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BIOL 1090 Final > Lecture 22 Motors, Actin, Cell Motility > Flashcards

Lecture 22 Motors, Actin, Cell Motility Flashcards

1
Q

MFs functions (5)

A
  • Maintenance of cell shape
  • Cell movement
  • Vesicle transport
  • Muscle contraction
  • Cytokinesis (contractile ring)
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1
Q

what are Microfilaments (MF)

A

the thinnest cytoskeletal element (~8 nm), Polymer of actin protein

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2
Q

Actin is the central component of MFs. It exists in cells either as a
______ (G-actin or globular actin) or as a _______
(F-actin or fibrous actin)

A

monomer, polymer

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3
Q

G-actin has four _______ and is divided by a ______ _____ creating two approximately equal-sized lobes

A

subdomains, central cleft

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4
Q

An actin filament (F-actin)
appears as two strands of ________ monomers. One F-actin unit has exactly 28 _______ of G-actin (14 in each strand), covering exactly a distance of
_______ __

A

G-actin, subunits, 72 nm

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5
Q

MFs are Dynamic like

A

MTs (Microfilaments have properties similar to microtubules)

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6
Q

F-actin filaments are polar they have a ____ and
____ end

A

plus, minus

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7
Q

Like microtubules, the ‘plus’ end ________/_______
quickly, while the ‘minus’ end assembles / disassembles _______.

A

assembles/disassembles, slowly

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8
Q

how are F-actin microfilaments arranged

A

in a loose array network
(meshwork) or tight bundles/cables/fibers

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9
Q

The organization of F-actin microfilaments is regulated by what

A

actin-binding proteins

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10
Q

Like microtubules, F-actin microfilaments are associated with what

A

motor
proteins

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11
Q

Myosins are a superfamily of ______ ______ associated with ________.
There is a large number of members in the myosin superfamily

A

motor proteins, microfilaments

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12
Q

Most myosin molecules move toward what end of microfilaments

A

the plus end

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13
Q

Conventional myosins characteristics

A
  • Type II
  • Primary motors for muscle contraction
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14
Q

Unconventional myosins characteristics

A
  • Type I and types III-XVIII
  • Organelle / vesicle movement
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15
Q

Unconventional myosins generate what

A

force and contribute to motility in non-
muscle cells

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16
Q

Actin-based protrusion of
leading edge (lamellipodium)
is powered by what

A

actin growth

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17
Q

Myosin-based
contraction pulls what forward

A

trailing edge

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18
Q

________-______ and ________-_______ motors can cooperate in
intracellular transport

A

Microtubule-based, microfilament-based

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19
Q

Kinesin transfers vesicle
to where

A

myosin motor protein

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20
Q

Movement of pigment
granules via the…

A

cytoskeleton

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21
Q

Intermediate Filaments (IF) characteristics (6)

A
  • Intermediate size (~10 nm diameter).
  • Exclusive to multicellular animal cells.
  • Provide structural support and mechanical strength.
  • Stable in comparison to MTs or microfilaments.
  • Arrangement of fibrous α-helical proteins.
  • Not polar (i.e. no ‘plus’ and ‘minus’ ends). IFs are not used for
    transport
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22
Q

Examples of IFs (3)

A
  • Keratins: epithelial cells
  • Neurofilaments: neuron-specific
  • Lamins: nucleus of cells
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23
Q

