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B1omed - Molecules to cells > Module 6 - Interactions between cells in multicellular systems > Flashcards

Module 6 - Interactions between cells in multicellular systems Flashcards

1
Q

Four major tissue types

A

Muscle
Nervous
Connective
Epithelia

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2
Q

The gut: the tissues comprising it and its significant features

A

Epithelia at the top (absorbing food) and bottom, connective tissue connecting epithelia and smooth muscle (for peristalsis) with nerve cells connecting as well

  • Low ECM
  • Intermediate filaments and cell-cell junctions provide strength
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3
Q

The skin: the tissues comprising it and its significant features

A

Epithelia at the top, connective tissue connecting epithelia and muscle with nerve cells connecting as well

  • Low ECM
  • Intermediate filaments and cell-cell junctions provide strength
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4
Q

Types of epithelia

A

Simple squamous (flat)
Simple cuboidal (cuboidal)
Simple columnar (columnal)
Non-keratinised stratified squamous
Keratinised stratified squamous
Pseudostratified columnar with goblet cells

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5
Q

Tight junction: what are they and what other key features do they have?

A

Seals neighbouring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them - allowing functional polarisation

  • Found in vertebrates
  • Formed from occludin and claudin proteins
  • Allow lipids in the plasma membrane to diffuse freely, but NOT membrane proteins
  • Protein composition of the apical and basal membranes can be different
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6
Q

Gap junction

A

Connexon channels (2-4nm) between adjacent cells allowing ions and small molecules (<1000 daltons) to pass through

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7
Q

Adheres junction

A

Two actin bundles joined together between neighbouring cells using cadherins

  • Forms adhesion belts (continuous bands of adheres junctions)
  • Can be contractile when myosin II interacts
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8
Q

Desmosomes

A

Intermediate filament bonding between neighbouring cells using cadherins

  • Strong tensile strength
  • Abundant in heart muscle and tough, exposed epithelia
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9
Q

Hemidesmosomes

A

Intermediate filaments anchored to the basal lamina

Integrins used

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10
Q

Types of cell connections between animal cells

A

Gap junctions
Tight junctions
Adheres junctions
Desmosomes
Hemidesmosomes

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11
Q

Plasmodesmata

A

Gap junction equivalent in plants

The only type of cell connections within plants

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12
Q

Transcytosis

A

Polarised transport of proteins from one end of the epithelia to the other

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13
Q

Cadherins

A

Transmembrane proteins in the plasma membrane which bind to an identical cadherin in the next cell

Interaction needs calcium (Ca²⁺)

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14
Q

Integrins

A

Trans-membrane proteins in the membrane that link the ECM to the cell’s cytoskeleton

Type of cytoskeleton linkage depends on context - migrating/collagen-secreting cells (focal adhesion) or epithelial monolayers (hemidesmosomes)

Protrusions adhere to the surface via:

focal contacts containing trans-membrane plasma membrane proteins called integrins

contractile actin bundles (stress fibres) attach to focal contacts

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15
Q

Protrusions and focal points

A

Protrusions adhere to the surface via:

  • Focal contacts containing trans-membrane plasma membrane proteins (integrins)
  • Contractile stress fibres (actin bundles) attached to focal contacts
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16
Q

Different types of cadherins

A

Epithelial cadherins - E-cadherins
Muscle cadherins - N-cadherins

Expressing N-cadherin instead of E-cadherin makes cells highly motile.

