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3.1.3 Exchange of Materials

Cells
This is the structure of the epithelial cell of the small intestine under a microscope.




The fuzzy layer at the top is actually the microvilli.
The nuclei are the ovular shapes two thirds of the way down the shape.
The villi contain epithelial cells which…

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Transmission
The wavelengths of electron beams are much shorter than that of optical beams and so the images are a lot
more resolved.
A beam of electrons is passes to produce an image of the sample.
There are limitations in that the sample must be dead and all water must…

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The emulsion test for lipids
The way we test for lipids is fairly simple.
We break up the sample and add it to a test tube.
We then add ethanol and shake the contents thoroughly.
We leave the test tube to sit for a few minutes so that any remaining…

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o Gated channels open and close as they have hormone receptors. They open when a specific hormone is
delivered and this enables them to allow certain substances through, into the cell.
Facilitated diffusion relies on the kinetic energy of the molecules but it still doesn't require ATP from respiration like…

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