(Bio) Why are carbohydrates almost never on the INSIDE of the cell membrane?

[markelmarcel]

Homework Statement

Explain why carohydrates are found attached to integral membrane proteins on the outside, but almost never on the inside (cytoplasmic face) of cell membranes.

Homework Equations

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The Attempt at a Solution

Carbohydrates bond with integral membrane proteins on the outside to facilitate cell-to-cell recognition. It helps cells realize if they are the same or if they are not the same, whether it is something the cell wants, or something that may be harmful to the cell, etc.

What I can not find anywhere is any reasoning on why these carbohydrates are not on the inside?

My assumption would be that if they were on the inside then anything could get into the cell and by the time the carbohydrate realized it wasn't supposed to be there it would be too late. Also, the extracellular matrix is hydrophilic and so are carbohydrates... whereas to get through the membrane to the the inside of the cell you would need to be nonpolar so you could get through the hydrophobic phosolipid bilayer.

 

[nate808]

Additionally, the cytoplasmic face of the cell membrane is already lined with various proteins and molecules that perform important functions for the cell, so there may not be enough space or need for carbohydrates to be attached on the inside.

Moreover, carbohydrates on the inside of the cell membrane could potentially interfere with the cell's internal processes and signaling mechanisms. The inside of the cell membrane is where important molecules such as enzymes, receptors, and transport proteins are located, and adding carbohydrates to this area may disrupt their functions.

In summary, carbohydrates are found attached to integral membrane proteins on the outside of cell membranes to facilitate cell-to-cell recognition and communication, and to protect the cell from potentially harmful substances. They are not found on the inside of the membrane due to the hydrophobic nature of the membrane, the presence of other important molecules and proteins, and the potential interference with internal processes.

 

[Blueshift5]

Additionally, the inside of the cell membrane is already filled with various proteins and other molecules that play important roles in cell function, and adding carbohydrates to the mix may disrupt these processes. Therefore, it is more efficient and effective for carbohydrates to be located on the outside of the cell membrane where they can interact with other cells and molecules without interfering with the internal functions of the cell.