This paper presents one of the ways in which the ideas of active learning, problem solving, using history of science, probing students' ideas and other approaches can be implemented to bring about meaningful learning. The example is taken from the plant chemistry and is suitable for the lower secondary level. In this paper we wanted to show how, from a seemingly simple question "What's inside a sweet pepper fruit", one can develop a complex teaching situation that leads to the realisation of teaching goals in a unique way. It shows merely one approach as an example of how to connect content (i.e. declarative knowledge, practical skills) and understanding of scientific processes (i.e. process-based knowledge), as well as the understanding of their own thought processes (i.e. metacognitive knowledge). The chemical analysis of the gases in the sweet pepper fruit showed that there was an increased concentration of carbon dioxide which is around 200 times greater than in the air and this is perhaps a good starting point for new problem-based teaching. (Contains 8 figures.)