cytoskeleton II

Question 1

what forms microtubules? how is it done?

Answer 1

subunits of tubulin; Alpha and beta tubulin subunits bind GTP; alpha keeps it in structure, beta can use it

Question 2

how does growth occur in microtubule formation?

Answer 2

at beta end of tubule

Question 3

how do microtubules demonstrate dynamic instability? what does it mean?

Answer 3

= either catastrophe or rescue; sudden conversion from growth to shrinkage and vice versa

Question 4

what is catastrophe? rescue?

Answer 4

catastrophe = growth to shrinkage
rescue = shrinkage to growth

Question 5

where does nucleation occur in microtubule formation? what does this? is there a specific quantity that needs to be made?

Answer 5

Nucleation occurs in the MTOC (centrosome) using gamma tubulin and other proteins that serve as a “template” for the 13 protofilament structure

Question 6

what is the centrosome and what does it include? how does it relate to microtubule formation? when else is it important?

Answer 6

Centrosome is a microtubule organizing center (MTOC) with embedded centrioles and nucleation sites: important during mitosis; microtubules grow from here

Question 7

what is the function of kinetochore, non-kinetochore, and astral microtubules?

Answer 7

kinetochore = hold onto chromatin and centrosome
non-kinetochore = push/pull to separate cell
astral = anchor spindle poles to cell membrane

Question 8

what are cilia and flagella made of? what produces their movement?

Answer 8

Made from microtubules and motor proteins; axoneme

Question 9

what function does a flagella give a cell? what about cilia?

Answer 9

allows it to swim through liquid media (propels cell); beat rhythmically and move fluid over cell surfaces

Question 10

what is the difference bw cilia and flagella?

Answer 10

cilia are shorter, do not move cells

Question 11

what are 3 examples where cilia is found?

Answer 11

respiratory tract, gut epithelium, inner ear hair cells

Question 12

what is an axoneme? what is it made of?

Answer 12

core of cilium/flagellum; Made of microtubules and associated proteins in a special pattern

Question 13

Explain how bending works within microtubules.

Answer 13

Linker proteins stop microtubules from sliding, make them bend instead

Question 14

what is a disorder caused by hereditary dynein deficits? what does the disorder entail?

Answer 14

Kartagener syndrome; chronic lung disease due to insufficient movement of cilia; also embryonic development issues

Question 15

what causes Kartagener syndrome?

Answer 15

mutations on two genes on chromosome 9 cause defect in dynein arms; this leads to paralyzed cilia which causes syndrome

Question 16

what is primary cilia? what is its purpose? where can it be found?

Answer 16

nonmotile cilia that all cells have; Act as responder to external environment, serves as signaler or receptor (antennae); nasal epithelial cells

Question 17

where are intermediate filaments found? some examples of these filaments?

Answer 17

Found in vertebrate cells that are required to deal with mechanical stress (nuclear, epithelial, axonal)

Question 18

what characteristics about intermediate filaments makes it different from the other proteins?

Answer 18

do not contain a nucleotide binding site (not ATPases), not polar (both ends of the proteins are the same), not clear how they assemble

Question 19

what is the most diverse family of intermediate filaments? what do they do?

Answer 19

Keratins; These anchor to desmosomes or hemidesmosomes

Question 20

what happens to defective keratin?

Answer 20

Alterations in keratins lead to unusual “blistering” diseases, it no longer holds the cell in place

Question 21

what’s an example of a condition caused by keratin defects? what does it cause?

Answer 21

epidermolysis bullosa; skin ruptures or blisters with any mechanical stress

Question 22

where are neurofilaments important? where are they found and how do they contribute?

Answer 22

important in axons, esp. during development; these contribute to axonal diameter which is then important for speed of action potential

Question 23

what can alteration and accumulation of neurofilaments cause?

Answer 23

ALS- muscle atrophy and filament breakdown

Question 24

what is the function of growth cones? why do they do this?

Answer 24

find and form connections with other cells; grow or shrink based on environmental cues

Question 25

where are lamellipodia found? how do they function?

Answer 25

Tips of growth cones; filled with actin; myosin is required for contraction of cell

Question 26

what effect does a contact-mediated attraction/repulsion cue have on growth cones?

Answer 26

contact with an adhesion protein in the substrate (use adhesion protein as traction)

Question 27

what effect does a chemoattraction/chemorepulsion cue have on growth cones?

Answer 27

attraction to an emitted chemical cue

Question 28

what does embryonic development depend on and why?

Answer 28

Actin and tubulin are essential for embryonic development; bc it requires extensive cell movement

Question 29

what can a mutation on PIP5KI gene cause? what is it associated with? what can it lead to?

Answer 29

myocardial developmental defects; associated with impaired intracellular junctions; lead to heart failure and extensive prenatal lethality at embryonic day 11.5 of development

Question 30

why does the mutation in PIP5KI happen?

Answer 30

Actin disorganized and cadherin missing (calcium dependent adhesion protein)

Question 31

what other aspect depends on cell migration and adhesion? what condition can it cause if done incorrectly?

Answer 31

neural tube closure; spina bifida

Question 32

what are sertoli cells? what role do they play in kennedy disease? what are the symptoms of the disease?

Answer 32

respond to androgen and make sperm; alterations in the sertoli cell cytoskeleton during development produce infertility and facial/throat muscle weakness

Question 33

how are sertoli cells modified to cause the disease?

Answer 33

have altered cytoskeleton and lack androgen receptors on nucleus