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Term 1 > (bio) unit 8 - Tissues and Cell Communities > Flashcards

(bio) unit 8 - Tissues and Cell Communities Flashcards

1
Q

What is Cytoskeleton

A

a network of fibres forming ‘scaffolding’ within cytoplasm

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2
Q

Why is cytoskeleton important

A
  • determines cell shape, position of organelles
  • allows movement of organelles/components within cells (ex. movement of chromosomes during mitosis)
  • allows movement of cells (‘motility’)
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3
Q

Do prokaryotes have cytoskeletons?

A

yes, they play similar roles in eukaryotes too (cell shape, division, polarity etc,)

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4
Q

What are the three types of cytoskeletal filaments

A
  1. microtubules
  2. intermediate filaments
  3. microfilaments
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5
Q

Intermediate filaments characteristics

(Primary purpose, where can be found, related structures)

A
  • structural / provide mechanical strength (not dynamic)
  • forms a network through cytoplasm of most animal cells, extending out to cell periphery
  • anchored on plasma membrane at cell-cell junctions -> desmosomes
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6
Q

what do Intermediate filaments consist of/ structure

A

long, twisted strands of proteins, each with globular N-terminal head, globular C-terminal and alpha helical rod domain

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7
Q

describe the central rod domains and gllbular ends of intermediate filaments

A
  • central rod domains are all similar in size and AA sequence, so form ropes of similar diameter
  • globular ends are quite variable, interacting with different components within cell
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8
Q

Do all intermediate filaments consist of the same protein?

A

no, intermediate filaments in different cells even within the same organism can be composed of different proteins

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9
Q

What are the two major classes and subclasses of intermediate filaments

A
  1. Cytoplasmic
    - keratins
    - vimenten and vimentin-related
    - neurofilaments
  2. Nuclear
    - nuclear lamins
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10
Q

Where are each class of intermediate filaments found?

A
  • keratins (in epithelia)
  • vimentin and vimentin-related (in connective tissue, muscle cells, neuroglial cells)
  • neurofilaments (in nerve cells)
  • nuclear lamins (in all animal cells)
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11
Q

Characteristic of keratins

A
  • the most diverse class of intermediate filaments
  • every type of epithelium in the body has its own mixture of keratin protein
  • can be used to classify tumours with respect to original cell type
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12
Q

How is keratin exist on skin

A

it is near the surface of the skin to protect you from osmotic shock.

Dead flattened cells packed with keratin

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13
Q

How do intermediate filaments support the nuclear envelope and what is it involved in

A
  • nuclear lamins form 2D mesh rather than ropes that lay along the nuclear envelope
  • involved in processes such as DNA replication and mitosis , breaks down and reforms as cell mitoses
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14
Q

Characteristics of microtubules

A
  • largest diameter; hollow, relatively stiff
  • organizes roles in all eukaryotic cells
  • creates a system of tracks for movement of vesicles/organelles
  • anchor organelles in place
  • form mitotic spindle
  • forms stable structures on certain cells - cilia, flagella
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15
Q

Describe microtubule organizing centres and give an example

A
  • structures from which microtubules originate and radiate outward
  • in animal cells -> centrosomes
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16
Q

Describe the structure of microtubules

A
  • they are hollow tubes of tubulin
  • these tubulin consist of alpha beta heterodimers that polymerize to form protofilaments
  • protofilaments buildup to form walls of the hollow tube
  • entire tube has polarity due to exposing the alpha portion of the heterodimer on one side and the beta portion on the other side
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17
Q

Are microtubules changing? or stay constant? how

A

they are changing/dynamic
- they are growing and shrinking as subunits are added or removed
- dimers will add spontaneously to the ‘plus’ end

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18
Q

‘plus’ and ‘minus’ end of protofilament/microtubule

A
  • beta end of a protofilament, referred to as the ‘plus end’ of the microtubule
  • this end is where dimers will be added to
  • alpha end of a protofilament, referred to as the ‘minus end’ of the microtubule
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19
Q

How can microtubules extend in length?

