?Cell membranes contain proteins. Some of these proteins, involved in the transp

Question

?Cell membranes contain proteins. Some of these proteins, involved in the transport of molecules across the membrane into the cell, span the entire membrane and are called trans-membrane proteins (or integral membrane proteins). The interior of the cell membrane is hydrophobic and nonpolar, whereas both the extracellular and intracellular fluids are water-based.

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a. List 3 amino acid you would expect to find at the surface of the trans-membrane protein in the part that lies within the cell membrane. Explain your choice with one sentence.

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b. List 3 amino acids you would expect to find at the surface of the trans-membrane protein in the part that lies outside the cell. Explain your choice with one sentence.

Explanation / Answer

Answer :

a) The inner part of the cell membrane is hydrophobic / nonpolar. Therefore we would expect to find nonpolar amino acids such as Ala, Val, Leu, Ile, Phe,Met, Pro, Trp at the surface of the protein in this region.

b) The extracellular fluid is water, i.e. hydrophilic / polar. Therefore we would expect to find polar amino acids such as Ser, Thr, Tyr, Cys, Asn, Gln, Asp, Glu, His, Lys, Arg at the surface of the protein in this region.

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