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4.2: Absorptive Lineup and Cell Membranes

  • Page ID
    1085
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    Having completed digestion in the small intestine, a number of compounds are ready for uptake into the enterocyte. The figure below shows the macronutrient uptake lineup, or what is ready to be taken up into the enterocyte.

    Figure 4.21.png

    Figure 4.21 The macronutrient uptake lineup

    From lipids, we have the lysolecithin (from phospholipid), 2-monoglyceride (from triglycerides), fatty acids, and cholesterol. From protein, there are small peptides (di- and tripeptides) and amino acids. From carbohydrates, only the monosaccharides glucose, galactose, and fructose will be taken up. The other macronutrient, water, has not been discussed so far because it does not undergo digestion.

    However, these compounds must now cross the plasma (cell) membrane, which is a phospholipid bilayer. In the cell membrane, the hydrophilic heads of the phospholipids point into the lumen as well as towards the interior of the cell, while the tails are on the interior of the plasma membrane as shown below.

    Figure 4.22 .png

    Figure 4.22 Plasma membrane of a cell

    The plasma membrane contains proteins, cholesterol, and carbohydrates in addition to the phospholipids. Membrane proteins, such as channels and pumps, are important for the transport of some compounds across the cell membrane. The figure and two videos below do a nice job of illustrating the components of the cell membrane.

    Figure 4.23.png

    Figure 4.23 Cell membrane1

    References & Links

    1. en.Wikipedia.org/wiki/File:Ce..._diagram_4.svg

    Videos

    Contributors and Attributions


    This page titled 4.2: Absorptive Lineup and Cell Membranes is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Brian Lindshield via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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