Cytoskeletal

Front 1

What are the three basic classes of cytoskeletal elements?

Back 1

1. Microfilaments
2. Intermediate filaments
3. Microtubules

Front 2

What are microfilaments made of?

Back 2

Actin molecules

Front 3

What do actin molecules polymerize to form?

Back 3

Microfilaments

Front 4

What is the primary function of actin microfilaments in muscle cells?

Back 4

To generate contractile force. They are a part of the sarcomeres.

Front 5

List four functions of microfilaments in non-muscle cells.

Back 5

1. Motilitiy
2. Contraction
3. Membrane protrusion
4. Cytokinesis

Front 6

In what sort of a pattern do actin molecules assemble?

Back 6

Twisted double strand.

Front 7

Which cytoskeletal elements are polar?
What is the functional relevance of the polarity?

Back 7

Microfilaments and microtubules. This means that they assemble at one and end disassemble at the other end.

Front 8

Are microfilament assembly and disassembly ATP dependent?

Back 8

Assembly is NOT ATP dependent.

Disassemble is ATP dependent.

Front 9

What non-actin proteins control microfilament assembly?

Back 9

Actin-binding proteins

Front 10

Where in the cell are microfilaments found?

Back 10

They are found scattered throughout the cytoplasm without any centeral organizing structure, but they are also concentrated at the periphery of the cell. (Remember, they are key to some kinds of motility).

Front 11

Name four structures or processes that are dependent on actin.

Back 11

1. Microvilli
2. Stress fibers (they give a cell its shape)
3. Protrusive structures like (Filopodia, Lamellopodia - both are motility things).
4. Cleavage during cell division (cytokinesis).

Front 12

T/F. Microfilaments anchor some cytoplasmic proteins.

Back 12

True.

Front 13

What does ABP stand for?

How is ABP related to cell rigidity?

Back 13

Actin-Binding Protein.

ABPs are necessary for microfilaments to bundle and form a rigid structure.

Front 14

What three drugs interefere with the function of microfilaments?

Back 14

1. Cytochalasin
2. Phalloidin
3. Blebbstatin

Front 15

Name this disease:

You have a mutation in dystrophin, which is an ABP linking actin to plasma membrane.

What is the functional consequence of this mutation?

Back 15

Duchenne-Muscular Dystrophy (muscle wasting)

Without normal dystrophin, the cell membrane becomes weak or permeable so that extracellular components enter the cell and cause the muscle to explode and die.

Front 16

What is Duchenne Muscular Dystrophy?

Back 16

It's caused by a genetic defect in dystrophin. Dystrophin is an ABP. Without functional dystrophin, the cell membrane is weak, allowing extracellular components to enter the cell. The cell explodes and dies a fiery death.

Front 17

Describe a CFTR defect associated with the cytoskeleton.

Back 17

A mutation in CFTR causing Cystic Fibrosis prevents CFTR from interacting with actin.

Front 18

Describe Wiskott-Aldrich Syndrome.

Back 18

Wiskott-Aldrich Syndrome is an X-linked disease caused by eczema, thrombocytopenia (low platelet count), and immune deficiency.

It's caused by defects in actin nucleation and motility.

A nucleation site is where a bunch of actin molecules come from when they are needed.

Front 19

Name this disease.

an X-linked disease characterized by eczema, thrombocytopenia (low platelet count), and immune deficiency.

Back 19

Wiskott-Aldrich Syndrome.

Front 20

What cytoskeletal elements do Shigella and Listeria hijack?

Back 20

They hijack Actin and ABP cell elements.

Front 21

T/F. Can mutations in ABP cause deafness?

Back 21

True. Mutations in ABP can cause degeneration of stereocillia.

Front 22

T/F. Intermediate filaments have a consistent protein subunit.

Back 22

False. There are over 50 members of the intermediate filament family.

Front 23

Which cytoskeletal element is not essential for cell survival?

Back 23

Intermediate Filaments.

Front 24

Describe the assembly of intermediate filaments.

Back 24

It's complicated.

You get two intermediate filament proteins that join together as a coiled-coil homodimer. And then two dimers combine into tetramers, which align to form proto-filaments. They align in a staggered pattern.

It's not done yet.

Eight proto-filaments combine to form one intermediate filament. Which will most likely polymerize with other intermediate filaments.

Now it's done.

Front 25

Which cytoskeletal elements are relatively easy to disassemble? Which are relatively hard to disassemble?

Back 25

Microtubules and microfilaments are easier to disassemble than intermediate filaments.

Front 26

Where are intermediate filaments localized within a cell?

Back 26

They are found throughout the cytoplasm and in the nucleus, and they are particularly concentrated in a basket around the nucleus.

Front 27

What is the function of intermediate filaments in neurons? And what are they called in neurons?

Back 27

They are called neurofilaments and they fill and enlarge the axon, because the size determines the conductance velocity. (And overall coolness).

Front 28

Which cytoskeletal elements to Prickle Cells in the skin utilize for structure strength?

Back 28

Intermediate filaments.

Front 29

What are intermediate filaments in epithelial cells called?

What disease are they useful in diagnosing?

Back 29

They are called cytokeratins, and they are useful for diagnosing epithelial malignances/carcinomas.

Front 30

When Lamins and Vimentins polymerize to form what class of cytoskeletal element?

What role(s) do lamins and vimentins play?

Back 30

Intermediate filaments.

lamins are found on the inside of the nuclear membrane, and play a role in nuclear support (both structural and functional).

