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BMS241 final exam > Topic 11 - Cellular Communities: Tissues, Stem Cells, and Cancer > Flashcards

Topic 11 - Cellular Communities: Tissues, Stem Cells, and Cancer Flashcards

1
Q

extracellular matrix greatly strengthens plant cells and is made of…?

A

cellulose & polysaccharides (lignin & pectin)

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2
Q

turgor pressure is what?

A

osmotic pressure in plant cells (crisp lettuce)

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3
Q

What gives the Plant Cell Wall Its Tensile Strength

A

cellulose microfibrils

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4
Q

T or F - cellulose is the most abundant organic macromolecule on Earth

A

true

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5
Q

T or F - The orientation of cellulose microfibrils within the plant cell wall influences the direction in which the
cell elongates

A

true

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6
Q

What directs the deposition of cellulose in the plant cell wall?

A

microtubules

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7
Q

T or F - cellulose microfibrils are deposited on the exterior, directly parallel to underlying microtubules

A

true

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8
Q

It is traditional to distinguish four major types of tissues in animals: con- nective, epithelial, nervous, and muscular. But the basic architectural distinction is between … tissues and the rest.

A

connective

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9
Q

Animal Connective Tissues Consist Largely of

A

the extracellular matrix

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10
Q

the tensile strength in animal connective tissue comes from …?

A

collagen

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11
Q

Mammals have about ?? different collagen genes, coding for the variant forms of collagen required in different tissues

A

20

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12
Q

Collagens constitute ??% of the total protein mass in a mammal—more than any other type of protein

A

25%

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13
Q

The characteristic feature of a typical collagen molecule is its ?

A

long, stiff, triple-stranded helical structure

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14
Q

The connective-tissue cells that manufacture and inhabit the matrix go by various names according to the tissue: in skin, tendon, and many other connective tissues they are called …?

A

fibroblasts

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15
Q

The connective-tissue cells that manufacture and inhabit the matrix go by various names according to the tissue: in bone, they are called …?

A

osteoblasts

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16
Q

Collagen is synthesised in the cell and exported as a …? Cleaved by what?

A

procollagen - cleaved by extracellular Procollagen proteinases

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17
Q

Collagen analogy…?

A

Collagens are like ropes or the steel bars in a slab of concrete: anti-stretch

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18
Q

Patients with genetic defects in procollagen proteinases?

A

Lower tensile strength and extremely stretchy tissues (man with stretchy face)

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19
Q

?? organise the collagen matrix, and the organisation of the matrix determines the positioning of ??

A

fibroblasts

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20
Q

What links the cells with the extra cellular matrix?

A

fibronectin

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21
Q

Remember structure of fibronectin… (hint: hand analogy)

A

like thumb & index finger attached to wrist - disulphide linked (integrin dimers) hold collagen fibril

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22
Q

T or F - Integrin active state can be triggered by binding to an extracellular matrix molecule (such as fibronectin) or to intracellular proteins that then link it to the cytoskeleton

A

true

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23
Q

leucocyte adhesion deficiency is caused by what?

A

people who lack integrins on white blood cells help those cells to crawl out of blood vessels at sites of infec-
tion so as to deal with the marauding microbes

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24
Q

While collagen provides tensile strength to resist stretching, a completely different group of macromolecules in the extracellular matrix of animal tissues provides the complementary function, resisting compression and serving as space-fillers. These are the…? what structures do they link to?

A

proteoglycans, link to glycosamoniglycans (GAGs)

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25
Q

The negative charge on the GAGs attracts … & …?

A

cations like Na+ -> water -> ++ swelling pressure

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26
Q

GAGs & collagen work together. how? tissue eg’s

A

GAGs: swelling pressure + collagen: tensile strength = tough, resilient, and resistant to compression
eg. cartilage matrix in knee joint

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27
Q

The majority of cell types in the body are organized into…?

A

epithelia (skin, gut…)

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28
Q

What molecules allow ECM to modulate cell behaviour? These are also important in resisting compression.

A

proteoglycans

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29
Q

What are the 5 types of epithelia? eg. of 2 type…

A 
SSSCC
Simple - gut lining 
Stratified - skin
Squamous - 
Columnar - small intestines
cuboidal -
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30
Q

Epithelial cells are … and rest on a …?

A

polarised & basal lamina (cool SEM of chick embryo basal lamina)

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31
Q

A sheet of epithelial cells has an 2 surfaces. One is ‘free’ and the other sits on the basal lamina

A

apical surface and basal surface

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32
Q

Define polarized… eg.

A

spatial differences in the shape, structure, and function of cells. ie. one side has different properties to the other
eg. neuron or epithelial cell

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33
Q

The basal lamina is usually tough, consisting of interwoven … & …?

