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BMSC > Lecture 13 > Flashcards

Lecture 13 Flashcards

1
Q

What 3 filament structures is the cytoskeleton composed of?

A

Microtubules
Actin filaments
Intermediate filaments

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2
Q

What are some properties of Intermediate filaments?

A

strong, flexible, ropelike
provides mechanical strength against physical stress

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3
Q

What protein do intermediate filaments use to connect to other filaments?

A

Plectin

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4
Q

what is the architecture order of Intermediate filaments?

A

Monomers -> dimers -> tetramer ->filament unit

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5
Q

True or false?
Intermediate filaments require ATP and/or GTP?

A

False

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6
Q

What controls assembly and disassembly of Intermediate filaments?

A

phosphorylation and Dephosphorylation

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7
Q

What are 2 types of Intermediate filaments?

A

Keratin containing and Neurofilaments

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8
Q

what and where are keratin containing filaments commonly found? what are they commonly attached to?

A

Structural proteins of epithelial cells
commonly attached to nuclear envelope

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9
Q

Where are Neurofilaments commonly located? how are they orientated?

A

in the cytoplasm of the neurons
orientated parallel to the axon

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10
Q

What is actin structures involved in?

A

intracellular motile processes

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11
Q

what 3 ways can actin filaments be organized in?

A

Ordered arrays
highly branched networks
tightly anchored bundles

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12
Q

True or false?
Actin filaments are not a major contractile muscle protein?

A

False, they are a major contractile protein

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13
Q

True or false?
Actin is a major protein in every eukaryotic cell?

A

True, they are

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14
Q

how is actin filaments assembled and disassembled?

A

ATP binds to Actin resulting in the filament length increasing
will keep increasing until ATP conc. decreases
will begin ‘treadmilling’ once reaction on both ends remains constant

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15
Q

What can influence Actin filament assembly / disassembly rates? why is this required?

A

a number of different proteins
Required for cell locomotion, change in cell size, phagocytosis, cytokinesis

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16
Q

What is a molecular motor than operates with actin filaments?

A

Myosin motors

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17
Q

What direction do Myosin motors move in?

A

Towards the ‘barbed’ end of the actin filament

18
Q

What characteristic do all myosins share? what 2 binding sites are there?

A

A motor head
a binding site for the actin filament
a binding site for ATP consumption to drive the motor

19
Q

where on myosin motors do varieties occur?

A

the tail portions of the molecule

20
Q

What are the 2 types of Myosin motors?

A

Conventional (Type II) and unconventional

21
Q

What are Conventional motors commonly used for?

A

muscle contraction
splitting of cell during division
generating tension at focal adhesions
cell migration
turning behavior at growth cones

22
Q

What is the structure of Conventional Myosins?

A

pair of heads
pair of necks
2 light chains
2 intertwined long heavy chains

23
Q

In what direction do myosin molecules assemble on filaments?

A

with the tails pointed towards the center and the heads pointed away from the center

24
Q

Why is the bipolar center of a filament important for myosin heads?

A

so the heads on opposite ends of the filament have the ability to pull actin filaments towards one another

25
Q

In what way to unconventional myosins move? What molecule is it similar to?

A

“hand-over-hand” - one of the 2 heads must be bound at all times to a polarized track
(similar to kinesin)

26
Q

True or False?
Skeletal muscle fibers are uni-nucleated cells

A

False, they are multi-nucleated

27
Q

what strands do each muscle fiber contain?

A

myofibrils

28
Q

what are the contractile units in myofibrils?

A

sarcomeres - repeating linear array of contractile units

29
Q

How are sarcomeres organized?

A

Unit screeches from Z-line to Z-line
Dense middle region (H zone / A band)
I band (thin filaments only)
H zone (thick filaments only)
A band region (excluding H-zone) is where thin and thick filaments overlap

30
Q

How do the regions change during muscle contraction in a sarcomere?

A

H (thick filaments) and I band (thin filaments) decrease as the filaments regions overlap each other through Actin-movement
Z lines (edge of the unit) move inward towards edge of A-band

31
Q

What 3 things to thin filaments contain?

A

Actin, tropomyosin and troponin

32
Q

What is Troponin?

A

protein complex that contacts both actin and tropomyosin

33
Q

What is tropomyosin?

A

molecule that fits securely into thin filament (interacts with 7 actin units)

34
Q

How do myosin heads engage with filaments during contraction? what is it similar to?

A

each myosin head binds to a thin filament
when bound, a conformational change occurs that moves the thin actin filament
all the myosin heads act in sync in a continuous motion

35
Q

what determines the behavior and organization of actin filaments inside cells?

A

integrations with actin binding proteins determine the organization and behavior

36
Q

what are the 9 categories actin binding proteins can be divided into based on function?

A

Nucleating
Monomer-sequestering
End-blocking
monomer-polymerizing
Actin filament depolymerizing
cross-linking
filament-severing
membrane binding

37
Q

What are some activities where cell locomotion is important?

A

Tissue / organ development
formation of blood vessels
development of axons
wound healing
protection against infection

38
Q

what is the fibroblast locomotion leading edge called?

A

Lamellipodium

39
Q

What is a growth cone?

A

A highly motile region of the cell that explores the environment

40
Q

Describe the structure and functions of intermediate filaments.
▪ Explain the structure and function of actin and myosin and how
they interact.
▪ Describe the molecular components of muscle.

A

BMSC (22 decks)

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