A

extended by motor proteins on microtubule tract

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20
Q

What are motor proteins?

A

biological ‘motors’ that are able to move along a suitable surface powered by the hydrolysis of ATP (convert chemical energy into mechanical work)

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21
Q

What are the two types of microtubule motors and what do they do

A
  1. kinesins
    - move towards the ‘plus’ end
  2. dyneins
    - move toward the ‘minus’ end
    - includes motor proteins that drive movement of cili and flagella
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22
Q

How are cilia and flagella formed? Where are the bases of these structures formed?

A

microtubules extend to reach the capping proteins along the surface of the cell, the microtubules become stable and thus pushes the cell out.

the base of cilia/flagella occurs at the basal body

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23
Q

Describe Eukaryotic Flagella

A

Eukaryotic flagella:
- made of tubulin
- move by undulating (swimming) motions
- surrounded by plasma membrane

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24
Q

Describe Bacterial Flagella

A

Bacterial flagella:
- made of flagellin
- move the cell by rotating (‘rotary engine’)
- not surrounded by membrane

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25
Q

Describe microfilaments (actin filaments)

(structure and where it exists)

A
  • smallest diameter , ‘threads’
  • polymer of actin subunits called G-actin, create coil of two long strands called F-actin
  • ends are + and -, each end of molecules grows (at + end) and shrinks
  • exists throughout the entire cytoplasm
  • concentrated under plasma membrane
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26
Q

micro filaments (actin filaments) function?

A
  • cell shape/support
  • cell movement
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27
Q

What is the motor protein of microfilament (actin) ? What is it used for

A

myosin
- muscle contraction, vesicle and organelle transport, cell motility, cytokinesis

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28
Q

What is the most important cytoskeletal component for motility of eukaryotic cells without flagella is…
(Describe the steps)

A
  1. actin filaments pushes cell out to make protrusions at ‘leading edge’
  2. protrusions stick to surface (integral membrane proteins assist in this)
  3. rest of the cell drags itself forward
    - involves interaction with myosin - motor protein

slide 46

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29
Q

What lies just outside the plasma membrane in animal cells and bacteria cells

A

animal cells - extracellular matrix (ECM)

bacteria, algae, fungi, plants - cell wall

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30
Q

What are common features of extracellular matrix and cell wall

A
  • strength of support of the cell is provided by cross-linked network of filaments (STEEL RODS)
  • semi solid gelatinous matrix to resist compression (CONCRETE)
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31
Q

What makes plant cells different from animal cells

A
  • plant cells have rigid cell walls
  • they are sedentary, tissues are fairly rigid, weak/fragile if separated from their cell walls bc they have no intermediate filaments unlike animal cells
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32
Q

primary cell wall of plant cell and what is it made up of

A
  • secreted as cells are growing, relatively thin
  • consist of pectins (made in rough ER/golgi, picks up water for gelatinous)
  • consists of cellulose (made in plasma membrane)
33
Q

When are secondary cell wall formed in plant cells

A

formed once growth of the primary cell wall of the plant cell has stopped

34
Q

Secondary Cell wall in plant cells

(where are they found and how does it help the cell)

A
  • enclosed by the primary cell wall
    -thicker than primary wall allows cell to become rigid
  • found only in certain cell types as they mature
35
Q

describe some ways the secondary cell wall in plant cells can be useful for (3)

A

depends on plant+cell type
- STRUCTURE (high cellulose content)
- WATERPROOF (waxes)
- PROTECTION against pathogens / drought (lignins)

36
Q

How are plant cells encased in a wall able to grow?

A
  • driving force for growth of a plant cell is a turgor pressure
  • orientation of cellulose microfibrils determines the direction of growth of a plant cell
37
Q

What provides the template for cellulose synthesis and directs cellulose deposition in cell wall

A

microtubule, see slide 58+59
- microtubules form tracks that guide the movement of cellulose synthesizing complexes

38
Q

What are cells of animal tissue supported by

A

cytoskeleton, held together by cell-cell junctions and extracellular matrix (thats secreted by the cell themselves)

39
Q

What is the biggest feature of connective tissue and what does it help with?

