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Molecular Cell Bio > chapter 20 > Flashcards

chapter 20 Flashcards

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Biology 101 flashcards
1
Q

intestine is constructed from _, _, and _. Each tissue is an organized assembly of _, held together by _, _, or both.

A

epithelial tissues
_
connective tissues
_
muscle tissues
_
cells
-
cell-cell adhesions
_
extracellular matrix

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1
Q

Collagen fibrils are organized into _

A

bundles.

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2
Q

collagen assembly steps:

A

from individual polypeptide chains to triple-stranded collagen molecules, then to fibrils and, finally, fibers.

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3
Q

fibroblast secretes:

A

secretes collagen and other extracellular matrix components.

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4
Q

Collagen is the main protein in

A

animal connective tissues, like bone, skin, and tendons.

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5
Q

_ is the main protein in animal connective tissues, like bone, skin, and tendons.

A

Collagen

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6
Q

_ can cause the skin to be hyperextensible.
In some individuals, this condition arises from a lack of _; in others, it is caused by a defect in _.

A

Incorrect collagen assembly
_
an enzyme that converts procollagen to collagen
_
procollagen itself

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7
Q

Incorrect collagen assembly can cause _

A

the skin to be hyperextensible.

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8
Q

Fibronectin and transmembrane integrin proteins help _

A

attach a cell to the extracellular matrix.

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9
Q

_ help attach a cell to the extracellular matrix.

A

Fibronectin and transmembrane integrin proteins

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10
Q

Fibronectin molecules bind to _.

A

collagen fibrils outside the cell

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11
Q

Integrins in the plasma membrane bind to _

A

the fibronectin and tie it to the cytoskeleton inside the cell.

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12
Q

(fig.14) The integrin molecule transmits _ across the _: it is anchored inside the cell via _ to the actin cytoskeleton and externally via _ to other extracellular matrix proteins

A

tension
_
plasma membrane
_
adaptor proteins
_
fibronectin

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13
Q

An integrin protein _ when it binds to molecules on either side of the plasma membrane.

A

switches to an active conformation

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14
Q

An integrin protein consists
of two different subunits, _, both of which can switch between a _, _ form and an _, _ form. The switch to the activated state can be triggered by _ or _ that then _ (see Figure 20–14). In both cases, the conformational change alters the integrin so that _.
In this way, the integrin establishes a _ mechanical linkage across the plasma membrane.

A

α and β
_
folded
_
inactive
_
extended
_
active
_
binding to an extracellular matrix molecule (such as fibronectin)
_
to intracellular adaptor proteins
_
link the integrin to the cytoskeleton
_
its opposite end rapidly forms a counterbalancing attachment to the appropriate structure
_
reversible

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15
Q

In the extracellular matrix (ECM), different components handle different tasks:

Collagen provides _.
Glycosaminoglycans (GAGs) and proteoglycans _.

A

strength to resist stretching
_
help resist compression

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16
Q

In the extracellular matrix (ECM), different components handle different tasks:

_ provides strength to resist stretching.
_ help resist compression.

A

Collagen
_
Glycosaminoglycans (GAGs) and proteoglycans

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17
Q

(fig. 17) Proteoglycans and GAGs can form large aggregates.
it is built up from _ subunits bristling with numerous _—chondroitin sulfate (long blue lines) and keratan sulfate (short blue lines)—attached to a _ (light green). These subunits then aggregate via _ (green) to the _

A

aggrecan
GAG chains
core protein
link proteins
GAG hyaluronan

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18
Q

The basal surface sits on
a _ called the basal lamina

A

specialized sheet of extracellular matrix

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19
Q

Tight junctions allow epithelial cell sheets to serve as _.

A

barriers to solute diffusion

20
Q

cells are sealed together by branching strands (C) of transmembrane proteins (green), called _

A

claudins and occludins

21
Q

Cadherin proteins mediate
_ attachment of one cell to
another.

A

mechanical

22
Q

Identical cadherin molecules in the
plasma membranes of adjacent cells bind
to each other extracellularly; inside the cell,
they are attached, via _, to
_—either _ or _.

A

linker proteins
cytoskeletal filaments
actin filaments
keratin intermediate filaments

23
Q

when epithelial
cells in culture touch one another, their
cadherins become concentrated at the point of attachment, leading to _

A

the formation of adherens junctions.

24
Q

Adherens junctions form _ around epithelial cells in the small intestine.

