Question

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?

1. investigate: select the nuclear membrane closeup. how is the nuclear membrane similar to the cell membrane?
2. investigate: select the mitochondrion closeup. what happens inside the mitochondrion?
3. investigate: select the ribosome closeup. how does the cell make proteins inside the ribosome?
4. investigate: select the vesicle closeup. how do vesicles move through the cell?

Explanation:

These answers are based on fundamental concepts in cell biology. The cell membrane's semi - permeability, the structure and function of organelles like mitochondria and ribosomes, and the movement mechanisms of vesicles are key topics in understanding cell function. The nuclear membrane shares structural and functional similarities with the cell membrane in terms of regulating substance movement.

Answer:

A. Small, non - polar molecules such as oxygen, carbon dioxide, and small lipids can diffuse directly through the cell membrane.
B. Large molecules and charged ions get through the cell membrane with the help of transport proteins. These can be channel proteins (for ions) or carrier proteins (for large molecules like glucose), and in some cases, through endocytosis and exocytosis for very large molecules.

1. Both the nuclear membrane and the cell membrane are composed of a phospholipid bilayer which acts as a semi - permeable barrier. They both regulate the movement of substances in and out of the enclosed space (the cell for the cell membrane and the nucleus for the nuclear membrane).
2. Inside the mitochondrion, cellular respiration occurs. This process includes the citric acid cycle and oxidative phosphorylation, which generate ATP (adenosine triphosphate), the energy currency of the cell.
3. The cell makes proteins inside the ribosome through a process called translation. Messenger RNA (mRNA) carries the genetic code from the DNA in the nucleus to the ribosome. Transfer RNA (tRNA) brings amino acids to the ribosome, and the ribosome links the amino acids together in the order specified by the mRNA to form a polypeptide chain, which will fold into a protein.
4. Vesicles move through the cell along the cytoskeleton (microtubules and microfilaments). Motor proteins such as kinesin and dynein "walk" along the microtubules, pulling the vesicles to their destination. Vesicles can also be moved by diffusion in some cases, especially over short distances.