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Molecular Exam 2 > White lecture 1 9/21 > Flashcards

White lecture 1 9/21 Flashcards

1
Q

What is the significance of the cytoskeleton?

A
  • bones of the cell
  • helps to organize
  • correctly shaped cells
  • insures proper structure
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2
Q

True or false, the cytoskeleton can move the cell

A

True, usually via crawling

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3
Q

What does the cytoskeleton help to do in cell division?

A

Helps to pull the chromosomes apart

Also helps to split the dividing cells apart

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4
Q

What happens if there is defect in the cytoskeleton in regards to cell division?

A

Abnormal number of chromosomes as it helps to pull them apart
incorrect cell division

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5
Q

What is the role of the cytoskeleton in regards to intracellular trafficking?

A

Sidewalk; vesicles are able to move around the cytoskeleton like a sidewalk

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6
Q

What is the importance of the cytoskeleton to sperm?

A

acts like a motor

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7
Q

Which cells need to crawl?

A

WBC and fibroblasts

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8
Q

What is responsible for the biconcavity of the RBC?

A

cytoskeleton

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9
Q

Describe why a cytoskeleton is important to RBC’s

A
  • biconcavity
  • strength
  • flexibility and strength in transport
  • withstand shearing force of the heart
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10
Q

What happens if the cytoskeleton in RBC’s is out of whack?

A

-anemia
-hereditary spherocytosis
hemolytic anemia

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11
Q

Describe Hereditary spherocytosis

A

RBCs are spherical and fragile

and they burst

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12
Q

Define protofilaments

A

long linear strings of proteins of subunits joined end to end
thermally unstable

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13
Q

How is a cytoskeletal filament able to resist breakage by ambient thermal conditions?

A

There is strength in numbers, the protofilaments bind side to side. THEREFORE when it is trying to be broken, 5 of the bonds need to be broken

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14
Q

What are the three families of cytoskeletal proteins?

A

actin filaments
microtubules
intermediate filaments

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15
Q

Describe an actin filament

A
  • two stranded helical polymers
  • subunits are compact and globular flexible 5-9 nm in diameter
  • mardi gras beads
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16
Q

What is the function of the actin filaments?

A

determine the shape of a cell’s surface and are necessary for whole-cell locomotion, secretion, and endocytosis

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17
Q

Describe microtubules

A
  • slinky of life
  • tube like structures
  • long hollow cylinders
  • tubulin subunits that are compact and globular
  • long and straight 25 nm
  • rigid
  • one end attached to a singe microtubule-organizing called a centrosome
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18
Q

What is the function of the microtubule?

A
  • determine the position of the membrane enclosed organelles
  • directs intracellular transport
  • make up centrioles and mitotic spindles
  • sperm swim and cilia moves eggs
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19
Q

What is lacking in function in cystic fibrosis?

A

Cilia

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20
Q

Describe intermediate filaments

A
  • rope like fibers
  • large heterogeneous family
  • smaller subunits that are elongated and fibrous
  • across the cytoplasm to provide strength
  • one cell junction to another
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21
Q

What is the function of the intermediate filaments?

A
  • provide mechanical strength
  • strong filament
  • resists mechanical stress
  • formation of hair and finger nails
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22
Q

How are intermediate filaments organized to allow it to tolerate bending and stretching?

A

staggered side to side, rope-like structures

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23
Q

Describe the adaptive nature of a fibroblast actin specifically in the division of cells

A
  • actin cytoskeleton assembles to push its leading edge which allows the fibroblast to crawl
  • actin can disassemble so that the cell can change shape
  • actin forms a contractile ring and allows cell division
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24
Q

Describe the adaptive nature of fibroblast microtubules specifically in the division of cells

A
  • microtubules emanate from a single microtubule-organizing center
  • form a bi-polar mitotic spindle
  • separates chromosomes
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25
What are some examples of the stable structures that the cytoskeleton helps to form?
- intestinal cells | - hair cells in the ear
26
Describe the intestinal cells: 1. What allows the structure? 2. Define microvilli and their uses? 3. polarity
1. actin filaments determines the structure 2. microvilli are projections that stick off of the cell like fingers, QUADruple the surface area and increase the absorption rate 3. Polarity maintained via actin, intermediate, and microtubules; apical surface absorbs the nutrients and the basolateral surface is where the cells transfer the nutrients to the blood stream
27
What are the building blocks of the cytoskeleton?
protein subunits
28
What interactions hold together the cytoskeletal filaments?
weak non-covalent interactions for rapid assembly and disassembly
29
Describe the formation of actin
- Actin subunits form filaments (monomer has a binding site for ATP) - helical- twist around each other in a right handed helix - arranged head to tail and generate polarity - flexible and easily bent
30
What happens at the positive end of the actin filament?
fast growing or fast shrinking end
31
What happens at the negative end of the actin filament?
slow growing or slow shrinking end
32
What is the function of ATP actin?
polymerizes
33
What is the function of ADP actin?
disassembles
34
What is tubulin?
subunit of a microtubule; alpha and beta tubulin with binding sites for GTP
35
Describe the binding of the tubulin
-The top beta tubulin binds to the bottom alpha tubulin forms positive and negative ends -stiff hollow tube with alternating subunits with multiple contacts that makes the structure stiff
36
Define polymerization
assembly of actin or tubulin subunits into a linear polymer
37
Define depolymerization
removal of the monomers at the ends of the polymer
38
Define nucleation
subunits must assemble into initial aggregate or nucleus which allows for a large filament to form rate limiting step in cytoskeletal formation
39
Define filament elongation
growth phase; subunits are quickly added onto the ends of the nucleated filaments
40
Define the steady state of the formation of the cytoskeleton
the equilibrium phase | rate of monomer addition equals the rate of the monomer loss
41
What are the 3 phases of the formation of the cytoskeleton?
1. nucleation (rate limiting) 2. filament elongation 3. steady state
42
What is the T form of the actin and tubulin molecules?
ATP/GTP bound
43
What is the D form of the actin and tubulin molecules?
ADP/GDP bound
44
When does the molecule transition from the T to the D form?
After it is assembled into a polymer
45
What form (T or D) is the tip of polymer in?
T form
46
What form (T or D) is the positive end of the polymer in?
T formation
47
What form (T or D) is the negative end of the polymer in?
D formation
48
Which end are the subunits added to?
added to the positive end and removed at the negative end
49
Describe treadmilling
the positive end grows while the negative end shrinks' escalator effect
50
Which filament does the tread milling predominate in?
Actin filaments
51
Define catastrophe
change from the growth to rapid shrinkage
52
Define rescue
change from rapid shrinkage to growth
53
Define dynamic instability
The change from rescue to catastrophe
54
Describe the structure of the filament after the tubulin GTP is added
It remains straight
55
Describe what happens to the structure of the protofilament after GTP hydrolysis
protofilaments curve which makes polymerization easier
56
In which filament does dynamic instability predominate?
microtubules
57
How does a pair of dimer intermediates align?
in an antiparallel manner, to form a staggered tetramer
58
How many tetramers pack together laterally to form a microfilament?
eight parallel tetramers
59
What is the most diverse type of intermediate filaments?
keratins
60
Define accessory proteins and briefly how they help in a cell
- includes motor proteins that convert ATP into mechanical movement - move organelles along filaments - move filaments themselves

Molecular Exam 2 (13 decks)

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