A

Type IV collagen and Laminin

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34
Q

Know figure 20-22 (MCQ)…

A

easy

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35
Q

The membrane polarisation of epithelial cells is established by …?

A

tight junctions

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36
Q

Cytoskeleton-linked Junctions Bind Epithelial Cells Robustly to One Another and to the Basal Lamina. which 3 are they? Remember figure 20-22 (MCQ figure)

A
  1. adherens junctions
  2. desmosomes
  3. hemidesmosomes
37
Q

Adherens junctions and desmosomes are both built around transmem- brane proteins that belong to the … family?

A

cadherins

38
Q

A cadherin is a transmembrane molecule that undergoes extracellular … reactions with cadherin on an adjacent cell

A

homophilic (binding of like to like)

39
Q

At an adherens junction, cadherins are tethered via adaptors to … filaments

A

actin

40
Q

Formation of the neural tube; the scanning electron micrograph shows a cross section through the trunk of a two-day chick embryo. Part of the epithelial sheet that covers the surface of the embryo has thickened, has rolled up into a tube by …?

A

apical contraction

41
Q

At a desmosome, by contrast, a different set of cadherin molecules are anchored inside each cell. These cadherins connect to … filaments; specifically to …?

A

intermediate filaments - keratins

42
Q

Hemidesmosomes anchor the keratin filaments in an epithelial cell to the basal lamina. The linkage is mediated not by cadherins, but by

A

integrins

43
Q

T or F - Gap junctions in many tissues can be opened or closed as needed in response to extracellular signals.

A

true

44
Q

The neurotransmitter … for example, reduces gap-junction communication within a class of neurons in the retina in response to an increase in light intensity

A

dopamine

45
Q

The counterpart junction in plant cells (the only junction in plants) of gap junctions is called …?

A

plasmodesmata

46
Q

Connexon proteins form ?

A

open channels between adjacent cells ie. gap junctions

47
Q

Moreover, in almost all adult tissues, cells are continually dying and being replacedE;CtBh3ro2u1g.h3o4u/t2th0i.s3h4urly-burly of cell replacement and tissue renewal, the organization of the tissue must be preserved. Three main factors contribute to this stability…

A
  1. cell communication:
  2. selective cell-cell adhesion:
  3. cell memory:
48
Q

How many cells in the human body?

A

20 - 100 trillion

49
Q

Different Tissues Are Renewed at Different Rates. Times for the following: bone, neuron, epidermis, RBCs

A

bone - 10 yrs
neuron - persist forever
epidermis - 2 months
RBCs - 3 months

50
Q

Which differentiated cells that need continual replacement are themselves unable to divide?

A

RBCs, surface epidermal cells & absorptive goblet cells - terminally differentiated

51
Q

Define terminally differentiated…

A

Many of the differentiated cells that need continual replacement are themselves unable to divide ie they lie at the dead end of their developmental pathway

52
Q

The gut epithelium as an example of stem cell renewal of tissues. THIS MAY BE A SAQ IN EXAM - know it well! Remember cells of the gut (SI) epithelium & how dividing stem cells give rise to terminally differentiated epithelial cells…

A

draw…figure 20-36
Paneth cells -> secrete anti-bacterials
Enterendocrine cells -> gut hormones
Goblet cells -> mucous
Brush border cells -> absorb nutrients via microvilli
Stem cells -> dividing precursor cells -> nondividing terminally differentiated cells

53
Q

The Wnt protein does what?

A

serve to keep the stem cells and precursor cells at the base of each intestinal crypt in a proliferative state

54
Q

Define pluripotent…

A

embryonic stem cells (ESCs) from ICM that retain unrestricted developmental potential ie. stem cell that has the potential to differentiate into any of the three germ layers

55
Q

Define multipotent…eg…

A

potential to differentiate into multiple, but limited cell types. For example, a multipotent blood stem cell is a hematopoietic cell (blood stem cell)

56
Q

Define totipotent…

A

the ability of a single cell to divide and produce all of the differentiated cells in an organism eg. zygote cells

57
Q

Define clone…

A

set of individuals that are genetically identical by virtue of their descent from a single ancestor

58
Q

Define therapeutic cloning…

A

…embryo -> culture -> various personalised ES cells -> tissue repair

59
Q

Define reproductive cloning…

A

…embryo -> foster mother -> offspring genetically identical to the nuclear donor

60
Q

Transgenic expression of three genes in human adult fibroblasts will revert them to embryonic stem cell character. what are these cells called? what are the 3 genes?