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17
Q

Cancer and cell-cell interactions

A

Cell-cell interactions keep cells where they should be by using specific cadherins

Specific cadherins help cells recognise each other

Cancer cells lose the specific cadherins and create tumours everywhere

Cancer cells may secrete more matrix proteases than normal, helping them to escape through the basal lamina

18
Q

Carcinomas

A

Epithelial cancer cells - these are where 85% of cancers start

19
Q

Extracellular matrix

A

Tough and flexible (skin, tendon)
Hard and dense (bone)
Shock-absorbing (cartilage)
Soft and transparent (in the eye)

20
Q

Collagen synthesis

A

Fibrous protein - a key component of connective tissue synthesised by either osteoblasts (bone) or fibroblasts (skin, tendon)

~40 different collagen genes in humans (90% of collagen mass is collagen I (key component in bones))

21
Q

Procollagen

A

The precursor to collagen, three of these single-stranded procollagen fibres are trimerised in the ER using ascorbic acid (VC) to form three-helix procollagen fibres

Procollagen only becomes collagen after cleavage outside of the cell by proteases

22
Q

SUN and KASH proteins

A

Link filaments in the cytoplasm to nuclear lamins inside the nucleus

Affects genes through alteration in response to the ECM environment

23
Q

Osteoblasts

A

Cells that deposit the ECM in bone

Calcium phosphate fills gaps

24
Q

Basal lamina

A

Laminin and collagen IV are the main components of the basal lamina

25
Q

Collagen organisation

A
  • Properly aligned in an oriented way
  • Cells rearrange fibres after secretion by pulling on them
26
Q

ECM diseases

A
  • Abnormally stretchy skin
  • Brittle bone disease
  • Skeletal disease
27
Q

Collagen linker proteins

A

Fibronectin in focal adhesions (when the cells are protruding)

Laminin in the basal lamina (keeps the cells)

28
Q

Changes in mitosis

A

Cells become rounded and less well attached to the surface while dividing

Actin and myosin filaments are drastically rearranged in mitosis, allowing cell movement

Integrins are phosphorylated and weaken their grip on the extracellular matrix

29
Q

Integrin on/off switching

A

Can be switched on and off both ways - by both intracellular signals and extracellular matrix signalling

  • When activated they take on an extended conformation
  • Microtubules do not interact with integrins (actins do)
30
Q

GAGs

A

Glucosaminoglycans: hydrophobic, large, negatively charged polysaccharides that resist compression and occupy a large volume (in comparison to their mass) - the empty spaces between cells

31
Q

Proteoglycans: what are they and how are they synthesised?

A

Extracellular proteins that have GAGs covalently linked

Protein component made in the ER, followed by glycosylation which is then completed in the Golgi apparatus and delivered to the plasma membrane by constitutive secretion

32
Q

Cartilage

A

Tough, resist compression

Used to counteract swelling pressure caused by GAGs (because they bind water molecules)

33
Q

Hyaluronan: what is it and how is it synthesised?

A

Composed only of carbohydrates, no proteins are involved in the compound

Synthesised by hyaluronan synthase at the plasma membrane and extruded directly into the extracellular space

34
Q

Plant ECM

A

Plants have no intermediate filaments so they rely on cell walls only to support their cells and give them strength and resist turgor pressure (the force exerted by the cytoplasm onto the membrane)

35
Q

Plant cell walls: primary cell walls

A

Relatively thin, allowing the cell to grow as cell expansion is driven by turgor pressure

36
Q

Plant cell walls: secondary cell walls

A

This wall has its effect specialised dependent on the location of the cell

Wood - hard and thick (crossed mesh of lignin)
Leaves - thin, flexible, and waxy

37
Q

Cellulose fibre structure

A

Polysaccharide of D-glucose containing 16 long fibres held together by hydrogen bonds

Interwoven with other polysaccharides occasionally - pectin (forms a gel that resists compression) and lignin (cross-linked mesh used for strength)

38
Q

Cellulose fibre organisation

A

Cellulose fibres resist stretching so their orientation determines the axis of growth (high cellulose concentration at the top and bottom of cells promotes lateral growth)

39
Q

Cellulose synthesis

A

Similar to hyaluronan: synthesis starts at the membrane and is made in the ER, transported into the Golgi, and then secreted out of the membrane

40
Q

Cellulose synthase complex

A

Used to organise cellulose fibres after production using microtubules in the cells as a reference

B1omed - Molecules to cells (8 decks)

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