The background of this paper is an internal research project at the German National Research Center for Information Technology, Integrated Publication and Information Systems Institute, (GMD-IPSI) dealing with software engineering, computer-supported cooperative learning (CSCL) and practical biotech knowledge. The project goal is to develop a software framework in order to simplify the implementation of such virtual laboratories. The framework is called CoopLab because an important aspect of the framework is to enable cooperative learning in the virtual laboratory environment. (However, this functionality is still under development in the current state of the project.) The paper describes a constructionist approach as an enhancement of "instructionism" in virtual laboratory environments. It discusses learning in virtual laboratories from an "instructionist" and a constructionist viewpoint and relates them to virtual biotech laboratories developed as an application of the CoopLab framework. Virtual labs based on the CoopLab framework have the capabilities to meet the requirements of constructionist learning environments. A comparison to related work unveiled the specific potential of CoopLab applications to support constructionist learning. (Contains 15 references.) (AEF)