A

induced pluripotent stem cells (iPS cells)

  • Oct 3/4
  • Sox2
  • Klf4
61
Q

Cancer cells are defined by two heritable properties: they and their progeny:

A
  1. proliferate in defiance of the normal constraints

2. invade and colonize territories normally reserved for other cells

62
Q

If cells break the 1st property: proliferate in defiance of the normal constraints - what is caused?

A

benign tumour

63
Q

A tumor is cancerous only if its cells have the ability to invade surrounding tissue, in which case the tumor is said to be …?

A

malignant

64
Q

Define metastases…

A

Malignant tumor cells with this invasive property can break loose from the primary tumor, enter the bloodstream or lym- phatic vessels, and form secondary tumours

65
Q

Define epidemiology…

A

the statistical analysis of human populations that is used to look for factors that correlate with disease incidence

66
Q

In order to produce metastases, cancer cells must be able to: (5 steps)

A
  1. migrate
  2. Digest the ECM of the basal lamina
  3. Enter the bloodstream
  4. Exit the bloodstream
  5. Colonise and thrive in a new environment
67
Q

T or F - In the great majority of human cancers, however, viruses do not appear to play a part

A

true

68
Q

By far the most important environmental cause of cancer in the modern world, however, is …?

A

tobacco-smoking

69
Q

T or F - Cancer is fundamentally a genetic disease

A

true

70
Q

Cancer differs from other genetic diseases in that the mutations underlying cancer are mainly germ-line or somatic?

A

somatic

71
Q

Define genetic instability…

A

human cancer cells mutations that interfere with the accurate replication and maintenance of the genome and thereby increase the mutation rate itself

72
Q

How many gene mutations in a hunam i their whole life?

A

> 10^9

73
Q

Different cancers require different combinations of properties. Never- theless, we can draw up a general list of key behaviors of cancer cells that distinguish them from normal cells… (could be SAQ in exam)

A
  1. don’t rely on signals from other cells as cues for growth, survival & proliferation - often as mutation is in cell signalling pathway eg. Ras gene mutation -> proliferation even in absence extracellular signal
  2. less prone to apoptosis cos mutations in genes that regulate cell death eg. about 50% of all human cancers have lost or suffered a mutation in the p53 gene
  3. can proliferate indefinitely by reactivating production of the telomerase enzyme
  4. genetically unstable, with a greatly increased mutation rate
  5. abnormally invasive due to lack specific cell-adhesion molecules, such as cadherins
  6. survive and proliferate in foreign tissues (metastases) whereas most normal cells die when misplaced
74
Q

What is the role of VEGF?

A

vascular endothelial growth factor - stimulate the neovascularisation of tumours (and normal tissue for wound repair) -> supply a highway for metastases to colonise the rest of the body

75
Q

normal cellular gene that can be converted to an oncogene?

A

proto-oncogene

76
Q

What are the 4 mechanisms of proto-oncogene -> oncogene…?

A
  1. mutation in coding sequence - hyperactive protein in normal amounts
  2. gene amplification - normal protein greatly produced
  3. chromosome rearrangement 1 - regulatory DNA sequences -> normal protein overproduced
  4. chromosome rearrangement 2 - fusion to actively transcribed gene -> hyperactive fusion protein
77
Q

Get your head around 20-49 (big mother fucker)

A

may be SAQ in exam

78
Q

The role of the Adenomatosis Polyposis Coli (APC) protein in the development of colorectal carcinoma happens how?

A

APC keeps Wnt gene in check
thus…
loss of APC -> Wnt pathway hyperactive (crypts in gut lining) -> proliferate to excess, generating a polyp -> further mutations may occur, resulting in invasive cancer

79
Q

What % of colorectal cancers have lost APC function?

A

60%

80
Q

How we know: What approach that was taken to characterize APC?

A

co-immunoprecipitation (Ab)

81
Q

What does APC bind to?

A

beta-catenin

82
Q

Diagnosis of a tumour at the 1cm stage = ? cells

A

10^9

83
Q

first line of therapy?

A

sx

84
Q

Cancer cells that lack DNA damage control can be targeted by ?

A

chemotherapy or radiotherapy

85
Q

Drugs against VEGF aimed to prevent ?

A

angiogenesis

86
Q

why might several anti-VEGF drugs are not as helpful as was hoped?

A

some tumour blood vessels originate in cancers

87
Q

Chronic myeloid leukaemia is caused by a specific translocation that affects a particular tyrosine kinase by removing its negative regulatory domain (Fig. 20-48) to propagate a mitogenic signal. A specific inhibitor for that kinase that kills cancer cells and gives remission of symptoms is called what?

A

gleevec

88
Q

How does gleevec prevent leukaemia?

A

binds to oncogenic kinase (where ATP usually binds & activates it) -> inactive kinase -> no signal

BMS241 final exam (5 decks)

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