Vimentins are found on the nucleus, ER, and mitochondria. They provide flexibility and resilience and help anchor organelles.

Front 31

Describe the general structure of microtubules.

Back 31

The essential microtubule subunit is an alpha and beta subunit heterodimer. The heterodimers form a hollow tubule.

Front 32

Changes in what environmental factors cause assembly and disassembly of microtubules?

Back 32

[Ca2+] and temperature change lead to polymerization/depolymerization of microtubules.

Front 33

What does GTP addition to the end of a microtubule do?

Back 33

It stabilizes the microtubule and prevents further polymerization.

Front 34

Where are microtubules nucleated (concentrated in the cell)?

Back 34

At the MTOC (Microtubule Organizing Center), which is near the cell nucleus.

Front 35

What is dynamic instability of microtubules?

Back 35

It's the mechanism by which microtubules polymerize, which happens on the positive end.

Front 36

What proteins are associated with and regulate microtubules?

Back 36

Microtubule-Associated Proteins (MAPs)

Front 37

Which end of the microtubule is anchored at the end of the MTOC?

Back 37

The minus end.

Front 38

In what two mitotic structures are microtubules found?

Back 38

Centrioles and Mitotic spindle.

Front 39

What cytoskeletal element is found in centrioles and mitotic spindle?

Back 39

Microtubules

Front 40

In what two locomotion structures are microtubules found?

Back 40

Cilia and Flagella.

Front 41

Match these structures with their cytoskeletal elements.

Cilia
Microvilli
Filiopodia
Ruffles
Lamin
Flagella
Vimentin
Mitotic spindle

Back 41

Microfilaments:
Ruffles
Microvilli
Filiopodia

Intermediate filaments:
Vimentin
Lamin

Microtubules:
Mitotic spindle
Cilia
Flagella

Front 42

What cytoskeletal elements are used by Dyneins and Kinesins to move about?

Back 42

Both Dyneins and Kinesins use microtubules.

Front 43

What motor proteins use microtubules as a road?

Back 43

Dyneins and Kinesins use microtubules to move stuff about in cells.

Front 44

What proteins constitute occluding/tight junctions?

Back 44

claudin
occludin

Front 45

What is another name for occluding junctions?

Back 45

tight junctions

Front 46

Where are tight junctions found?

What function do they perform?

Back 46

Tight junctions are found, for example, in intestinal epithelia.

Tight junctions, also known as occluding junctions, serve to prevent diffusion of material from the apical end to the basal end between epithelial cells... i.e. tight junctions prevent material from flowing between cells from the lumen of the intestine to inside the body.

Front 47

What is the other name for adherens junctions?

Back 47

Zonula adherens

Front 48

Compare and contrast adherens junctions and desmosomes.

Back 48

Zonula adherens and desmosomes are both part of the cadherin family.

Desmosomes are spot junctions, and are anchored to the cytoskeleton by intermediate filaments.

Zonula adherens are belt junctions, and are anchored to the cytoskeleton by actin filaments.

Front 49

Compare and contrast focal adhesions and hemidesmosomes.

Back 49

Both Focal adhesions and hemidesmosomes are formed by proteins of the integrin family.

hemidesmosomes are like desmosomes except that hemiDs anchor cell-to-matrix instead of cell-to-cell. And they are anchored to the cytoskeleton by intermediate filaments.

Focal adhesions are anchored by actin, and transmit mechanical force and regulatory signals from the ECM to the cell, so that the cell can respond accordingly.

Front 50

Describe what homophilic binding and give two examples of proteins that exhibit homophilic binding. Are the examples Ca2+ or independent?

Back 50

Homophilic binding is when like-proteins bind cell-to-cell. Examples are Cadherins (mediated by Ca2+) and Immunoglobulins (Ca2+ independent).

Front 51

Describe what heterophilic binding is and give two examples of proteins that exhibit this.

Back 51

Heterophilic binding is when molecules of one kind (on a cell) bind to molecules of a different kind (on a different cell).

Selectin-to-Lectin interaction
MHC interaction with B- and T-cell receptors.

Front 52

What type of junction requires high [Ca2+]?

Back 52

Cadherins, which are cell-cell, and are found in Adherens junctions and desmosomes, require high [Ca2+] in order to form.

Front 53

What protein superfamily can mediate both homophilic and heterophilic interaction?

Back 53

Immunoglobulins

Front 54

What family of junctions is Ca2+ independent?

Back 54

Immunoglobulin.

Front 55

Are Selectins Ca2+ dependent or independent?

Back 55

Selectins are Ca2+ dependent.

Front 56

What cell-cell interaction can cause graft-vs-host rejection? Explain what cells are involved.

Back 56

Major Histocompatibility Complex (MHC) partakes in cell-to-B-cell and cell-to-T-cell interactions. Thus, if there is a compatibility issue between graft and host MHC and B-cells/T-cells, then rejection is possible.

Front 57

What fibrous proteins bridge ECM and cell surface proteins?

Back 57

Fibronectin and Laminin (NOT TO BE CONFUSED WITH LAMIN).

Front 58

Name the two proteins that will conduct a structure signal from the ECM to the cell interior.

Back 58

Fibronectin and Integrin couple together to perform this action.

Front 59

What proteins constitute a gap junction?

Back 59

6 Connexins form a connexon which constitutes a gap junction.

Front 60

What promotes an open gap junction pore?

Back 60

Low [Ca2+] and high pH promote an open gap junction.