Cytoskeleton

Question 1

Due to Abnormal Ciliary Dynein

• Symptoms include:
  
  • Respiratory system abnormalities
  • Situs Inversus
    
    • Thoracic& abdominal organs on the wrong side of the body.

Answer 1

Kartagener’s Syndrome

Question 2

Cell interior composed of:

Answer 2

• Cytoskeleton
• Cytosol
• Organelles

Question 3

Cytosol often comprises more than ______% of a cell’s volume.

Site of ______

Answer 3

50%; protein synthesis

Question 4

Elements of the Cytoskeleton

Answer 4

• Microfilaments (Actin, “thin filaments”) (6 types)
• Microtubules (Tubulin) (12 types)
• Intermediate filaments (31 types)
• Motor proteins. i.e. Myosins, Dynein, Kinesin.

Question 5

Answer 5

Question 6

Answer 6

Question 7

The most abundant protein in most eukaryotic cells

Answer 7

Microfilaments

Question 8

Main component of microfilaments, which are double-stranded, thin, and flexible structures

Answer 8

Actin

Question 9

Most actin molecules work together to give support and structure to the plasma membrane and are found

Answer 9

near the cell membrane

Question 10

Microfilaments are composed _________ , and generate force by ________, causing movement of the intervening strand.

Answer 10

of linear polymers of actin subunits; elongation at one end of the filament coupled with shrinkage at the other

Question 11

Actin structures are controlled by the

Answer 11

Rho family of small GTP - binding protein:

• Rho itself for contractile acto-myosin filaments (“stress fibers”)
• Rac for lamellipodia
• Cdc42 for filopodia.

Question 12

Microvilli contain

Answer 12

actin

Question 13

Microvilli

Answer 13

Question 14

Microtubules

Answer 14

• Long, hollow, cylindrical structures composed of tubulin and organized around a centrosome, an organelle usually found in the center of the cell near the cell nucleus.
  
  • One end of each microtubule is embedded in the centrosome; the microtubule grows outward from there.

Question 15

Microtubules are much more rigid than _______ molecules and have a larger diameter: _______ nanometers

They are _________ and go through a process of continuous growth and decay.

Answer 15

actin molecules; 25 nanometers

relatively unstable

Question 16

Microtubules play key roles in:

Answer 16

• intracellular transport (associated with dyneins and kinesins, they transport organells like mitochondria or vesicles)
• the axoneme of cilia and flagella
• the mitotic spindle
• syntheis of the cell wall in plants

Question 17

Molecules that bind to microtubules

Answer 17

1. Colchicine (depresses MT assembly) (avidly taken up by neutrophils, which become suppressed as a treatment for gout)
2. Tau (abnormal in Alzheimer’s disease)
3. Motor proteins
   
   1. Dynein (moves to minus end, center)
   2. Kinesin (moves to plus end, outer)

Question 18

Moves towards minus end (center)

Answer 18

Dynein

Question 19

Kinesin moves towards ______ end (outer)

Answer 19

plus

Question 20

Distribution of Cytoplasmic MT’s goes from ______ end to ______ ends

Answer 20

Minus ends (internal) to plus ends (outward)

Question 21

Ciliated epithelium contains

Answer 21

microtubulues

Question 22

Microtubules in cilia and flagella

Answer 22

Axoneme

Question 23

The Axonenme structure

Answer 23

(9 doubletes + 2 MT’s)

Question 24

Kartagener’s Syndrome

Answer 24

• Due to abnormal Cilary Dynein
• Symptoms
  
  • Respiratory system abnormalities
  • Situs Inversus
  • Thoracic & abdominal organs are on the wrong side of the body
• Reason: Ciliary moverment aids organogenesis in the early embryo

Question 25

Primary (sensory) cilia are found in many cells:

Answer 25

* Neurons * Chondrocytes * kidney epithelium, etc.) Receptors for neurotransmitters and many other molecules localize to cilia

Question 26

Disruption of the sensory functions of cilia is found in a genetic disorder,

Answer 26

Bardet-Biedl syndrome

Question 27

CNS Neurons commonly have how many cilia?

Answer 27

a single cilium

Question 28

\_\_\_\_\_ centrioles make a centrosome

Answer 28

2 centrioles make a centrosome Triplet of microtubules

Question 29

Microtubules attach to chromosomes \_\_\_\_\_\_\_

Answer 29

kinetochores

Question 30

Rope-like and fibrous, with a diameter of approximately 10 nanometers

Answer 30

Intermediate filaments These filaments extend through the cytosol and help to resist stress and increase cellular stability.

Question 31

Intermediate filaments that form a network surrounding the nucleus

Answer 31

nuclear lamina

Question 32

Intermediate filaments maintain cell-shape by

Answer 32

bearing tension (microtubules, by contrast, resist compression) micro and intermediate filaments- cables microtubules - cellular support beams.

Question 33

Intermediate filaments organize the internal tridimensional structure of the cell by:

Answer 33

* anchoring organelles * serving as structural components of the nuclear lamina and sarcomeres Participate in some cell-cell and cell-matrix junctions

Question 34

Different intermediate filaments are:

Answer 34

* Keratins: in epithelial cells * Desmin: in muscle cells * Vimentin: in connective tissue cells * Neurofilaments: in nerve cells * GFAP: Glial Fibrillary Acidic Protein of Astrocytes * Lamins: in all cell types: govern shape of nucleus and interconnects nuclear pores

Question 35

Myosin

Answer 35

* A family of ATP-dependent motor proteins involved in muscle contraction and in a wide range of motility processes. * Responsible for actin-based motility. A large number of genes have been discovered.

Question 36

Myosin was originally thought to be restricted to muscle cells (hence, "myo"), but there is no single "myosin" but rather a huge superfamily of genes whose protein products share the basic properties of:

Answer 36

* Actin binding * ATP hydrolysis (ATPase enzyme activity) * Force transduction

Question 37

Virtually all eukaryotic cells contain myosin isoforms. Some isoforms have \_\_\_\_\_\_\_\_\_, while other isoforms are \_\_\_\_\_\_.

Answer 37

specialized functions in certain cell types (such as muscle); ubiquitous

Question 38

Myosin structure

Answer 38

* Head domain * Neck domain * Tail domain

Question 39

Domain that binds actin, and uses ATP hydrolysis to generate force and to "walk" along the filament towards the barbed (+) end * (with the exception of myosin VI, which moves towards the pointed (-) end).

Answer 39

Head domain

Question 40

Domain that acts as a linker and as a lever arm for transducing force generated by the catalytic motor domain. Also serve as a binding site for myosin light chain which are distinct proteins that form part of a macromolecular complex and have regulatory functions.

Answer 40

Neck domain

Question 41

Answer 41

Myosin I

Question 42

Answer 42

Myosin II

Question 43

Answer 43

Question 44

Myosin, Actin, & Cell Movement

Answer 44