bar- 

 ley at different seasons in relation to hydrogen-ion concen- 

 tration, manganese, copper and oxygen supply. Soil Science 

 44: 91-121, 1937. 



, Effect of ammonium and nitrate nitrogen on the 



mineral composition and sap characters of barley. Soil 

 Science 48: 295-307, 1939. 



Brown, Allan H. and Goddard, David R. Cytochrome oxidase 

 in wheat embryos. American Journal of Botany 28: 319- 

 324, 1941. 



Chibnall, Albert Charles. Protein metabolism in the plant. 

 Yale University Press, New Haven, Conn., 1939. 



Clark, Harold E. Effect of ammonium and nitrate nitrogen 

 on the composition of the tomato plant. Plant Physiology 

 11: 5-24, 1936. 



