Exam 3 Andreas prep

Question 1

Which cell-cell connectors use cadherins to connect between adjacent cells?

Answer 1

Desmosomes and Adherens junctions (intracellular)

Question 2

Key properties of MTs?

Answer 2

1. MTs are hollow tubes that provide tracks for molecular motors.
2. MTs are polar structures with a highly dynamic plus-end and less dynamic minus-end.

Question 3

What are MTs interacting with?

Answer 3

1. Taxol
2. Dyneins and kinesins
3. MAPs

Question 4

What makes MTs so important for a cell?

Answer 4

1. Key element of the spindle during mitosis
2. Provide tracks for directed transport with molecular motors
3. Provide tracks for transport between cell center (nucleus ) and periphery
4. Pulling chromosomes apart during anaphase.

Question 5

What are the structural features of MTOCs?

Answer 5

1. In a metazoan cell, they contain two centrioles surrounded by the pericntriolar material
2. In a metazoan cell they are called centrosomes
3. In a yeast cell they are called spindle pole bodies and are inserted into the nuclear envelope
4. They contain gamma-TURC and gamma-TUSC

Question 6

Why would you want a protein to remove the GTP cap of a MT?

Answer 6

1. MT turnover is enhanced which produces more dynamic MTs

2. MTs need to shrink

Question 7

Which cells have NO MTs?

Answer 7

1. Mature mammalian erythrocytes (red blood cells)

2. Bacteria

Question 8

What defines a molecular motor?

Answer 8

1. Interacts with molecular track such as MTs or actin
2. Tightly regulated by ATP hydrolysis
3. Connect between track and cargo for directed transport processes.
4. Highly conserved motor domains but very variable cargo binding sites.
5. All motors generate about the same force of ~ 1-5 pN
6. Activity is regulated first by cargo-binding and then by track-binding (to avoid unnecessary ATP usage)

Question 9

Which regions in a kinesin motor domain control MT-binding?

Answer 9

1. The ATP binding site (part of switch-1 region)
2. Region that constitutes MT binding site (switch-II region)
3. Neck-linker region

Question 10

What separates a “walking” dimeric kinesin from a human walking on two feet?

Answer 10

1. Kinesin walks faster
2. Kinesin heads are identical (human feet are mirrored structures)
3. Kinesin heads stick to the MT surface by electrostatic interactions
4. Relative to its size, kinesins move much larger cargoes