Question

which of the following acts as a barrier between the outside and inside of the cell and is made of phospholipids and proteins?
the plasma membrane
the nucleus
a microtubule
a ribosome
the golgi apparatus
question 4
0.5 pts
the nucleus and the ribosomes work together to perform important functions for the cell. which of the options below correctly describe how the nucleus and ribosomes work together?
rna is made by ribosomes in the cytoplasm and is then transported into the nucleus.
all of the proteins of the cell are synthesized on ribosomes bound on the nuclear envelope.
none of the other answers options are correct.
the nucleus contains the genetic instructions for protein synthesis by the ribosomes.
the components of the ribosomes are first assembled in the cytoplasm and then transported into the nucleus to perform protein synthesis.

Explanation:

First Question (Cell Barrier)

To determine the cell structure acting as a barrier, we analyze each option:

• The plasma membrane is a phospholipid bilayer with embedded proteins, forming the cell's outer barrier.
• The nucleus is the control center, not a barrier.
• A microtubule is part of the cytoskeleton (structural support).
• A ribosome synthesizes proteins.
• The Golgi apparatus modifies proteins.

Thus, the plasma membrane fits the description.

To find how the nucleus and ribosomes work together:

• RNA is made in the nucleus (not ribosomes in cytoplasm), so the first option is wrong.
• Not all proteins are synthesized on ribosomes bound to the nuclear envelope (ribosomes are also free in cytoplasm), so the second option is wrong.
• The nucleus contains DNA (genetic instructions) that is transcribed to RNA, which is used by ribosomes to synthesize proteins. So "The nucleus contains the genetic instructions for protein synthesis by the ribosomes" is correct.
• Ribosome components are assembled in the nucleus (not cytoplasm first), so the last option is wrong.

Answer:

the plasma membrane

Question 4 (Nucleus and Ribosomes)