A

extracellular matrix , provides mechanical support for cells in animal connective tissue

39
Q

What is the strength of animal connective tissue provided by…. (a protein)

A

a protein called collagen (cable-like)

40
Q

types of connective tissue

A
  • tendons, dermis of skin
  • bone, cartilage
  • adipose (fat)
  • aqueous humor of eye
41
Q

What does the Derivative amino acids of collagen (protein of the extracellular matrix in animal connective tissue) must undergo to make collagen function? (2)

A

hydroxylation of proline and lysine creates
- hydroxy proline
- hydroxy lysine

(with the help of ascorbic acid as a cofactor)

42
Q

Characteristics/structure of Proteoglycans, where can it be found

A
  • proteins that are heavily glycosylated , containing core proteins called glycosaminoglycans (GAGs)
  • GAGs are made of repeating disacchardie subunits ( chondroitin surface, keratan sulfate, hyaluronate)
  • attracts water to provide a porous, hydrated gel
  • fill spaces between cells in the extracellular matrix of connective tissue
43
Q

Functions of Proteoglycans

A
  • resists compression
  • forms pores of varying sizes for passage of molecules through ECM
  • block, encourage, guide cell migration through ECM by binding to secreted proteins
44
Q

How does the extracellular matrix connect to the cytoskeleton

A

via Integrins (integral proteins) , provides the connection to allow actin filament on the inside of the cell communicate to the outside of the plasma membrane

45
Q

What are the 4 cell-cell junctions in epithelium

A
  1. Tight junctions
  2. Adherens junctions (via actin filaments)
  3. desmosomes
  4. gap junctions
46
Q

Tight junctions in epithelium

A

FORMING SEALED COMPARTMENTS
- form barrier/seal to prevent diffusion of integral membrane proteins between apical and basolateral parts of the cell

  • forcing material to go through rather than between cells
  • this creates different membrane domains
  • consist of proteins holding adjacent epithelial cells together , ‘tight’ epithelium
47
Q

Adherens junctions in epithelial cells

A

SHAPING
- forms ‘belts’ around epithelial cells

  • adhesion belt can be tightened in selected regions of cell sheet and create invagination of epithelial sheet
  • adhesion belt is associated with actin filaments
48
Q

Desmosomes in epithelial cells

(What kind of microfilament, it’s function, any mutations)

A

STRENGTH
- anchor spots for intermediate filaments
- holds epithelial cells together
- “half” desmosomes (hemidesmosomes) anchors to epithelial layer to basement membrane (basal lamina)

49
Q

Mutations in proteins in hemidesmosomes in epithelial cells

A
  • will affect the way the epithelial anchors to the basement membrane
  • lifting of epithelial layer off basement membrane
50
Q

Gap junctions in epithelial cells

(subunits, function)

A

COMMUNICATION
- connects animal cells

  • connexon subunits
  • allows passage of very small molecules (relatively non-selective)
  • connecting cells via gap junctions allows cells to coordinate activities and work as a team
50
Q

What channel exists between plant cells , describe them

A

Plasmodesmata , they are like gap junctions in animal cells
- connect the cytoplasm of adjacent cells

51
Q

Difference between plasmodesmata in plant cells from gap junctions in animal cells

A
  • plasmodesmata are lined with plasma membrane
  • plasmodesmata can dilate significantly to permit passage
  • large macromolecules can move from nucleoplasm of one cell to the cytoplasm of distant cells
52
Q

How do cells become more specialized

A

they remember previous signals they have received

53
Q

Describe stem cells

A
  • undifferentiated cells found throughout the body that divide to provide supply types of terminally differentiated cells
  • replenish dying cells and repair damaged tissue
54
Q

