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M1 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

Due to Abnormal Ciliary Dynein

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

Kartagener’s Syndrome

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2
Q

Cell interior composed of:

A
  • Cytoskeleton
  • Cytosol
  • Organelles
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3
Q

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

Site of ______

A

50%; protein synthesis

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4
Q

Elements of the Cytoskeleton

A
  • Microfilaments (Actin, “thin filaments”) (6 types)
  • Microtubules (Tubulin) (12 types)
  • Intermediate filaments (31 types)
  • Motor proteins. i.e. Myosins, Dynein, Kinesin.
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5
Q
A
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6
Q
A
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7
Q

The most abundant protein in most eukaryotic cells

A

Microfilaments

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8
Q

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

A

Actin

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9
Q

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

A

near the cell membrane

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10
Q

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

A

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

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11
Q

Actin structures are controlled by the

A

Rho family of small GTP - binding protein:

  • Rho itself for contractile acto-myosin filaments (“stress fibers”)
  • Rac for lamellipodia
  • Cdc42 for filopodia.
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12
Q

Microvilli contain

A

actin

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13
Q

Microvilli

A
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14
Q

Microtubules

A
  • 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.
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15
Q

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.

A

actin molecules; 25 nanometers

relatively unstable

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16
Q

Microtubules play key roles in:

A
  • 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
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17
Q

Molecules that bind to microtubules

A
  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)
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18
Q

Moves towards minus end (center)

A

Dynein

19
Q

Kinesin moves towards ______ end (outer)

A

plus

20
Q

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

A

Minus ends (internal) to plus ends (outward)

21
Q

Ciliated epithelium contains

A

microtubulues

22
Q

Microtubules in cilia and flagella

A

Axoneme

23
Q

The Axonenme structure

A

(9 doubletes + 2 MT’s)

24
Q

Kartagener’s Syndrome

A
  • 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
25
Q

Primary (sensory) cilia are found in many cells:

A
  • Neurons
  • Chondrocytes
  • kidney epithelium, etc.)

Receptors for neurotransmitters and many other molecules localize to cilia

26
Q

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

A

Bardet-Biedl syndrome

27
Q

CNS Neurons commonly have how many cilia?

A

a single cilium

28
Q

_____ centrioles make a centrosome

A

2 centrioles make a centrosome

Triplet of microtubules

29
Q

Microtubules attach to chromosomes _______

A

kinetochores

30
Q

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

A

Intermediate filaments

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

31
Q

Intermediate filaments that form a network surrounding the nucleus

A

nuclear lamina

32
Q

Intermediate filaments maintain cell-shape by

A

bearing tension (microtubules, by contrast, resist compression)

micro and intermediate filaments- cables

microtubules - cellular support beams.

33
Q

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

A
  • anchoring organelles
  • serving as structural components of the nuclear lamina and sarcomeres

Participate in some cell-cell and cell-matrix junctions

34
Q

Different intermediate filaments are:

A
  • 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
35
Q

Myosin

A
  • 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.

36
Q

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:

A
  • Actin binding
  • ATP hydrolysis (ATPase enzyme activity)
  • Force transduction
37
Q

Virtually all eukaryotic cells contain myosin isoforms. Some isoforms have _________, while other isoforms are ______.

A

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

38
Q

Myosin structure

A
  • Head domain
  • Neck domain
  • Tail domain
39
Q

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).
A

Head domain

40
Q

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.

A

Neck domain

41
Q
A

Myosin I

42
Q
A

Myosin II

43
Q
A
44
Q

Myosin, Actin, & Cell Movement

A

M1 (48 decks)

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