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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
Q

The Nucleus: Function (3)

A
  1. Storage, replication, and repair of genetic material
  2. Expression of genetic material
  3. Ribosome biosynthesis
25
Q

Expression of genetic material includes

A
  • Transcription: mRNA, tRNA, rRNA
  • RNA splicing
  • Promoter region: control of transcription
26
Q

what does cause?

UV light exposure Replication errors
Ionization radiation
Cellular metabolism
Chemical exposure

A

DNA damage thus DNA repair machinery

27
Q

what encompasses these?

  • Nuclear membrane
  • Nuclear pores
  • Nuclear lamina
A

Nuclear envelope

28
Q

what term encompasses these?

  • Chromatin
  • Nucleoplasm
  • Nucleolus
A

Nuclear content

29
Q

the nuclear envelope has 2 parallel _______ ________ separated by 10-50nm space

A

phospholipid bilayers

30
Q

what binds ribosomes and is continuous with rough endoplasmic reticulum

A

Outer nuclear membrane (ONM)

31
Q

what has integral proteins and connects to nuclear lamina.

A

Inner nuclear membrane (INM)

32
Q

the nuclear envelope:

  • Separates nuclear content from _____
  • Separates _______
    and _______ processes
  • Selective barrier that
    allows _______ ______
    of molecules between
    nucleus and cytoplasm
A

cytoplasm

transcription, translation

Limited movement

33
Q

what is The Nuclear Lamina

A

Thin meshwork of filamentous proteins that Supports the nuclear envelop

34
Q

– Lamins (intermediate filaments) are found where?

A

in animal cells only.

35
Q

Plants have ______ _____, but not made of lamin protein (we do not know what they are)

A

nuclear lamina

36
Q

Nuclear lamina is bound to what

A

inner membrane of the nuclear envelop (NE) by integral membrane proteins

37
Q

nuclear lamina Provides what for nuclear envelop

A

structural support and Attachment sites for chromatin (heterochromatin)

38
Q

The nuclear lamina forms what next to the
nucleoplasmic leaflet of the inner nuclear membrane

A

a meshwork

39
Q

the nuclear pore is a ______ between
cytoplasm and nucleus

A

gateway

40
Q

how many pores/nucleus

A

3000-4000

41
Q

nuclear pores are found where?

A

where inner and outer
membranes fuses

42
Q

nuclear Contains what… that involve the arrangement of
different types of proteins

A

a complex protein structure

43
Q

The nuclear pore complex (NPC) is composed of

A

nucleoporins (NUPs)—a
large family of different proteins

Octagonal symmetry

Projects into cytoplasm and nucleoplasm

44
Q

The NPC is what type of complex

A

supramolecular

45
Q

the supramolecular complex is very big compared to what

A

a protein arrangement perspective

46
Q

NPC is 15-30 times the size of a what

A

ribosome

47
Q

Passive diffusion of molecules
that are 40 kDA or less is

A

Rapid, 100 molecules/minute/pore

48
Q

Regulated movement of larger molecules is

A
  • Slow
  • 6 molecules/minute/pore
49
Q

NLS = ?

A

several positively charged amino acids within the protein sequence

50
Q

Regulated movement of proteins into the nucleus requires an intrinsic
amino acid targeting sequence called what

A

Nuclear Localization Signal (NLS)

51
Q

How does the NLS targets proteins to the nucleus: Protein with NLS (cargo) interacts with

A

Importin protein in cytoplasm

52
Q

Cargo/Importin complex interacts with what

A

FG-NUPs at the NPC and enters the nucleoplasm

53
Q

Ran-GTP (G-protein) interacts with what

A

Importin; cargo dissociates and stays in nucleoplasm

54
Q

Ran-GTP/Importin complex exits
nucleus through what

A

NPC nuclear pore complex

55
Q

GTP hydrolysed to GDP. Importin is released in what

A

cytoplasm to find new cargo

56
Q

Nuclear import and export are critical for what

A

cellular function

57
Q

cellular function in terms of nuclear import/export includes

A
  • 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
Q

the nucleolus is the largest structure inside what

A

the nucleus of eukaryotic cells and is NOT membrane-bound

59
Q

Primary function of the nucleolus
is what

A

biosynthesis of ribosomes

60
Q

Ribosomes consist of two major components. describe them

A

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
Q

Ribosome Biosynthesis includes (5) things

A
  • 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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