Cell Bio Lecture 21

Front 1

ramping

Back 1

increase stimulation of the inspiratory muscles for 2 seconds

Front 2

blah

Back 2

blah

Front 3

Cytoskeleton
-composition

Back 3

made up of 3 filaments
(actin, microtubules, and intermediate filaments)
strong but flexible, accessory proteins hold together

Front 4

Cytoplasm
-functions

Back 4

allows movement and responds to changes in the environment
1) permitting direct movement (interior movement)
2) support: IF is critical for support of shear mechanical stresses

Front 5

Cytoplasm
-functions in nature

Back 5

1) cell locomotion and movement (would healing, tissue repair, development)
2) cell division (cytokinesis is cell separation)

Front 6

Cytoplasm (continued)
-functions in nature

Back 6

3) Intracellular Motility (vesicular traffic on MT and A
-endo and exocytosis
-no IF here because no known mmotors for IF)
4)early development (fertilization and tissue morphogenesis

Front 7

Microtubules

Back 7

hollow cylinders (tubulin)
primary organizers (positions of organelles)
direct intracellular transport

Front 8

Microfilaments/Actin

Back 8

2 stranded helical polymers
shape of cell surface
necessary for whole cell locomotion

Front 9

Intermediate Filaments

Back 9

ropelike (numerous subunits)
mechnical strength of cell
resistance to shear stress
in particular for metazoans, but not all of them have them

Front 10

The 3 filaments are located always in?
subunits

Back 10

cytoplasmic pools and polymerized pools at all times

Front 11

Cytoskeletal filament are constructed from

Back 11

smaller protein subunits

Front 12

Cytoskeletal filament are ___ and have ____

Back 12

dynamic; able to change to suit the needs of the cell
1) helical assemblies
2) self-associate
3) differences in subunit shape and the attractive forces between them

Front 13

Cytoskeleton: dynamic properties

Back 13

constantly undergoing assembly-disassembly reactions
-perform diverse variety of functions

Front 14

Accessory Proteins regulate___

Back 14

the spatial distribution and dynamic behavior of filaments
-determine site of assembly
-regulate partitioning
-harness energy to make filaments
-link filaments
-change kinetics of assembly/disassembly

Front 15

Accessory Proteins can do what to the reaction?

Back 15

speed up or slow down or prevent the reaction all together

Front 16

Advantages: Multiple Protofilaments

Back 16

multiple protofilaments are thermally stable
-to break need to break symmetry and 3 bonds
-noncovalent interactions

Front 17

Is a single strand of a filament functional?

Back 17

No

Front 18

Which of the filaments have chemically distinct ends

Back 18

A and MT

Front 19

MT and A have these qualities in common...

Back 19

bind nucleotides, made up of small globular subunits, polar, and have motors

Front 20

Nucleation: rate limiting step in formation of skeletal polymer

Back 20

consists of the lag phase, growth phase, equilibrium phase

Front 21

Lag phase

Back 21

a part of nucleation: corresponds to time taken for nucleation, need to be in one place long enough to form a seed

Front 22

growth phase

Back 22

occurs as monomers add to the exposed ends of the growing filament, causing filament elongation

Front 23

Equilibrium phase

Back 23

reached when the growth of the polymer due to monomer addition is precisely balanced by the shrinkage of the polymer due to dissembly back to monomers

Front 24

net loss

Back 24

fall off faster than they aggregate

Front 25

nucleus consists of what

Back 25

helical polymer that is stabilized by multiple contacts btw adjacent subunits

Front 26

Critical concentration

Back 26

K off / k on

Front 27

IF network

Back 27

principle structural element
-form extensive networks
-function to resist mechanical stress
-provide anchorage
-not required in every cell type
-closely associate with microtubules in cells
-both cytoplasmic and nuclear IF

Front 28

Every eukaryotic cell has ____

Back 28

nuclear IF but not necessarily cytoplasmic IF

Front 29

Large families of IF proteins

Back 29

subunits vary in size
-much more diverse, often compact (MT/A are much more uniform)
-classified by their ability to copolymerize

Front 30

Type of IF proteins

Back 30

epithelial: Type I (acidic)
-type II (basic)

vimentin-like
axonal: neurofilament proteins which are involved in teathering the chromosomes to nuclear pores
-nuclear: lamins A,B,C

Front 31

IF protein subunit structure

Back 31

3 domains:
N-terminal globular (head domain)
Central rod-like domain
C-terminal globular

Front 32

N-terminal globular

Back 32

head domain
varies

Front 33

Central rod-like domain

Back 33

alpha helical
responsible for self-assembly of monomers to dimers
40 of so heptad repeats

Front 34

C-terminal globular

Back 34

tail domain
varies

Front 35

the smallest structural subunit

Back 35

antiparallel dimer: 4 proteins for IF not the DIMER

Front 36

IF assemble into

Back 36

higher order structures
-2 dimers in antiparallel forms non-polar tetrameric units (smallest soluble subunit of IF)

Front 37

Tetramers bind along the

Back 37

long axis forming protofilaments that pack together in an intertwined helical pattern within polymer
-8 tetramers: 32 individual alpha-helical coils

Front 38

IF lacks polarity

Back 38

because the ends are the same

Front 39

Strong lateral contacts

Back 39

rope-like properties
-noncovalently associated
-important to build these stacked structures because they are tougher to break apart

Front 40

Epithelial

Back 40

most diverse family of IF
-composed of a large number of different subunits
-acidic keratins (type 1)
-basic keratins (type II)
-"hard" cytokeratins

Front 41

Heterodimers can form...

Back 41

IFs but homodimers cant.
thus all keratin filaments contain equimolar ratios of acidic and basic subunits

Front 42

Vimentin-like family of IF

Back 42

cells from mesenchymal origin
-desmin (muscle, skeletal, cardiac)
-glial fibrillary acidic protein (GFAP)
-peripherin (some neurons)
-can self-assemble into homopolymers and/or copolymerize with each other

Front 43

Axonal family of IF

Back 43

found in neurons (especially rich in axons where they are highly bundled)
-NF low 70 kd
-NF mid 150 kd
-NF high 210 kd

Front 44

The extra long carboxy-terminal tail of mid and high are thought to

Back 44

form crossbridges between the bundles of IF's in the axon

Front 45

Nuclear family of IF

Back 45

Lamins A,B,C 65-75 kd
-central rod domain is longer than other IF subuits
-contain nuclear localization sequence
-assemble into 2-d sheets on the inner nuclear membrane
-present in all eukaryotic cells

Front 46

Nuclear family of IF
function

Back 46

form nuclear lamina- meshwork stabilizing the nuclear envelope and helping to organize the chromatin

Front 47

Phosphorylation

Back 47

will cause it to dissemble

Front 48

Summary of IF properties

Back 48

heterogeneous
form strong flexible rope-like structures
-serve as the "ligaments" of the cell