problem 1:

a) What role do microtubules play in intracellular transport?
b) Describe the structure of microfilaments and microfilament networks and describe how they are assembled and disassembled within a cell.
c) Outline two functions that microfilament networks play in cell motility.
d) What function of intermediate filaments have in eukaryotic cells?

problem 2:

a) What two key factors determine the specificity of Watson-Crick base pairing in B-DNA? For each of these factors, describe why this is the case.
b) What activity of E.coli DNA polymerase 1 is responsible for ensuring correct Watso-Crick pairing during DNAS synthesis?
c) Outline briefly how this activity (given in your answer to part (b)) is achieved by this enzyme.

problem 3:

a) What is a mitotic spindle?
b) Which to classes of motor proteins interact with spindle microtubules during mitosis?
c) What role do these motor proteins play in the process of mitosis?
d) A drug that prevents the assembly of microtubules is applied to a culture of dividing cells for four hours. How will the culture treated with the drug differ from an untreated culture of the same cells, in terms of the numbers of cells in different stages of the cell cycle? In your answer, you should describe how the difference in appearance arises.

problem 4:

a) Describe the cellular location and function of the following membrane-bound vesicles: (i) synaptic vesicle, (ii) phagosome.
b) Describe the roles of two of the following proteins associated with the formation of transport vesicles: Epsin, Dynamin, GGA-proteins, GTP-binding adapter proteins.
c) Give one ex of a transport vesicle that moves between the ER and the Golgi apparatus, indicating its coat protein and its direction of movement.