Question

Porin proteins—which form large, water-filled pores in mitochondrial and bacterial outer membranes—fold into β-barrel structures. The amino acids that face the outside of the barrel have what kind of side chains? Choose one:

A. charged
B. hydrophobic
C. hydrophilic
D. amphipathic
E. polar

Answer 1

Proteins that form pores in mitochondrial and bacterial outer membranes have amino acids with hydrophilic side chains facing the outside of the barrel. These hydrophilic side chains allow for the transport of polar molecules and ions through the pores.

Step-by-step explanation:

Proteins that span membranes multiple times may include amino acids with charged, polar side chains, provided that these side chains interact between helices so that they are shielded from the fatty acid environment in the membrane. Because of these hydrophilic interactions, such proteins can create pores for the transport of polar molecules and ions; we will see some of these proteins later. Integral membrane proteins that do not span the membrane also have a hydrophobic helical domain that anchors them in the membrane, while their hydrophilic domains typically interact with intracellular or extracellular molecules to e.g., hold cells in place give cells and tissues their structure, etc.