Intermediate filaments (neurofilaments) are especially abundant where

A

in the axons of neurons

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24
The Nucleus: Function (3)
1. Storage, replication, and repair of genetic material 2. Expression of genetic material 3. Ribosome biosynthesis
25
Expression of genetic material includes
* Transcription: mRNA, tRNA, rRNA * RNA splicing * Promoter region: control of transcription
26
what does cause? UV light exposure Replication errors Ionization radiation Cellular metabolism Chemical exposure
DNA damage thus DNA repair machinery
27
what encompasses these? * Nuclear membrane * Nuclear pores * Nuclear lamina
Nuclear envelope
28
what term encompasses these? * Chromatin * Nucleoplasm * Nucleolus
Nuclear content
29
the nuclear envelope has 2 parallel _______ ________ separated by 10-50nm space
phospholipid bilayers
30
what binds ribosomes and is continuous with rough endoplasmic reticulum
Outer nuclear membrane (ONM)
31
what has integral proteins and connects to nuclear lamina.
Inner nuclear membrane (INM)
32
the nuclear envelope: * Separates nuclear content from _____ * Separates _______ and _______ processes * Selective barrier that allows _______ ______ of molecules between nucleus and cytoplasm
cytoplasm transcription, translation Limited movement
33
what is The Nuclear Lamina
Thin meshwork of filamentous proteins that Supports the nuclear envelop
34
– Lamins (intermediate filaments) are found where?
in animal cells only.
35
Plants have ______ _____, but not made of lamin protein (we do not know what they are)
nuclear lamina
36
Nuclear lamina is bound to what
inner membrane of the nuclear envelop (NE) by integral membrane proteins
37
nuclear lamina Provides what for nuclear envelop
structural support and Attachment sites for chromatin (heterochromatin)
38
The nuclear lamina forms what next to the nucleoplasmic leaflet of the inner nuclear membrane
a meshwork
39
the nuclear pore is a ______ between cytoplasm and nucleus
gateway
40
how many pores/nucleus
3000-4000
41
nuclear pores are found where?
where inner and outer membranes fuses
42
nuclear Contains what... that involve the arrangement of different types of proteins
a complex protein structure
43
The nuclear pore complex (NPC) is composed of
nucleoporins (NUPs)—a large family of different proteins Octagonal symmetry Projects into cytoplasm and nucleoplasm
44
The NPC is what type of complex
supramolecular
45
the supramolecular complex is very big compared to what
a protein arrangement perspective
46
NPC is 15-30 times the size of a what
ribosome
47
Passive diffusion of molecules that are 40 kDA or less is
Rapid, 100 molecules/minute/pore
48
Regulated movement of larger molecules is
* Slow * 6 molecules/minute/pore
49
NLS = ?
several positively charged amino acids within the protein sequence
50
Regulated movement of proteins into the nucleus requires an intrinsic amino acid targeting sequence called what
Nuclear Localization Signal (NLS)
51
How does the NLS targets proteins to the nucleus: Protein with NLS (cargo) interacts with
Importin protein in cytoplasm
52
Cargo/Importin complex interacts with what
FG-NUPs at the NPC and enters the nucleoplasm
53
Ran-GTP (G-protein) interacts with what
Importin; cargo dissociates and stays in nucleoplasm
54
Ran-GTP/Importin complex exits nucleus through what
NPC nuclear pore complex
55
GTP hydrolysed to GDP. Importin is released in what
cytoplasm to find new cargo
56
Nuclear import and export are critical for what
cellular function
57
cellular function in terms of nuclear import/export includes
* Structural proteins (e.g. lamins) * DNA packaging proteins (e.g. histones) * Proteins for DNA replication, repair, and transcription * Proteins for RNA processing (splicing) and export * Proteins for ribosomes synthesis and export
58
the nucleolus is the largest structure inside what
the nucleus of eukaryotic cells and is NOT membrane-bound
59
Primary function of the nucleolus is what
biosynthesis of ribosomes
60
Ribosomes consist of two major components. describe them
the small ribosomal subunits, which read the RNA, and the large subunits, which join amino acids to form a polypeptide chain. Each subunit consists of one or more ribosomal RNA (rRNA) molecules and a variety of ribosomal proteins
61
Ribosome Biosynthesis includes (5) things
* Synthesis of ribosomal rRNAs * rRNA processing * Assembly of subunits— rRNA + ribosomal proteins * 40S and 60S subunits are exported to cytoplasm where they are assembled as 80S ribosomes * Ribosomal subunits are exported from the nucleus to cytoplasm

BIOL 1090 Final (10 decks)

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