Figure 4.

Nucleotide accumulation depending on catalysis of individual pathways. Changes in mean nucleotide concentration at equilibrium with increasing rates of nucleotide catalysis of specific pathways, using the same values as figure 3. (a) Slow ($K_C^N=\hspace{0.17em}{10}^{0.9}$) or (b) fast ($K_C^N=\hspace{0.17em}{10}^4)\hspace{0.17em}$rates of CO₂ fixation, assuming no cost to catalysis (α = 0). The red dotted line indicates the number of protocell divisions per day with nucleotide catalysis of CO₂ fixation alone (i.e. no catalysis of other synthesis pathways). Other parameter values are given in table 1.