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Histo Quiz 1 > Cell Structure 3 > Flashcards

Cell Structure 3 Flashcards

1
Q

What are the functions of the cytoskeleton?

A
  1. Mechanical support
  2. Motility (migration of cells, contraction, movement of organelles and materials w/in cell)
  3. Regulation of biochemical activity within the cell
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2
Q

What are the 3 parts of the cytoskeleton, in order of smallest to largest?

A
  1. Actin microfilaments
  2. Intermediate filaments
  3. Microtubules (25 nm)
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3
Q

What is the actin cortex?

A

A supporting layer of actin microfilaments underneath the plasma membrane of the cell. Provide a place where integral membrane proteins can be anchored.

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4
Q

What is anchored to intermediate filaments?

A

Desmosomes, which are anchored to desmosomes on adjacent cells.

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5
Q

What is the function of intermediate filaments?

A

Wrap and enclose nucleus and other parts of the cell so they stay in place; maintain spatial relationships in the cell. Provide tensile strength b/c anchored to cell wall.

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6
Q

Where do the microtubules originate from?

A

Centrosome a.k.a. microtubule organizing center (MTOC)

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7
Q

What is the function of microtubules?

A

Act as the highways along which materials and membrane-bound structures migrate within the cell.

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8
Q

Are microfilaments polar?

A

Yes, have a + and - side.

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9
Q

What is treadmilling, and what is it used for?

A

Addition of monomers to the + side of a microfilament and removal of monomers from the - side of the microfilament; used as a source of energy to do work for the cell.

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10
Q

What do microfilaments do?

A
  1. Make up cell actin cortex
  2. Responsible for maintaining cell shape (resist being extended, high tensile strength)
  3. Involved in cytoplasmic movements within the cell (streaming)
  4. Role in cell motility by forming and deforming and treadmilling
  5. Important in muscle contraction: associate w/ types of myosin to form contractile bundles
  6. Involved in cell division (forms cleavage ring)
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11
Q

What are the types of actin-binding proteins?

A
  1. Bundling: bundle actin together (e.g. into microvilli)
  2. Cross-linking: form a network of actin filaments (e.g. red blood cells)
  3. Filament-severing: cut actin filaments down to speed up breakdown
  4. Capping: add to + end to prevent dislocating of monomers and stabilize it.
  5. Motor: bind to actin filaments to slide over each other and can slide up and down filaments while dragging other organelles
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12
Q

What is the function of intermediate microfilaments?

A

For structure: maintenance of cell shape (distribute stress within the cell), anchoring of nucleus and other organelles, formation of nuclear lamina.

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13
Q

What is the nuclear lamina?

A

Support layer inside the nuclear envelope and provide points of attachment for chromatin (heterochromatin).

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14
Q

How do intermediate filaments provide mechanical support?

A

Distribute stress across large sheets of cells.

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15
Q

What happens in a blister?

A

Failure of intermediate filaments resulting in a break in the cell layer.

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16
Q

What is a Class I intermediate filament?

A

Made up of acidic and basic cytokeratins found in all epithelial cells

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17
Q

What is a Class II intermediate filament?

A

Made up of vimentin (found in cells of mesenchymal origin); desmin (found in muscle cells); glial fibrillary acidic protein (found in glial cells)

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18
Q

What is a Class III intermediate filament?

A

Made up of neurofilament proteins (found in neurons)

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19
Q

What is a Class IV intermediate filament?

A

Made up of nuclear lamins A, B, and C found in the nuclear lamina of all cells

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20
Q

What is the structure of the microtubules?

A

Long, straight, rigid cylinders formed by polymerization of alpha and beta tubulin dimers.

Polarized: have + and - end:
- end: embedded in MTOC
+ end: where depolymerization and polymerization occurs

21
Q

What is the function of microtubules?

A
  1. Cell shape (compression-resisting “girders”)
  2. Organelle movements (interact w/ molecular motors kinesin and dynein)
  3. Chromosome movements in cell division (form mitotic spindle)
  4. Cell motility (supporting structure of cilia and flagella)
22
Q

What is dynamic instability with regards to microtubules?

