4.3.3.P1
A. A common small-molecular weight (and therefore fast diffusing -- for an organic molecule) ingredient in perfumes is Vanillin, the primary component of vanilla bean extract (molecular weight = 152). The D for vanillin in air is 0.114 cm2/s. If I open a bottle of vanilla on the other side of the room 3 meters away, and the air is still so there is no convection, about how long would I have to wait before I could expect to smell the vanilla?
B. The diffusion constant for glucose in water is 0.70 x 10-5 cm2/s. About how much time would it take to get significant diffusion across the following structures?
- Across a cell membrane 8 nm thick;
- From the membrane to the center of a eukaryotic cell 6μm in radius;
- Across the wall of the human heart 2.5 cm in thickness;
- From photosynthetic cells on the surface of a barrel cactus to the center of the cactus if the cactus has a radius of 12 cm.
| C. The small lancelet amphioxus, is about 5 cm in length when adult. It absorbs oxygen through its skin. It develops a circulatory system, but this system does not have hemoglobin or another oxygen-binding molecule so the oxygen cannot simply flow withe the circulation. Instead, it must diffuse to all parts of the organism.
What are the implications for this organism of only using diffusion to move oxygen from the skin through the body cavity? The diffusion coefficient of oxygen in water is about 1.6 x 10-5 cm2/s. |
Source: Wikipedia commons
|
Problem by Todd Cooke, adapted by Joe Redish
Comments (0)
You don't have permission to comment on this page.