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Histology > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

List and differentiate the 3 types of Cytoskeleton Components

A
  1. Microfilaments (Actin) (7nm) 2. Intermediate Filaments (10nm) 3. Microtubules (25nm)
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2
Q

List Characteristics of Actin Monomers and Filaments

A

Highly Conserved among Eukaryotes. Up to 7um long Organized into 3D Networks/Bundles Directly/Indirectly bind to specific transmembrane proteins Exist as Monomers (G-Actin) and Long-chains (F-Actin)

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3
Q

What are the varieties of Actin Monomers and Filaments

A

Alpha-Actin for muscle tissue

Beta-Actin & Gamma-Actin for non-muscles

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4
Q

What is Treadmilling?

A

Dynamic balance between the polymerizing (growing end) and the depolymerizing (disassembly) ends to maintain actin-filament length.

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5
Q

What is the fist step in Actin Polymerization?

A

Trimer is formed

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6
Q

Actin-Polymerization is either reversible or non-reversible process?

A

Reversible

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7
Q

What is the +/Barbed end?

A

Growing end where ATP is hydrolyzed into ADP

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8
Q

What does Very Low concentrations of G-Actin favor?

A

Disassembly of Actin-Filaments.

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9
Q

What does Cytochalasin do?

A

Binds to +/Barbed End and block elongation which inhibits cell movements (cell division)

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10
Q

What does Phalloidin do?

A

Bind to Actin-Filaments and prevents dissociation and can be labeled with Fluorescent Dyes to give visualization of Actin-Filaments.

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11
Q

What does Spectrin do?

A

In RBCs and binds to cortical cytoskeleton to the plasma-membrane.

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12
Q

What does Dystrophin do?

A

Binds to cortical-cytoskeleton to the plasma-membrane in Microvilli.

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13
Q

What does Calmodulin & Myosin I do?

A

Cross-links Actin to plasma membrane in microvilli.

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14
Q

What does Alpha-Actinin do?

A

Cross-links stress fibers & connects Actin to Protein-Plasma membrane complexes.

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15
Q

What does Filamin Do?

A

Cross links Actin at WIDE angles to form screen like gels.

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16
Q

What does Thymosin do?

A

Captures and Organizes Actin G-monomers into a pool in cells.

17
Q

What does Profilin do?

A

Promotes F-Actin growth at the +/Barbed End, and prevents nucleation of G-actin.

18
Q

What does Gelsolin do?

A

1st. it is a Capping protein that prevents the loss and addition of Actin-Monomers. 2nd. it is a severing Protein when in the presence of Calcium it is bound the +/Barbed end and prevents further filament growth.

19
Q

What does ARP2/3 do?

A

Starts the assembly of F-actin filaments on the side of an existing filament which promotes branching.

20
Q

What does Latrunuclins do?

A

Binds to G-actin and induces F-Actin depolymerization

21
Q

Describe the Basic Structure and assembly of Intermediate Filaments.

A

a. 8-10nm thick and provide structural support b. Provide tensile strength in cells like neurons/muscle c. Strengthen desmosomes and Hemidesmosomes. d. Form a cytoplasmic network in most cells. e. Associate with other cytoskeletal elements to form a scaffolding that organizes the internal structure of the cell. f. Central rod of polypeptides forms a coiled dimer i. Rods are aligned tail-to-tail and head-to-head g. Dimers are in a staggered antiparallel fashion to form tetramers i. B/c of the antiparallel association of the dimers, polymerized filaments do NOT have distinct ends ii. Therefore, they are more stable than actin and do NOT demonstrate dynamic behaviors such as Treadmilling iii. CANNOT tell the difference between one end or the other because NOT polar.

22
Q

Describe the structure of a Microtubule

A

a. 25um in diameter b. Made of tubulin dimers: Alpha unit + Beta unit c. 13 protofilaments arranged in parallel fashion to form a cylinder with a hollow core. d. Have fast growing “+ end”, and slow growing “– end”

23
Q

Relate the processes of Treadmilling and Dynamic Instability to Microtubule Assembly and Disassembly

A

a. Tubulin dimers with GTP bound to the Beta-tubulin are part of the growing end. b. Positive End: Grows faster than minus end in presence of LOW Calcium concentration c. After polymerization, GTP is hydrolyzed to GDP, and the tubulin is less stable and dimers at the minus end dissociate. d. High concentration of Tubulin-GTP, the dimers are added more rapidly than GTP is hydrolyzed, and the microtubule grows. e. If tubulin-GTP drops, GTP at the plus end is hydrolyzed and dimers are lost.

24
Q

List functions of Cytoskeleton

A

a. Cell movement b. Support/Strength for the cell c. Phagocytosis d. Mitotic spindle formation e. Cytokinesis f. Cell-to-Cell and cell-extracellular matrix adherence g. Changes in cell shape

25
Q

Describe the role of Microtubules in Mitosis

A

Major component of mitotic spindle.

26
Q

Describe the mechanism of Intraciliary Transport

A

a. Particles are mobilized by Kinesin & Cytoplasmic Dynein along the Microtubule doublets of the Axoneme. b. Defective transport can lead to abnormal development of cilia and flagella

27
Q

Describe the role of Microtubules and Motor proteins in Axonal Transport

A

a. Bundles of Microtubules form tracks within the Axon to carry vesicles (that hold neurotransmitters like Ach). b. Motor Proteins Kinesin and Cytoplasmic Dynein transport the vesicles.

28
Q

Describe the # of Heads, Tail binds to, Heads binds to, and Direction of head motion for Myosin I

A

One Heads Tail binds to cell membrane Head binds to actin Moves to Plus end

29
Q

Describe the # of Heads, Tail binds to, Heads binds to, and Direction of head motion for Myosin II

A

Two heads Tail binds to Myosin II Heads binds to Actin Plus end

30
Q

Describe the # of Heads, Tail binds to, Heads binds to, and Direction of head motion for Kinesin

A

Two Heads Tail Binds Vesicle Head binds to Microtubule Direction is Plus end

31
Q

Describe the # of Heads, Tail binds to, Heads binds to, and Direction of head motion for Dynein

A

Two heads Tail binds to Vesicle Head binds to Microtubule Minus End

Histology (12 decks)

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