Biology 121 - Cell Physiology

Thought Questions for Exam 1

Hao Nguyen


1.†† What is a GTPase?Name the different GTPases discussed in class?What might happen to cellular functions in their absence?Propose how a cell might be able to †† cope in their absence.


2.†† The vesicular transport of cargo molecules like proteins requires the function of three types of coat proteins:clathrin, COP I, and COP II.Why are all three required?††††††††††† Can one or two out of the three types be sufficient for this function?Why are there so many other types of proteins that are involved in regulating vesicular transport?†††† What happens to the pathway if one of these proteins is missing or present in a mutated, non-functional form?


3.†† Discuss the relationship among the following processes:flip-flop, membrane recycling via both vesicular transport and phospholipid exchange protein, and the function of flippase.(Does not apply to Fall 2009 lectures)


4.†† Describe the process of transmembrane transport into the endoplasmic reticulum.Why is this process necessary?Explain why this type of transmembrane transport can only move polypeptide across the membrane, but not folded proteins.


5.†† Also from lecture so far, we learned that many proteins and enzymes belong to specific families.Why should there be more than one protein for each cellular activity?Seems like a waste, donít you think?Isnít one protein/enzyme per activity enough?

6.†† Think about the importance of endosomes and vesicles, what is/are the function(s) of these transient organelles?What would happen to the endocytic and/or exocytic pathways if these organelles were absent?


7.†† Think about the types of molecules and/or atoms that are transported by diffusion versus passive transport (or facilitated diffusion) versus active transport.What are the differences and similarities between a carrier protein and a channel protein?


8.†† Can organelles still be transported from one area of the cell to another area in the absence of the cytoskeletons, especially if microtubules are missing?If so, how?If ††††††††††† not, why not?


9.†† What is the function of the polarity in microtubules (that is, why do they have a plus end and a minus end)?


10.How are microtubules involved in exocytosis and endocytosis?


11.Consider the different types of intracellular transport:gated-transport versus transmembrane transport versus vesicular transport.What are the differences and similarities among these types of transport?What is it necessary to have so many types?What might happen to the cell if one type of transport were absent?


12.What is/are the difference(s) between a Primary Cell Culture (Cell Strain) and Cell Line?What are the advantages and disadvantages of each type of cell culture?How might cell †††††††††† culture be used to help us understand processes that we've learned so far in class?


13.Why is Contrast important when viewing the image of an object under the microscope?What are the various methods to produce contrast?How does the production †††††† of contrast differ when working with live cells in culture from working with fixed tissues?