Question

f. structures that convert nutrients to energy.
g. passageways where chemicals are made.
h. everything between the nuclear membrane and the cell membrane.
i. structure that manufactures ribosomes.
j. structure that contains dna and regulates genes.
(activity a continued on next page)
activity a (continued from previous page)

1. investigate: select the cell membrane. turn on show closeup. read the description, watch the animation, and answer the following questions below.

a. what kind of molecules can diffuse (go through) the cell membrane directly?

b. how can some large molecules and charged ions get through the cell membrane?

k. package created by the golgi apparatus.
l. small structure that synthesizes proteins.
m. sac that stores water, nutrients, or waste products.
n. tubules and filaments that give the cell its shape.

Explanation:

A. The cell membrane is a phospholipid bilayer; small, nonpolar molecules (like oxygen, carbon dioxide) can pass through its hydrophobic core directly via simple diffusion.
B. Large molecules (e.g., glucose) and charged ions (e.g., sodium, potassium) cannot cross the lipid bilayer directly. They require transport proteins—channel proteins for ions or carrier proteins for large molecules—to facilitate their movement across the membrane.

Answer:

A. Small, nonpolar molecules (e.g., O₂, CO₂)
B. Through transport proteins (channel or carrier proteins)