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Cells to Organisms 2 > Cell Adhesion 1 - intro lecture > Flashcards

Cell Adhesion 1 - intro lecture Flashcards

1
Q

what is the definition of a tissue?

A

a cooperative assembly of cells and extracellular matrix woven together to form a multicellular matrix woven together to form a multicellular fabric with a distinctive function

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2
Q

what is the cell theory and who proposed it?

A
  • cells are the building blocks of life
  • Schleiden and Schwann 1839
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3
Q

Explain stress transmission in multicellular organisms

A
  • to make large and stable structures they need a way to transmit physical stress.
  • two strategies of doing this
  • Extracellular matrix (ECM) - plant and animal cells
  • Cytoskeleton and cell-cell adhesions that connect the cytoskeletons of neighbouring cells - animal cells
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4
Q

Explain the primary cell wall in plant cells

A
  • thin and flexible so they can expand as the cell growth
  • middle lamella - has a lot of pectin. Cements cell walls of adjacent cells
  • cellulose microfibrils - tensile strength
  • pectin - fill spaces between cellulose, resistance to compression
  • crosslinking polysaccharides - crosslink the cellulose microfibrils
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5
Q

What is the primary growing force of the plant cell?

A

Turgor pressure

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6
Q

What causes the secondary cell wall to form?

A
  • cells have stopped growing
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7
Q

How does the secondary cell wall form?

A
  • making the primary cell wall thicker or making a new one with a different composition
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8
Q

What is the most abundant macromolecule?

A

cellulose

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9
Q

What is the role of cellulose microfibrils in plant cell walls?

A
  • give the cell wall tensile strength
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10
Q

What is a cellulose microfibril made from?

A
  • 18 cellulose molecules connected by hydrogen bonds
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11
Q

What is a cellulose molecule made from?

A
  • unbranched chains of glucose
  • each glucose is alternatively inverted - neighbours are always in different orientations
  • beta 1- 4 glycosidic bond
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12
Q

explain the structure of pectin

A
  • alpha 1 - 4 glycosidic linkage between D-galacturonic acid units
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13
Q

explain the function of pectin in plant cell walls

A
  • hydrated and binds cations
  • space filling similar to glycosaminoglycans in animal ECM
  • resists compression
  • crosslinks with cellulose to form a matrix
  • common in primary cell walls
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14
Q

Explain the structure of wood

A
  • when a cell dies its wall stays, forming the channels
  • contains lots of lignin which has a high strength when wet
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15
Q

What is the structure of lignin

A

A complex polymer of cross linked phenolic compounds

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16
Q

Explain the general structure of plant cell walls

A
  • main structural components - polysaccharides (made from CO2 and H2O)
  • some proteins for remodelling during growth, not as much as animals
17
Q

Explain the orientation of cellulose microfibrils in plant cell walls

A
  • horizontal - cell is more likely to grow in girth
  • vertical - cell is more likely to grow in length

Cells elongate perpendicular to cellulose microfibrile orientation

18
Q

Explain cellulose synthesis

A
  • under the plasma membrane there are microtubules aligned with cellulose microfibrils
  • microtubules help direct cellulose
  • cellulose synthase complex connected to microtubules underneath
  • microtubules guide enzyme complexes, determining the direction that cellulose is synthesised in (vertical or horizontal)
19
Q

What is the ECM?

A
  • extracellular matrix
  • proteins and other molecules outwith the cell that give the cell support
20
Q

Describe the structure of connective tissue

A
  • lots of ECM - bears mechanical stress
21
Q

Describe the structure of epithelial tissue

A
  • less ECM - cytoskeleton carries mechanical stress
22
Q

Give 5 places you would find connective tissues

A
  • bone
  • cartilage
  • tendon
  • skin
  • vitreous humour
23
Q

Describe the structure of bone

A
  • osteoblasts (bone forming cells) secrete collagen matrix
  • Ca, Mg and phosphate ions join matrix - forms hydroxyapitite
  • hydroxyapitite - hard but not brittle so still flexible
  • Osteons - concentric rings around central canal containing blood vessels and nerves
  • bone doesn’t have much cells
24
Q

Explain the structure of cartilage

A
  • strong and flexible
  • absorbs impact without breaking
  • lots of ECM (collagen and proteoglycan (chondroitin sulphate)
  • no mineralisation
25
Q

Explain the structure of the vitreous humour

A
  • in lens and retina
  • clear viscous gel made of water, collagen and hyaluronic acid
  • basically no cells
  • doesn’t appear in tissue sections and H&E
26
Q

Explain the structure of collagen

A
  • tripple strand helix of collagen strands- long and stiff
27
Q

Explain the structure of collagen fibrils

A
  • triple collagen molecules that have assembled together to form
28
Q

What are some different forms of collagen?

A
  • triple woven
  • fibrils
  • fibers
  • sit on surface of fibrils and hold them together and connect them to other components of the ECM
29
Q

What is a collagen fibre?

A
  • collagen fibrils which have joined together to form fibres
30
Q

Where is collagen most common?

A
  • bone
  • tendon
  • skin
31
Q

What produces collagen?

A

fibroblasts

32
Q

Explain the collagen fibril arrangement in skin

A
  • plywood pattern
  • allows skin to resist tensile stress in many directions
33
Q

Explain collagen fibril arrangement in tendons

A
  • tendons attach muscle to bone
  • collagen fibres arrange parallel along the axis of tendon extension
34
Q

What are fibroblasts?

A

cells that form collagen

35
Q

how do fibroblasts work?

A
  • produce and shape collagen
  • if there is a gap between tissues, fibroblasts will connect it by controlling the formation of collagen
  • useful in healing woulds and in the formation of tendons
36
Q

What is the effect of incorrect collagen assembly?

A
  • cause skin to be hypterextensible
  • Ehlers-Danlos syndrome (EDS) is caused by mutation in genes that code for collagen and proteins involved in collagen assembly
37
Q

Explain collagen precursors

A
  • collagen secreted in precursor form
  • peptide extensions to stop premature fibril assembly
  • precursors cleaved by pro collagen protease to form mature collagen outside of the cel
  • secreted by exocytosis where they then form large aggregates, would be harmful inside the cell
38
Q

What is the role of procollagen protease?

A

cleave collagen precursors to form mature collagen outside of the cell

Cells to Organisms 2 (4 decks)

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