1)Give an example and explain the dependent of proteins on other proteins or molecules for their function?

2)Explain why 3' to 5' strand growth during DNA replication does not enable proofreading by DNA polymerase? 

3)Explain the importance of restriction points within the cell cycle.

4)Explain the principle of hydrophobic force and its role in protein conformation?  

1. Describe the structure differences between Euchromatin and Heterochromatin. How does these structural differences impact cell function?

1. One classic example is how protein's overall function is dependent on the shape of it and the other proteins around it. For proteins, there are four structural levels and each level allows for a specific type of bonding between proteins. For example, the primary structure of a protein is multiple amino acids joined by peptide bonds, commonly known as a peptide bond. Without the ability to form these peptide bonds, the functional proteins in our body would not have a stable backbone and almost all biochemical processes in the body would come to a halt. The secondary, tertiary and quaternary structures can not form without a stable primary structure. 

2. DNA polymerase uses energy from the 5' end of the nucleotide in order to initiate synthesis  to the 3' end of the leading strand. As DNA Poly continue through replication, they are able to proofread their work and detect if there is an incorrectly paired nucleotide. This process can only occur in the proper 5' to 3' orientation otherwise the proper energy from hydrolysis that DNA polymerase needs to "correct" its work would not be present. 

3. The restriction point is known as the G1 checkpoint. Without the regulation of G1 a cell with damaged DNA, incorrect size or inadequate energy will continue into the synthesis phase without being fixed and end up getting replicated. For a cell, the G1 checkpoint is the "all or nothing" point as once they pass through it is irreversibly committed to dividing.  

4. Hydrophobic (water fearing) interactions are key for keeping the protein stable and active within the body. This is because the hydrophobic effect is the main force in protein folding as the side chains into the interior. This folding decreases surface area and reduces chance of interacting with water. 

5. Heterochromatin is a firmly packed, genetically inactive form of the chromosome while euchromatin is loosely packed form of chromatin and therefor is genetically active. Since they are genetically active, it is only the euchromatin that participates in transcription.