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Cell Biology (grad) > Cell Connections > Flashcards

Cell Connections Flashcards

1
Q

*Compare how animal and plant cells support their tissues.

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2
Q

*Know the process of collagen formation and its function

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3
Q

*Describe how cells link to the extra cellular matrix

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4
Q

*Differentiate the components found in Extra-Cellular Matrix (ECM)

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5
Q

*Evaluate the various types of cellular junctions with respect to their component

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6
Q

*Understand how the components of junctions relate to their functions.

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7
Q

Describe the structure and function of plant cell walls.

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Plant cell walls are composed of polysaccharides like
1. Cellulose (primary sugar in plants), has rigid secondary walls; most abundant macromolecule
2. Pectin- in primary cell wall of growing cell (round, circles)
Plant cell wall function- provide support, LACK intermediate filaments and resist tearing and pulling force of tissues.

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8
Q

What is the most abundant macromolecule in a cell?

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Cellulose

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9
Q

Describe where plant cell walls are made and include its components like Cellulose, and synthase complex.

A

Plant cell walls are made outside the plant cells.
Cellulose is synthesized on the outer surface of the cell.
Cellulose synthase complex travels along microtubules (spans PM with its portion facing externally and microtubule anchoring internally)
Synthase is then able to squeeze out cellulose, since PM is fluid mosaic.

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10
Q

List the 4 types of Tissues in animal cells and their funcions.

A
  1. Epithelial- forms boundaries (ex: outer surface of skin)
  2. Muscle- functions to contract
  3. Nervous- sends electrochemical signal, transmit information.
  4. Connective- cells form ECM (extra-cellular matrix)
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11
Q

What structures make collagen? How does collagen become collagen fiber.

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Fibroblasts make collagen fibers.
Mammalian cells has over 20 types of collagen
Collagen (like intermediate filaments) RESIST STRETCHING.
Formation order:
1 collagen molecule (triple-stranded) will become one main collagen fibril and form a collagen fiber
(Collagen molecule to collagen fibril to collagen fiber (smallest to largest group)

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12
Q

What kind of tissue is collagen a huge component of?

A

Connective tissue.

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13
Q

Describe the process of Collagen formation.

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Collagen formation:
1. initial collagen will be procollagen that forms.
2. The procollagen will then be excreted out and have terminal procollagen extensions.
3. Procollagen proteinases will cleave terminal extensions or ends, leaving only collagen molecule
4. Collagen molecule will then self-assemble into fibrils (Spontaneously)
procollagen ends can only be cleaved once outside.

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14
Q

Describe the pathology associated with collagen defects.

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people with collagen defects can develop:
Ehlers-Danlos Syndrome- genetic defect in collagen or procollagen proteinases.
This INCREASED stretchiness of skin (able to resist pulling)

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15
Q

Describe collagen organization and its different components and examples.

A

Collagen organization is dependent on tissue
- Tendons- organize collagen in parallel sheets (to resist a lot of tension and pulling
tendon fcn: (anchor muscle to bone)
-Skin- wicker-like pattern
Fibroblasts organize the fibers they secrete.

Tendons and ligament composed primarily of collagen.
When depositing new collagen, get breaking, uneven pattern- stretch marks.

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16
Q

What are the collagen collectors that connect collagen to extracellular matrix?

A

Fibronectin is a collagen connector.
fibronectin is an extracellular protein, that binds to collagen fibers, and changes confirmation (hair pin shape). Fibronectin also binds to extracellular portion of INTEGRIN

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17
Q

Describe the function of integrins in the extracellular matrix.
What does integrin bind to intracellularly vs extracellularly?

A

Integrins are transmembrane proteins that ANCHOR cell to ECM (extracellular matrix).
Integrins bind to fibronectin on extracellular side
and bind to actin or cytoskeletal elements on intracellular side (to adaptor proteins)
Integrins are HETERODIMERS.

18
Q

Describe one of the two other Extracellular Matrix (ECM) molecules?

