Question

for each statement below, write true or false.

1. the structure and properties of the cell wall allow it to be selective and maintain homeostasis.
2. the plasma membrane is a bilayer of lipid molecules with protein molecules embedded in it.
3. a phospholipid molecule has a nonpolar, water - insoluble head attached to a long polar, soluble tail.
4. the fluid mosaic model describes the plasma membrane as a structure that is liquid and very rigid.
5. eukaryotic plasma membranes can contain cholesterol, which tends to make the membrane more stable.
6. transport proteins span the cell membrane, allowing the selectively permeable membrane to regulate which molecules enter and leave a cell.
7. proteins at the inner surface of the plasma membrane attach the membrane to the cells support structure, making the cell rigid.

Explanation:

• Statement 7: The plasma membrane (not the cell wall) is selective and maintains homeostasis. The cell wall provides structural support.
• Statement 8: The plasma membrane is a phospholipid bilayer with proteins embedded (fluid - mosaic model).
• Statement 9: A phospholipid has a polar, water - soluble head and non - polar, water - insoluble tails.
• Statement 10: The fluid mosaic model describes the plasma membrane as fluid (not rigid). Molecules can move laterally.
• Statement 11: Cholesterol in eukaryotic plasma membranes helps in maintaining membrane stability.
• Statement 12: Transport proteins (channel and carrier proteins) span the membrane and regulate molecule passage.
• Statement 13: Proteins at the inner surface attach to the cytoskeleton (support structure) but do not make the cell rigid (cell wall does that in plant cells).

Answer:

1. False
2. True
3. False
4. False
5. True
6. True
7. False