Figure 3. De novo fatty acid synthesis, but not the incorporation of exogenous fatty acids, increases as the cells divide. HeLa cells were synchronized by 2TB and released with fresh media as described under “Materials and Methods”. The cells were pulsed with (A) [¹⁴C]acetate, (C) [¹⁴C]glutamine, or (D) [¹⁴C]palmitate for 2 h prior their harvesting. The radioactivity associated to the lipid fraction was determined by scintillation counting and normalized to total protein content. (B) The incorporation of [¹⁴C]acetate into different lipid species was estimated by thin layer chromatographic analysis of total lipids and scintillation counting. The values are plotted as mean ± SD of a representative experiment (except for [B], in which only one experiment was done). *P < 0.05 ANOVA and Tukey.