A

GAGS- Glucosaminoglycans) - sugar type of molecule in ECM of connective tissue.
-resist compression
form chains- negatively charged repeating disaccharides (- charge able to attract water)
GAGS also link to Core proteins like PROTEOGYLCANS.

19
Q

What kind of ECM molecule does cartilage have?

A

Cartilage has a lot of GAG’s that provide cushion to resist compression.
tissue with high GAGs will have a lot of water present which is important for resisting compression.

20
Q

what is the other Extracellular Matrix molecule?

A

Proteoglycans are another ECM molecule. Proteoglycans form large aggregates
-they are hydrophilic- attract water
functions:
-Guide cell migration
-influence cellular function (cell division, cancer activity)
proteoglycans use GAGS and Proteins (core proteins, link proteins)

21
Q

What are GAGS in comparison to proteoglycans?

A

GAGS are smaller building blocks of proteoglycans.

22
Q

Provide examples of GAGS and how they also serves a joint supplements.

A

GAGS can include Chondroitin sulfate, Keratan sulfate, and Hyaluronan.
These three GAGS are also joint supplements that help build up cartilage and maintain tissue.

23
Q

What are Epithelial sheets composed of and their function?

A

Epithelia:
made of multicellular sheets
-polarized- different top surface and different bottom surface
-Apical- Top surface
Basal- bottom surface
Epithelia are held together with junctions
anchored to basement membranes aka Basal lamina
Function of epithelia:
in connective tissues, they form boundaries and
specialized cells- secretion and absorption
also aid in movement of cilia; glandular epithelia- secrete mucus.

24
Q

How do you determine the type of epithelia? what are the questions one needs to ask? What can further ID the top layer of tissue?

A 
To determine types of Epithelia, you need two things: 
1. How many layers?
-one layer= simple
-multiple layer= stratified
2. what shape are the cells?
-Rectangular- Columnar
-square-shaped- cuboidal shape
-Flat-shaped- Squamous
to ID top layer of tissue, you can look at shape of nuclei( columnar- elongated ovals, round nuclei and squished my nucleus).
25
Q

Describe the polarization that occurs in epithelial sheets.

A

Epithelial sheets have a free surface (apical) on top surface that is EXPOSED.
-There is also an anchored surface (basal) called
basal lamina
In basal lamina- have type IV collagen, laminin and connective tissue.

26
Q

What are the apical modifications present in epithelia? Provide an example of a tissue with different cell types.

A

Two types of apical modifications:
1. microvilli- which increase surface area for absorption
2. Cilia- hair like structures that are see in in respiratory tract, and intestine to absorb dust, mucus and beat it up and out of lungs (sweep mucus out)
There are different cell types in a single tissue.
ex: Gut lumen: absorptive cells (microvilli) and Goblet cells (secret mucus)

27
Q

List the three types of cell junctions and their functions.

A

Cell junction Types:

  1. Tight junctions- help form boundaries (liquid cannot pass through)
  2. anchoring junctions- anchor cells to cytoskeletal elements and ECM (adhesive set–desmosomes)
  3. Gap junctions- allow for intracellular communications.
28
Q

Why are cell junctions important?

A

Cell junctions are crucial for maintenance of epithelial sheets

29
Q

Describe the functions and composition of tight junctions.

A 
Tight junctions form Water tight boundaries between cells.
-Formed by 2 proteins: 
-occludins
-Claudins
which Stitch Plasma membranes together.
30
Q

What is the role of anchoring junctions. List the three main anchoring junctions and what they anchor to

A

They anchor cells to each other and to basement membranes.
Three kinds of anchoring junctions:
1. Adherens junctions- anchor to other cells
2. Desmosomes- anchor to other cells
3. Hemidesmosomes- anchor to BASEMENT MEMBRANE

31
Q

What makes Adherens and Desmosomes unique from other anchoring junctions? What do they both utilize?

