Simple Model Cell Made from Scratch

A team of scientists at Penn State University is using a new approach to understand cells. They are starting from scratch. Many scientists start with something complex, such as an entire cell, and then delete genes one at a time to find what those genes do in the cell. Dr. Christine Keating, who led the research team, points out that her group is doing just the opposite. According to Keating, they are starting with a simple model cell to find out what is needed to simulate the most basic cell functions. Keating emphasizes that their goal is not to make a real cell. Rather, they want to understand the physical principles that govern biological systems.

The teams model cell is made up of cytoplasm surrounded by a cell membrane. The cytoplasm is a mixture of two somewhat gelatinous fluids. The two fluids do not mix, so one surrounds the other much as egg white surrounds an egg yolk. The cell membrane is made up of several types of lipids.

Researchers exposed the model cell to a concentrated sugar solution. Water diffused out of the cell and into the surrounding sugar solution. As a result, the volume of the cell decreased, leaving a membrane that was now too large for its contents. The cell changed to a budded form that looks like the two overlapping circles of a Venn diagram. The two fluids separated from each other based on their different interactions with the cell membrane. The cell exhibited a distinct polarity: one substance filled the main cell body, and the other substance filled the cell bud. “Polarity is critical to development,” stated Keating. “It is an important first step . . . in which different cells perform different functions.”

The next step for the research team involves making a cascade in polarity. “Now,” says Keating, “we want to find out what will happen if, for example, we add an enzyme whose activity depends on the compositions of the cytoplasm and cell membrane.”

More to Explore