Test 3. Lecture 29 Flashcards
__________ are MICROTUBULE BASED PROJECTIONS of the plasma
membrane, responsible for
movement of a variety of eukaryotic
cells.
cilia and flagella
Some bacteria have______, but they
are protein filaments projecting
from the cell surface.
flagella`
_________beat in a coordinated back-andforth
motion, which either moves
the cell through fluid or moves fluid
over the surface of the cell.
__________ are longer, and have a
wavelike pattern of beating.
Cilia
flagella`
Structure of cilia and flagella is similar:
The ________ consists of microtubules in a “9 + 2” pattern: a central pair
surrounded by 9 outer doublets.
Each doublet is a complete A tubule fused to an incomplete B tubule.
______links the tubules, and 2 arms of __________ are attached to each A
tubule.
axonemeaxoneme
Nexin
dynein
The microtubule minus ends are anchored in a __________, similar in
structure to a centriole.
It has _________ of microtubules.
Basal bodies initiate growth of axonemal microtubules and anchor cilia and
flagella to the surface of the cell.
basal body
9 triplets of microtubles
Movement of cilia and flagella results from sliding of outer microtubule
doublets relative to one another, powered by motor activity of
__________________.
Dynein BASES BIND TO A TUBULES, while the HEAD GROUPS BIND TO B TUBULES
of adjacent doublets.
axonemal dyneins
Microtubules completely reorganize
during ___________
mitosis
Interphase microtubule array
disassembles and free tubulin
subunits are reassembled into
the ____________
mitotic spindle.
The centrosome is duplicated in
_________
interphase.
During __________, the centrosomes
migrate to form the two poles of
the mitotic spindle.
prophase
As the cell enters \_\_\_\_\_\_\_\_\_\_\_, the rate of microtubule disassembly increases, resulting in shrinkage of microtubules. But the number of microtubules emanating from the two centrosomes increases.
mitosis
What four types of microtubules make up the mitotic spindle?:
1. _____________ attach to the condensed chromosomes at
the centromeres, stabilizing them.
2. ____________ connect to chromosome ends via
chromokinesin.
3._____________ are not attached to chromosomes but are stabilized
by overlapping with each other in the center of the cell.
4. __________- extend outward from the centrosomes with the
plus ends anchored in the cell cortex.
- Kinetochore microtubules
- Chromosomal microtubules
3 Polar microtubules
4 Astral
________________________
- Kinetochore microtubules attach to the condensed chromosomes at
the centromeres, stabilizing them. - Chromosomal microtubules connect to chromosome ends via
chromokinesin. - Polar microtubules are not attached to chromosomes but are stabilized
by overlapping with each other in the center of the cell. - Astral microtubules extend outward from the centrosomes with the
plus ends anchored in the cell cortex.
After the centrosomes move to opposite sides of the cell, the duplicated
chromosomes attach to kinetochore and chromosomal microtubules,
and align on the metaphase plate.
Then the links between the sister chromatids are severed and anaphase
begins.
Chromosome movement occurs by what two movements?
- Anaphase A
2. Anaphase B
describe Anaphase A-
chromosomes move toward spindle poles along kinetochore microtubules, driven by kinesins that depolymerize and shorten the tubules.
This is coupled to disassembly and shortening of KINETOCHORE AND CHROMOSOMAL MICROTUBULES, mediated by KINESIN that act as microtubule-depolymerizing enzymes
describe Anaphase B-
spindle poles separate,
accompanied by elongation of polar
microtubules.
The overlapping polar microtubules slide
against one another to push the
spindle poles apart.
Plus-end-directed KINESINS cross-link
polar microtubules and move them
toward the plus end.
Spindle poles are pulled apart by the
astral microtubules.
Cytoplasmic DYNEIN anchored to the cell
cortex moves along astral
microtubules in the minus-end
direction.
Simultaneous depolymerization of astral
microtubules by middle motor
kinesins leads to separation of the
spindle poles.
________________: diameters intermediate between actin
filaments and microtubules.
Intermediate filaments
Intermediate filaments: diameters intermediate between actin
filaments and microtubules.
Not directly involved in cell movements, but provide ___________ and a SCAFFOLD FOR LOCALIZATION of cell processes.