Two properties of stem cells

A
  1. self renewal: ability to go through numerous cell division while maintaining the undifferentiated state
  2. multipotency: ability to generate progency of several distinct cell types
55
Q

Explain the renewal of intestinal lining

A

Epithelial migration from ‘birth’ at bottom (where cell division can be controlled) of crypt to loss at top of villus

56
Q

Where do stem cells renew themselves in animal tissue

A

in basal lamina

57
Q

Where do all blood cell types in circulation descend from

A

descends from hematopoietic stem cells
- its job is to replace itself and diffferentiate into major pathways
- these steps are mitotic

58
Q

Embryonic stem cells are pluripotent, what does this mean

A
  • original egg cell divides repeatedly, all containing the same genome, but are specialized in various ways
  • they express different patterns of genes/proteins

ex. early embryo can divide to become fat cell, neuron, macrophage, smooth muscle cell, gilal cells

59
Q

Are tumors cancer? What are tumors? What types of tumors are there?

A

not necessarily because cancer has tumors thatare invasive and not all are invasive, tumors are cluster of cells undergoing uncontrolled division
- Benign tumors
- Malignant tumors

60
Q

Benign tumors

A

Tumors are noninvasive and noncancerous

61
Q

Malignant tumors

A

invasive tumors that spread throughout the body via the blood or lymph to initiate secondary tumors

62
Q

describe metastasis and what tumor does this occur

A

The detachment from original tumor and invasion of other tissues when there is a loss of cell adhesion . occurs in malignant tumors

63
Q

Somatic mutation

A

any alteration of somatic cell that can give rise to cancers , affect during the development of cell

64
Q

Causes/mutations of cancer? (4)

A
  1. DNA replication and repair
  2. cell cycle checkpoints
  3. pathways that drive mitosis/cell cycle
  4. mistakes in mitosis (aneuploidy)
65
Q

General Features of Cancer Cells?

A
  • not independent on signals for growth, survival and division (ex. Ras mutation)
  • less likely to kill themselves (apoptosis)
  • can divide indefinitely (immortal)
  • genetically unstable
  • invasive (loss of cell adhesion molecules that
66
Q

How does Colorectal cancer begin

A
  • begins with the inactivation of both copies of the tumor suppressor gene APC (Adenomatous Polyposis Coli)
67
Q

What kind of cancer type is carcinoma

A

epithelial cancer

68
Q

What kind of cancer type is sarcoma

A
  • mesenchymal
    connective tissue type cancer (bone, cartilage, muscle, fat, vascular)
69
Q

What kind of cancer type is hematopoietic

A

leukemia, lymphoma
(related to red blood cells)

70
Q

Where do cancers mostly originate

A

epithelial origin

71
Q

Describe Dominant mutation

A

(gain of function)
- mutation in one copy of PROTO-ONCOGENE creates oncogene
- leads to hyperactive oncogene

72
Q

Describe Recessive mutation

A

(loss of function)
- mutation inactivates one copy of tumor suppressor gene
- second mutation inactivates second gene copy
- results in complete loss of tunor suppressor gene activity

73
Q

Assuming no ethical limitations. organoids resembling mammalian tissues/organs can be derived by culturing ____________ under the appropriate conditions.

A
  • cells from very early embryos
  • adult stem cells obtained from organs such as liver and pancreas.
  • reprogrammed (de-differentiated) adult cells such as skin fibroblasts.
74
Q

The transport of vesicles of secretory product to the plasma membrane requires …

A

microtubules, kinesin, ATP

75
Q

Which type of cytoskeletal component would help reinforce the effectiveness of desmosomes in epithelial cells?

A

keratins

76
Q

What is the most abundant protein within animal cells?

A

actin

77
Q

What is a major difference in the extracellular matrix (ECM) of animal cells and plant cell walls?

A

The plant cell wall is primarily carbohydrate, whereas animal ECM is mostly protein based, with some carbohydrate.

Term 1 (21 decks)

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