A

Adherens junctions an desmosomes utilize CADHERINS.
Cadherins bind to each other
-Homotypic bonding
-bonding requires CALCIUM
-These anchoring junctions INTRACELLULARLY bound to cytoskeleton.
-Actin- bound by adherens
-Intermediate filaments- bound by desmosomes.

32
Q

Describe how Adherens junctions work and what process they are involved in.

A

Adherens junctions anchor intracellularly to ACTIN BUNDLES. These bundles can contract and play a role in EMBRYONIC DEVELOPMENT
process of embryonic development:
-invagination of epithelia sheet caused by tightening of adhesion belts in regions in cells sheet
-then epithelial tube pinches off from overlying sheet of cells
-forms epithelial tube or vesicle

33
Q

What kind of things do anchoring junctions like adherens junctions form.

A

Anchoring junctions aid in embryonic development through Neural tube formation and Eye cup formation.

34
Q

What type of pathological condition can result if neural tube fails to fold?

A

If neural tube fails to fold, it can cause spina bifida, due to lack of folic acid in diet of pregnant women.
spina bifida- a baby’s spinal cord fails to develop or close properly.

35
Q

What are Desmosomes and what roles do they play?

A

Desmosomes- anchoring junctions (cell to cell junctions).

  • they are anchored intracellularly to KERATIN FILAMENTs (intermediate filaments)
  • they use CADHERINS and give tensile strength.
36
Q

What are Hemidesmosomes? what kind of cell junctions are they?

A

Hemidesmosomes- junctions between cells and basal lamina

  • They are anchoring junctions
  • look like “Half a desmosome”
  • Use INTEGRINS to form junctions
  • Bind intracellularly to KERATIN filaments
  • bind Extracellularly to basal lamina.
37
Q

describe what focal adhesions are and include the structures involved. What are focal adhesions important for?

A

Focal adhesions- junctions between cells and CONNECTIVE TISSUE
-They are important for cellular migration
-Use INTEGRINS to form junctions (RBC’s, cancer cells use integrins)
Intracellular- ACTIN filaments
Extracellular- CONNECTIVE tissue.

38
Q

What is the function of gap junctions and structures involved?
What cells structures contain a lot of gap junctions?

A

Gap junctions help increase INTECELLULAR COMMUNICATION.
-They are formed by CONNEXONS
that allow the passage of:
-inorganic ions and water-soluble molecules.
They also send electrochemical signals between cells.
Cardiac tissue and intercalated discs have a lot of gap junctions.

39
Q

How do gap junction respond to signals? Provide an example

A

Gap junctions can open and close in response to various signals
For ex:
neurons labeled through gap junctions BEFORE dopamine, allow rapid transmission and dissemination
neurons injected with Dopamine- gap junctions are closed.
Calcium can also help open and close gap junctions.

40
Q

What is a plasmodesmata? What kind of cells is it seen in?

A

Plasmodesmata- plant cell versions of gap junctions
-allow for communication between cells.
formed between cell walls of adjacent plants.

41
Q

What is the chemical organization of life.

A

Molecules form tissues which form organs to Multicellular life.

42
Q

Compare and contrast the different cell junctions in terms of function and structural components.

A

-Tight junctions- form boundaries in epithelial cells, use proteins claudins and occludins to prevent liquid from passing through (seal neigboring cells together to prevent leakage).
Anchoring junctions
1. Adherens junctions- anchor to other cells; use Cadherins to bind ACTIN bundle in one cell to another bundle in adjacent cell
2. Desmosomes- anchor to other cells; use cadherins to bind to keratin filaments (INTERMEDIATE filaments)
3. Hemidesmosomes- anchor to basal membrane-use Integrins - to bind intracellularly to keratin and extracellularly to basal lamina (anchor intermediate filament to basal lamina)
-Focal adhesions-use Integrins; bind intracellularly to actin and extracellularly to connective tissue
-Gap junctions- used for intracellular communication
use connexons to allow inorganic ions, and water soluble particles pass from cell to cell
- form CHANNELS
send electrochemical signals

Cell Biology (grad) (16 decks)

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