Question

how does the structure of the phospholipid bilayer contribute to its function?
a. the hydrophilic heads face inward, allowing easy passage of water - soluble substances.
b. the hydrophobic tails face inward, creating a barrier to most water - soluble substances.
c. the hydrophobic heads face outward, creating a barrier to all substances.
d. the hydrophobic tails face outward, repelling water.
what is the sodium - potassium pump an example of?
a primary active transport
b. facilitated diffusion
c. endocytosis
d secondary active transport

Explanation:

• For the first question: Phospholipid bilayer has hydrophilic heads (face outward, interact with water) and hydrophobic tails (face inward, form barrier to water - soluble substances).
• For the second question: Sodium - potassium pump uses ATP (energy from hydrolysis of ATP directly) to move sodium and potassium ions against their concentration gradients. Primary active transport directly uses a source of chemical energy (like ATP) to move molecules against their gradient.

Answer:

1. B. The hydrophobic tails face inward, creating a barrier to most water - soluble substances.
2. A. Primary active transport