A

adhesion belts

25
Q

A contractile bundle of actin filaments runs along the cytoplasmic surface of the plasma membrane near the apex of each cell. These bundles are linked to those in adjacent cells via transmembrane _ molecules

A

cadherin

26
Q

A bundle of keratin filaments is attached to _.
The cytoplasmic tails of transmembrane cadherin proteins bind to the _; their extracellular domains interact
to hold the cells together.

A

the surface of each plaque, composed of a mixture of intracellular linker proteins.
_
outer face of each plaque
_

27
Q

Gap junctions provide neighboring cells with a _ mediated by _

A

direct channel of intercytosolic communication
_
protein assemblies called connexons

28
Q

connexons: formed from _. Two connexons join across the intercellular gap to form _ connecting the cytosols of the two cells.

A

six identical protein subunits
an aqueous channel

29
Q

tight junctions are peculiar to _

A

epithelia

30
Q

name all the junctions:

A

tight junction

adherens junction

desmosome

gap junction

hemidesmosome

31
Q

hemidesmosome:

A

anchors intermediate filaments in a cell to the basal lamina

32
Q

Skin can be viewed as a large organ composed
of two main tissues: _ on the outside, and _ on the inside.

A

epithelial tissue (the epidermis)
connective tissue

33
Q

The underlying connective tissue consists of the tough dermis (from which leather is made) and the deeper, _.

A

fatty hypodermis

34
Q

The dermis and hypodermis are richly supplied with _; some of the _ extend into the epidermis.

A

blood vessels and nerves
nerves

35
Q

_ connective tissue of HYPODERMIS

A

fatty

36
Q

_ connective tissue of DERMIS

A

dense

37
Q

_ connective tissue of DERMIS

A

loose

38
Q

When a stem cell divides, each daughter can either _ or _

A

remain a stem cell (self-renewal)
_
go on to become terminally differentiated.

39
Q

The terminally differentiated cells usually develop from _ that divide a _.

A

proliferating precursor cells
_
limited number of times before they terminally differentiate

40
Q

in the intestines, The stem cells give rise mainly to _, which slide continuously _ and terminally differentiate into _ (purple) or _ (blue) cells, which are shed from the _. The stem cells also give rise _, which move down to the bottom of the crypt.

A

proliferating precursor cells
_
upward
_
secretory
_
absorptive
_
tip of the villus
_
directly to terminally differentiated Paneth cells
_

41
Q

Mouse ES cells can be induced to differentiate into specific cell types in culture:

A

fat cell
neuron
macrophage
heart muscle cell
glial cells

42
Q

Tumors evolve by _

A

repeated rounds of mutation, proliferation, and natural selection.

43
Q

A small number of key regulatory pathways are perturbed in almost all human cancers:

A

ALTERATIONS IN CELL PROLIFERATION
ALTERATIONS IN DNA DAMAGE RESPONSE
ALTERATIONS IN CELL GROWTH
ALTERATIONS IN CELL SURVIVAL

44
Q

how can we progress to Colorectal cancer

A

INACTIVATION OF BOTH COPIES OF TUMOR SUPPRESSOR GENE (APC )
_
= excessive proliferation of the mutant cells (=polyp)
_
ONE COPY OF PROTO- ONCOGENE (Ras) ACTIVATED
_
= small tumor
_
SEQUENTIAL INACTIVATION OF BOTH COPIES OF ANOTHER TUMOR SUPPRESSOR GENE
_
= large tumor
_
SEQUENTIAL INACTIVATION OF BOTH COPIES OF A THIRD TUMOR SUPPRESSOR GENE (p53)
_
tumor becomes invasive cancer
_
RAPID ACCUMULATION OF OTHER DRIVER MUTATIONS
_
= metastasis

45
Q

Wnt proteins: _

A

These signals are crucial for promoting the division of stem cells and precursor cells at the base of intestinal crypts.

46
Q

The _ keeps the Wnt signaling pathway inactive when the cell is not exposed to a _. It does this by promoting degradation of the _.

A

APC protein
secreted Wnt signal protein.
signaling molecule β-catenin

47
Q

In the presence of Wnt (or in the absence of active APC), free β-catenin becomes plentiful and combines with the _ to drive _ and, ultimately, the proliferation
of stem cells and precursor cells in the intestinal crypt

A

transcription regulator TCF
transcription of Wnt-responsive genes

48
Q

In the colon, mutations that inactivate _ initiate tumors by causing excessive activation of the _.

A

APC
Wnt signaling pathway

Molecular Cell Bio (13 decks)

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