Question

1. a cell membrane is composed of a double layer of lipids in which many kinds of proteins are embedded. many of these proteins act like gates, allowing only certain particles to enter or leave the cell. when a particle has to go against its concentration gradient through one of these gates, energy is supplied by the cell to the correct protein to move the particle through the membrane. a sodium - potassium ion pump is an example of a type of carrier protein that uses a large portion of the cells energy to move sodium ions through the cell membrane.

what is a primary function of a cell membrane?
a. determining genetic traits
b. defending against foreign particles
c. breaking down proteins for energy
d. generating energy from mineral nutrients

Explanation:

The cell membrane is described as having proteins that act like gates, controlling particle entry/exit. Option a (genetic traits) is determined by DNA. Option c (breaking proteins) is a function of lysosomes. Option d (generating energy) is mitochondria's role. Option b (defending against foreign particles) aligns with the membrane's role of regulating what enters/leaves (can block foreign particles).

Answer:

b. Defending against foreign particles