The analysis of similarities and differences in the understanding of the process of photosynthesis in students fifth graders and students first and third grade high school was determined realization of the concepts in elementary and high school education. Conceptual written test, and qualitative and quantitative analysis of the results was checked by the acquisition and conceptual understanding of concepts important for understanding the process of photosynthesis: relationship gases in the life processes of plants during the night, the importance of reactions to life on Earth, the impact of solar radiation on the process, the importance of water in the process and transfer of energy through the processes and food chains. The acquisition of content and linking these concepts in most students' predominant failure, while conceptual understanding achieved by only the most dedicated and successful students. Prescribed curricular content of nature and biology were followed presented content in the textbooks approved by the Ministry of Education for classes that participated in the conceptual testing, using for each class of two books by different authors. Their analysis is validated operationalization of textbooks in primary and secondary education and the existence of the conditions under which students can develop an understanding of the concepts of photosynthesis and related concept of breathing. Checked and misconceptions that occur among students and teachers in learning and teaching, and their retention throughout education, and some of the identified are: plant uses CO2 and converts it into O2 in photosynthesis, plants take oxygen at night, occurs because oxygen is required us to breathe, the sun gives plants sugar, light is needed for growth and development.