Figure 4.

Closed-system experiments at different yeast dry weights of 11 (a), 6 (b), and 4 mg/ml (c). In a, oscillations continue until the glucose is used up. (b and c) At lower weights oscillations are either marginally possible and die out before the glucose is used up (b) or die out quickly (c), but damped oscillations can be induced by perturbations with acetaldehyde at t = 1400 and t = 2100, as expected for a Hopf oscillator below the bifurcation point. In all three experiments, the initial glucose concentration was 25 mM.