Test 3. Lecture 29

Question 1

__________ are MICROTUBULE BASED PROJECTIONS of the plasma
membrane, responsible for
movement of a variety of eukaryotic
cells.

Answer 1

cilia and flagella

Question 2

Some bacteria have______, but they
are protein filaments projecting
from the cell surface.

Answer 2

flagella`

Question 3

_________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.

Answer 3

Cilia

flagella`

Question 4

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.

Answer 4

axonemeaxoneme

Nexin
dynein

Question 5

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.

Answer 5

basal body

9 triplets of microtubles

Question 6

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.

Answer 6

axonemal dyneins

Question 7

Microtubules completely reorganize

during ___________

Answer 7

mitosis

Question 8

Interphase microtubule array
disassembles and free tubulin
subunits are reassembled into
the ____________

Answer 8

mitotic spindle.

Question 9

The centrosome is duplicated in

_________

Answer 9

interphase.

Question 10

During __________, the centrosomes
migrate to form the two poles of
the mitotic spindle.

Answer 10

prophase

Question 11

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.

Answer 11

mitosis

Question 12

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.

Answer 12

1. Kinetochore microtubules
2. Chromosomal microtubules

3 Polar microtubules

4 Astral

________________________

1. Kinetochore microtubules attach to the condensed chromosomes at
   the centromeres, stabilizing them.
2. Chromosomal microtubules connect to chromosome ends via
   chromokinesin.
3. Polar microtubules are not attached to chromosomes but are stabilized
   by overlapping with each other in the center of the cell.
4. 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.

Question 13

Chromosome movement occurs by what two movements?

Answer 13

1. Anaphase A

2. Anaphase B

Question 14

describe Anaphase A-

Answer 14

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

Question 15

describe Anaphase B-

Answer 15

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.

Question 16

________________: diameters intermediate between actin

filaments and microtubules.

Answer 16

Intermediate filaments

Question 17

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.

Answer 17

mechanical

strength

Question 18

Type I and II are ________, in epithelial cells.
___________ forms a network extending out from the nucleus toward
the cell periphery

Answer 18

keratins

Vimentin

Question 19

_____________ are the major intermediate filaments of many neurons;
provide support for long axons.

Answer 19

Neurofilament (NF) proteins (with α-internexin)

Question 20

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.

Answer 20

Nestins

Type V

head and tail

Question 21

_____________: 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 ____________

Answer 21

Filament assembly

filament.

Question 22

Name two speicalized cell contacts -

Answer 22

desmosomes and keratin filaments

Question 23

Desmosomes define?

Answer 23

junctions BETWEEN ADJACENT CELLS

Question 24

In Desomosomes- __________ attach to dense protein plaques on the cytoplasmic side

Answer 24

keratin filaments

Question 25

define hemidesmosomes-

Answer 25

junctions between EPITHELIAL CELLS AND UNDERLYING CONNECTIVE TISSUE

Question 26

in hemidesmosomes, _____________ are attached to different plakins (plectin) transmembrane integrins link to the extracellular matrix

Answer 26

keratin filaments

Question 27

Direct evidence for the function of intermediate filaments is recent.

1. Some cells in culture don’t make intermediate filaments.
2. 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.
   .
3. 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.

Answer 27

general information

Question 28

1. Many cells are surrounded by insoluble secreted
   macromolecules.
   Cells of bacteria, fungi, algae, and higher plants are surrounded
   by rigid cell walls.
2. 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.

Answer 28

General information

Question 29

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.

Answer 29

Basal laminae

Question 30

1. Extracellular matrix is most abundant in _____________
   Connective tissues (loose connective tissue, bone, tendon, and
   cartilage) consist mostly of extracellular matrix with cells
   distributed throughout.
2. Extracellular matrices have tough ___________ embedded in a
   gel-like polysaccharide.
3. ____________ link components of the matrix to one another
   and to cells.
4. 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.

Answer 30

connective tissues

fibrous proteins.

Adhesion proteins

Tendons
Cartilage
Bone matrix

Question 31

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).

Answer 31

glycine

Question 32

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.

Answer 32

Proline hydroxyproline

Hydroxyl groups