Cellular and Molecular Biology
Question 1.
i. How have Eukaryotic cells solved the problem of moving proteins and organelles from one part of the cell to another, faster than would occur by diffusion? And give a specific example to illustrate how a protein may be moved from part of the cell to another.

The huge volume inside a eukaryotic cell is compartmentalized into a large number of bacterium-sized parts. Because eukaryotic cells are subdivided, the molecules required for specific chemical reactions are often located within a given compartment and do not need to diffuse long distances to be useful. Additionally, compartmentalization increases the efficiency of chemical reactions. First, the substrates required for particular reactions can be localized and maintained at high concentration within organelles. Second, groups of enzymes that work together can be clustered on internal membranes instead of floating free in the cytoplasm. Clustering these molecules increases the speed and efficiency of the reactions, because reactants have shorter distances over which to diffuse or be transported.

ii. An example to illustrate how a protein may be moved from part of the cell to another. For example, in localization sequencing a protein might be sent to the nucleus or marked for secretion outside of the cell. Additionally, in the SH2 domain , a protein domain is present in many signaling proteins. For example, the SH2 binds a short amino acid sequence containing a phosphotyrosine, and moves a protein containing it to sites in the plasma membrane in response to certain specific signals.
Describe one mechanism that ensures that proteins are moved to the appropriate place within a cell.
Localization Signaling or Tagging: Which are characteristics of short protein sequences that "tell" a cell where to send a protein. The tags are useful for separating as well