The purpose of this study is to investigate the effects of the Engagement, Exploration, Explanation, Extension, and Evaluation (5E) learning cycle, conceptual change texts, and traditional instructions on 8th grade students' understanding of photosynthesis and respiration in plants. Students' understanding of photosynthesis and respiration in plants was measured using the test developed by Haslam and Treagust (F. Haslam, D. F. Treagust (1987) "Diagnosing secondary students' misconceptions of photosynthesis and respiration in plants using a two-tier multiple choice instrument," "J. Biol. Educ." 21, 203-211). The test was administered as pre-test and post-test to a total of 101 8th-grade students in three intact classes of the same school located in an urban area. The classes were randomly assigned as control and experimental groups. Students in the first experimental group (n = 33) received 5E learning cycle instruction, students in the second experimental group (n = 34) received conceptual change text instruction, and students in the control group (n = 34) received traditional instruction. Attitudes toward science and pre-test scores were used as covariates. A quasi-experimental design utilizing the analysis of covariance showed a statistically significant difference between the experimental and control groups in the favor of experimental groups after treatment. However, no statistically significant difference between two experimental groups (5E "versus" conceptual change text instruction) was found.