Question

b. ______________ molecules can be either partially charged or fully charged.
c. since polar molecules like water, then ______________ molecules must not.

1. use the word hydrophobic or hydrophilic to complete the following:

a. ______________ molecules like to interact with water.
b. ______________ molecules do not like to interact with water.
c. ______________ molecules like to interact with hydrophobic molecules.

1. explain why water is called a polar molecule.
2. how does water dissolve sodium chloride (nacl) salt?
3. draw the phospholipid bilayer of the cell membrane (find a picture in the textbook or online). label the hydrophobic part and the hydrophilic parts. knowing that the cells cytoplasm (cytosol) is made up of a lot of water and that the environment outside the cell is very watery, explain why the phospholipid bilayer is oriented this way.

Explanation:

1.

• b. Polar molecules can have partial or full charges due to unequal electron - sharing.
• c. Non - polar molecules do not have partial or full charges like polar molecules.

2.

• a. Hydrophilic molecules are water - loving and interact with water.
• b. Hydrophobic molecules are water - fearing and do not interact with water.
• c. Hydrophobic molecules interact with other hydrophobic molecules.

1. Water is a polar molecule because the oxygen atom is more electronegative than hydrogen. This causes the oxygen to pull the shared electrons closer, creating a partial negative charge on the oxygen and partial positive charges on the hydrogens.
2. Water dissolves sodium chloride because the polar water molecules are attracted to the charged sodium (Na⁺) and chloride (Cl⁻) ions. The oxygen end of water is attracted to Na⁺ and the hydrogen end is attracted to Cl⁻, surrounding and separating the ions.
3. The phospholipid bilayer has a hydrophilic head (which contains a phosphate group) and hydrophobic tails (fatty acid chains). The hydrophilic heads face the watery cytoplasm and extracellular environment because they can interact with water. The hydrophobic tails face each other in the interior of the bilayer to avoid contact with water.

Answer:

1.

• b. Polar
• c. Non - polar

2.

• a. Hydrophilic
• b. Hydrophobic
• c. Hydrophobic

1. Oxygen is more electronegative than hydrogen, creating partial charges.
2. Polar water molecules attract and separate Na⁺ and Cl⁻ ions.
3. Hydrophilic heads face water; hydrophobic tails avoid water.