Question

a. label the hydrophilic and hydrophobic portions of the 3d integral protein.
b. what would happen to transport across the membrane if the protein did not fold correctly?

1. below is a simple illustration of a plasma membrane. for each type of molecule listed, perform the following tasks:
2. draw an arrow

• if the molecule can diffuse through the membrane, draw an arrow passing through the plasma membrane.
• if the molecule requires facilitated or active transport, draw an arrow bouncing off the plasma membrane.

1. justify your drawing for each type of molecule. one has been done for you.

• charged molecules (such as ions)
• gases (such as o₂, co₂, n₂)
• hydrophobic molecules

large polar molecules

large polar molecules: cannot diffuse across the plasma membrane because they cannot interact with the hydrophobic interior of the membrane. they require channel proteins or active transport.

Explanation:

a. The portions of the integral protein that interact with the aqueous environment (inside or outside the cell) are hydrophilic, while the portions that interact with the lipid - bilayer (hydrophobic core of the membrane) are hydrophobic.
b. If the protein did not fold correctly, its transport - related structures (such as channels or binding sites) may be misformed. This could lead to impaired or non - functional transport across the membrane as the protein may not be able to bind to or translocate the appropriate molecules.
For the plasma membrane transport tasks:

• Charged molecules (such as ions): Draw an arrow bouncing off the plasma membrane. Justification: The hydrophobic interior of the plasma membrane repels charged molecules, so they require facilitated or active transport.
• Gases (such as O₂, CO₂, N₂): Draw an arrow passing through the plasma membrane. Justification: Gases are small and non - polar, so they can diffuse through the lipid bilayer of the plasma membrane.
• Hydrophobic molecules: Draw an arrow passing through the plasma membrane. Justification: Hydrophobic molecules can interact with the hydrophobic interior of the lipid bilayer and diffuse through it.

Answer:

a. Hydrophilic portions interact with water; hydrophobic interact with lipid - bilayer.
b. Impaired or non - functional transport.
Charged molecules: Arrow bouncing off; repelled by hydrophobic interior.
Gases: Arrow passing through; small and non - polar.
Hydrophobic molecules: Arrow passing through; can interact with hydrophobic interior.