Efficiency of growth and product formation Y ATP The Y arp in the equation can be determined from growth yields and known routes of max ATP synthesis. For growth of Escherichia coli on glucose and mineral salts the Y ATP value, estimated from known cell composition and known biosynthetic pathways, is 28.8 g dry weight" ATP. However, the YATP determined experimentally from yield measurements is often around 50% of the theoretical (12 to 14 g dry weight mol ATP Explain the discrepancy between theoretical and experimentally derived values for y The discrepancy arises because aTP is used to drive processes which are not direct related to growth, eg membrane transport processes, protein tumover. These are called the maintenance and dissipation demands for AtP. For maintenance and dissipation we can write, simply: c(ATP+HO)→c(ADP+P) E-3.5 balance for Now lets consider the balance for nadh, ie: NADH NADH formation (energy source dissimilation (biosynthesis) oxidative phosphoryiation) To represent the balance for NADH using quantitative relationships, we must consider e degrees of degree of The degree of reductance of material is the number of available electrons per atom of reductance carbon and is determined using C(+4),H(+1), 0(-2)and N(-3) So, for biomass with an empirical formula of CH1.666No2 Ooz, the degree of reductance()is: (4)+(1x1.666)-(3x02)-(2x027=4526 What are the degrees of reductance of (1)co, (2)NH, and (3) 2H862Oa5 1? The degrees of reductance are( 1)0,(2)0 and (3)3.93. The answer for(3)was determined 4+(86.2/552x1)-(45.1/552x2) reduction For energy source dissimilation we can then write: aCHO, +Ho+ aNAD*->aCO,+5 a(NADH+H) E-3.6 Where: s=the degree of reductance of carbon substrate.Efficiency of growth and product formation 41 The Y Fg in the equation can be determined from growth yields and known mutes of max ATP synthesis. For growth of Exherich coli on glucose and mineral salts the Y value, estimated from known cell composition and known biosynthetic pathways, is 28.8 g dry weight mol-’ ATP. However, the Y determined experimentally from yield measurements is often around 50% of the theoretical (12 to 14 g dry weight mol-’ ATP). UlaX II Explain the discrepancy between theoretical and experimentally derived values max for Y ATP’ The discrepancy arises because ATP is used to drive processes which are not directly related to growth, eg membrane transport processes, protein turnover- These are dd the ’maintenance and dissipation’ demands for ATP. For maintenance and dissipation we can write, simply: c(ATP+HQ) -+ dADP+Pi) bahnca for Now lets consider the balance for NADH, ie: NADH E - 3.5 NADH formation = NADH utilisation (energy source dissimilation) (biosynthesis) (oxidative phosphorylation) To represent the balance for NADH using quantitative relationships, we must consider the degrees of reductance of substrate and products. The degree of reductance of material is the number of available electrons per atom of carbon and is determined using C(+4), H(+1), O(-2) and N(-3). So, for biomass with an empirical formula of CH1d02000.27, the degree of reductance ( $ is: degree of redmce (4) + (1 x 1.666) - (3 x 0.2) - (2 x 027) = 4526 n What are the degrees of reductance of (1) CG, (2) NH3 and (3) csS~Hsazols.~? The degrees of reductance are (1) 0, (2) 0 and (3) 3.93. The answer for (3) was determined as follows: 4 + (86.2/552 x 1) - (45.1/55.2 x 2) redudon balance For energy source dissimilation we can then write: CH, 0, + HQ + f NAD+ --> CQ + (NADH + H+) E - 3.6 Where: = the degree of ductance of carbon substrate