a biologist conducts an experiment designed to determine whether a particular ty
ID: 10164 • Letter: A
Question
a biologist conducts an experiment designed to determine whether a particular type of molecule is transported in a cell by simple diffusion or active transport. he collects the following data:1.the molecule is small
2.it is polar
3.acculmulates inside a cell even when its concentration inside is initally is higher then outside the cell
4.cells use up more energy when the molecule is present in the enviorment around the cells then when its not present
He then concluded that the molecule moves across the cell membrane by facilitated diffusion. Is this the right conclusion he is making and why???
Explanation / Answer
The conclusion seems wrong. Remember that facilitated transport involves a fairly small, polar molecule which diffuse across the membrane. The molecule moves down its gradient using a protein channel. The process is only regulated by the opening/closing of the channel, and always goes from high to low concentration. In contrast, active transport involves a small or large molecule which is pumped against its gradient using some form of energy (either ATP or the potential energy of another gradient). It always goes low to high and is regulated by several stimuli. So, examine these observations: 1.the molecule is small -- could be facilitated diffusion or active transport. 2.it is polar -- could be either 3.acculmulates inside a cell even when its concentration inside is initally is higher then outside the cell -- this is impossible to do if using facilitated diffusion; must be active transport 4.cells use up more energy when the molecule is present in the enviorment around the cells then when its not present -- this is a hallmark of active transport because the cell is responding to stimulus (more of it present) and not only activating the channel, but using energy. This means the channel being activated isn't just a simple protein pore being opened. It is an active transport channel which requires energy to run. Hope this is useful.
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