Question

Background: A team of biologists working with NASA finds a living, unicellular organism on Mars and brings it to their lab. The organism’s cell membrane structure is different than any found on Earth.

Reason for the investigation: The scientists want to determine whether the alien cell’s membrane allows diffusion to take place.

Question: How should they investigate what they want to know? Design an investigation that will allow the scientists to determine whether the alien cell’s membrane allows diffusion to take place. In your plan, be sure to take into account that scientists do not know whether the cell is photosynthetic.

Answer 1

To test for diffusion across the Martian organism's cell membrane, scientists can compare the transport of a known solute across that membrane with a control, in a controlled environment where solute concentration and temperature are well-regulated. Changes in solute concentration inside the cell and potential volume changes due to osmosis should be monitored, distinguishing between passive and facilitated diffusion.

Step-by-step explanation:

To determine if diffusion occurs across the membrane of the newly discovered Martian organism, scientists could conduct an experiment comparing the transport of a known solute or gas across a biological membrane, such as the Martian cell's membrane, with a control, such as an artificial membrane or one from a terrestrial organism. Considering that photosynthetic capabilities are unknown, a non-photosynthetic solute such as a salt or sugar could be used to avoid false positives from photosynthetic processes. The experiment should take place in a controlled environment where the solute concentration outside the cell can be precisely manipulated. This setup would create a concentration gradient, allowing the observation of diffusion if it occurs.

The change in concentration of the solute inside the Martian cell over time can be monitored using appropriate detection methods, such as spectrophotometry or labeled isotopes. Moreover, controlling the temperature during the experiment is critical, as it can affect membrane fluidity and permeability. If the Martian cell incorporates the solute from the environment, it suggests passage through the membrane by diffusion. However, further tests are necessary to distinguish between passive and facilitated diffusion.

Additionally, they must monitor the Martian cell's volume for changes, as water movement due to osmosis may accompany solute diffusion. A comparative study with known terrestrial organisms can add context to the membrane properties observed, like the adaptation of salmon to different water purity levels without causing cell damage. Overall, understanding the regulations of solute and water flow relative to the Martian cell's membrane integrity will be crucial for the experiment's success.