A

Ability to grow rapidly and shrink rapidly based on the GTP abundance. Both growth and shrinkage occurs at the + end.

23
Q

What are the 2 molecular motors that microtubules are a substrate for?

A
  1. Kinesin (moves anterograde: - to +)

2. Dynein (moves retrograde: + to -)

24
Q

What are kynesin and dynein?

A

ATPases involved in transport of membrane-bound organelles (mitochondria, secretory vesicles): in presence of ATP, undergo conformational changes that cause “feet” to move along microtubules.

25
Q

What are the 3 types of specialized cell wall membranes?

A
  1. Apical
  2. Lateral
  3. Basal
26
Q

What is the purpose of microvilli, and which side are they located on?

A

To increase surface area for absorption; apical.

27
Q

How are microtubules organized in cilia?

A

9 doublet microtubules around the perimeter and a pair of singles in the center. Each doublet pair has a dynein arm reaching out to next doublet that tries to pull microtubules one over another.

28
Q

To what are cilia anchored?

A

Basal body embedded in terminal web.

29
Q

What is the purpose of cilia, and are they motile?

A

To move fluids over the cell surface; yes: dynein-dependent.

30
Q

What is the difference between microvilli and cilia?

A

Microvilli are non-motile and made of actin filaments; cilia are motile (dynein) and made of microtubules.

31
Q

What are the 3 types of junctions on the lateral surface of the cell?

A
  1. Tight (zonula occludens) junctions
  2. Anchoring junctions
  3. Gap (nexus) junctions
32
Q

What are the 2 proteins that fuse cell membranes together in tight junctions?

A

occludin and claudin

33
Q

What do tight junctions do?

A

Prevent passage of water-soluble molecules between adjacent cells and prevents movement of integral membrane proteins from cell surface.

34
Q

How do adherens junctions work?

A

Hydrophilic (calcium-dependent) adhesive interactions mediated by cadherin proteins between adjacent cells.

35
Q

What are adherens junctions made up of?

A

Actin filaments

36
Q

How do desmosomes work?

A

Proteins within the cell that connect lateral surface of cell interior to the terminal web. Anchors terminal web to cell membrane: points of adhesion via hydrophilic interactions. Point where stresses can be shared through all populations of cells.

37
Q

What are desmosomes made up of?

A

Intermediate filaments

38
Q

What is the purpose of a gap junction?

A

To form communicating junctions between cells:

  • allow passage of ions and small molecules between adjacent cells
  • couple cells electrically and metabolically
39
Q

What is a connexon?

A

6 proteins arranged around a central aqueous pore that traverses adjacent cell membranes.

40
Q

How are cells anchored to a basement membrane?

A

Hemidesmosomes: half a desmosome that anchors cell to extracellular matrix

41
Q

What are the parts of the basement membrane?

A
  1. Basal lamina (lamina lucida and lamina densa)
  2. Reticular fibers
  3. Anchoring fibrils and plaque
42
Q

What are the components of the basement membrane?

A

Laminin, type IV collagin, entactin, perlecan

43
Q

What does the basement membrane do?

A

Supports the cell, supplies points of adhesion of cell to extracellular matrix, helps with filtration.

44
Q

What are focal contacts?

A

Contacts between the cell and extracellular matrix compartment

45
Q

What are focal contacts mediated by?

A

Integrins: transmembrane proteins w/ alpha and beta subunits.

46
Q

What do integrins do?

A

Mediate adhesion to extracellular matrix.

Help w/ signal transduction: can signal and cause changes in actin cytoskeleton.

47
Q

What happens in Pemphigus disease?

A

Autoimmune disease directed against components of desmosome and hemidesmosome. Results in epidermal blistering and loss of extracellular fluids.

48
Q

What happens in Alport’s Syndrome?

A

Inherited defecit in structure of Type IV collagen (part of basement membrane/filtration structure). Results in blood in urine.

49
Q

How is cell adhesion related to cancer?

A

Cancer mutates/alters expression of various cell adhesion genes, resulting in metastasis where cells don’t stay put.

Histo Quiz 1 (6 decks)

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