1. Keystone Review – Cell Membrane 1.C – The polar water molecule is repelled by the nonpolar, hydrophobic, fatty acid tail. 2.D – Nucleic acids, such as DNA and RNA do not make up the plasma membrane 3.C – Protein channels provide a way for small molecules and ions to cross the plasma membrane.

2. Keystone Response – Cell Membrane Cl – O 2 Starch No. Chlorine is a polar molecule and charged molecules cannot pass through the cell membrane Yes. An oxygen molecule is small and nonpolar. Small, nonpolar, uncharged molecules can fit through the phospholipid membrane without assistance. No. Starch is a macromolecule. The size of this molecule prevents it from crossing the plasma membrane.

3. Keystone Response – Cell Membrane A.The cytoskeleton will be assembled in the loose ribosomes in the cytoplasm because it does not need to be exported out of the cytoplasm.

4. Keystone Response – Cell Membrane B. The hormone will be synthesized in the smooth ER, which synthesizes lipids and hormones. It will be sent to the golgi apparatus and packaged for export in vesicles.

5. Keystone Response – Cell Membrane C. The cell receptor will be assembled by ribosomes on the rough ER. It will be package into a vesicle that will be transported to the golgi apparatus, modified further, and packaged into a vesicle that will merge with the plasma membrane.