Not found in yeast, plants and some insects.
Intermediate filaments are composed of many types of proteins
that are expressed in different types of cells.
mechanical
strength
Type I and II are ________, in epithelial cells.
___________ forms a network extending out from the nucleus toward
the cell periphery
keratins
Vimentin
_____________ are the major intermediate filaments of many neurons;
provide support for long axons.
Neurofilament (NF) proteins (with α-internexin)
Neurofilament (NF) proteins (with α-internexin) are the major intermediate filaments of many neurons;
provide support for long axons.
____________are expressed during embryonic development in some stem cells.
_________ are the nuclear lamins, which form a meshwork underlying the
nuclear membrane.
Intermediate filaments have a central α-helical rod domain which plays a
central role in filament assembly.
The___________domains determine the specific functions.
Nestins
Type V
head and tail
_____________: the central rod domains of 2 polypeptides form a coiled
coil.
The dimers associate in a staggered antiparallel fashion to form tetramers,
which assemble end-to-end to form protofilaments.
Eight protofilaments wind together to form a ____________
Filament assembly
filament.
Name two speicalized cell contacts -
desmosomes and keratin filaments
Desmosomes define?
junctions BETWEEN ADJACENT CELLS
In Desomosomes- __________ attach to dense protein plaques on the cytoplasmic side
keratin filaments
define hemidesmosomes-
junctions between EPITHELIAL CELLS AND UNDERLYING CONNECTIVE TISSUE
in hemidesmosomes, _____________ are attached to different plakins (plectin) transmembrane integrins link to the extracellular matrix
keratin filaments
Direct evidence for the function of intermediate filaments is recent.
- Some cells in culture don’t make intermediate filaments.
- Injection of cultured cells with ANTIBODY AGAINST VITMENTIN DISTRUPTS INTERMEDIATE FILAMENT networks WITHOUT AFFECTING CELL GROWTH OR MOVEMENT
The primary role of intermediate filaments is probably to strengthen the
cytoskeleton of cells in the tissues of multicellular organisms.
In tissues, cells are subjected to a variety of mechanical stresses that
don’t affect cells in a culture dish.
. - Their role was shown in studies using transgenic mice with a keratin
mutation.
The mutation disrupted formation of a normal keratin cytoskeleton,
resulting in severe skin abnormalities.
general information
- Many cells are surrounded by insoluble secreted
macromolecules.
Cells of bacteria, fungi, algae, and higher plants are surrounded
by rigid cell walls. - Most animal cells are embedded in an extracellular matrix of
proteins and polysaccharides.
The extracellular matrix provides structural support to cells
and tissues and plays important roles in regulating cell
behavior.
Interactions between cells are key to the organization and
communication of cells in the tissues of plants and animals.
General information
Most animal cells are embedded in
an extracellular matrix.
__________: thin layers on which
epithelial cells rest. Also
surrounds muscle cells, adipose
cells, and peripheral nerves.
Basal laminae
- Extracellular matrix is most abundant in _____________
Connective tissues (loose connective tissue, bone, tendon, and
cartilage) consist mostly of extracellular matrix with cells
distributed throughout. - Extracellular matrices have tough ___________ embedded in a
gel-like polysaccharide. - ____________ link components of the matrix to one another
and to cells. - Different types of matrices have different amounts of each
component:
• __________-—high proportion of fibrous proteins.
• __________—high level of polysaccharides that form a
compression-resistant gel.
• ___________is hardened by calcium phosphate crystals.
connective tissues
fibrous proteins.
Adhesion proteins
Tendons
Cartilage
Bone matrix
The major structural protein is collagen.
Collagens form triple helices: three poly-peptide chains are wound together.
Triple helix domains consist of repeats of the amino acid sequence Gly-X-Y (a
________in every 3rd position).
glycine
Glycine is the smallest amino acid. It allows polypeptides to pack closely together.
_______s frequently found in the X position and ____________ in the Y position.
They stabilize the helices.
Hydroxyproline is formed in the ER by modification of proline in collagen polypeptide
chains.
___________-are thought to stabilize the triple helix by forming hydrogen bonds.
Proline hydroxyproline
Hydroxyl groups
