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MT1 Flashcards

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1
Q

what is the cytoskeleton’s function?

A

distribution/transport of organelles
mechanical strength
movement
contractile

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2
Q

what is the structure of microtubules?

A

alpha (a) and beta (b) tubulin form heterodimers, polymerise into protofilaments
13 protofilaments form microtubule

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3
Q

what is dynamic instability of microtubules and how does it occur?

A

Rapid conversion between growth and shrinkage

tubulins bind GTP, b-tubulin hydrolyses it to GDP (a-tubulin is trapped). GTP-bound ends polymerise, GDP-bound depolymerise. GDP catches up to GTP

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4
Q

what are microtubule binding proteins?

A

MAPs
modulate microtubule dynamics
MAP and Tau mutations lead to neurodegeneration

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5
Q

what is an MTOC?

A

microtubule organising centre

negative end of microtubules anchored inside, plus end grows freely out towards cytoplasm

usually a centrosome

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6
Q

what are motor proteins along microtubules?

A

kinesin -> stepwise motion. towards plus end (anterograde)
dynein -> rotational movement. towards minus end (retrograde)

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7
Q

what is the axoneme?

A

structural core of motile cilia

9 outer double microtubules, 2 central singlet microtubules

outer MTs slid by dynein relative to central MTs

when dynein moves, axonemes bend

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8
Q

what are some functions of microtubules?

A

bend axonemes
organelle transport
form mitotic spindle and pull apart chromatids in mitosis

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9
Q

what is the structure of actin filaments?

A

actin monomers assemble into filamentous actin
right handed helix, 8nm diameter
asymmetric
flexible

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10
Q

why are actin filaments polar?

A

plus end -> faster growth, barbed. has ATP binding cleft
minus end -> slower growth, pointed

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11
Q

what is treadmilling in actin?

A

ATP-actin at plus end polymerises, ADP-actin at minus end depolymerises. Equal rates, no change in shape

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12
Q

how does actin allow for cell migration?

A

protrusions form due to treadmilling, allows for crawling mechanism

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13
Q

what is the structure of intermediate filaments?

A

8 tetramer monomers wound together, multiple tetramers form filament
antiparallel
non-polar

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14
Q

what are examples of intermediate filaments?

A

keratins in epithelial cells, hair, nails
neurofilaments (light, medium, heavy) in neurons stabilise axons
nuclear laminate anchor nuclear pores and chromosomes

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15
Q

what are the different types of cell junctions?

A

tight, adherens, desmosomes, hemidesmosomes, cell-matrix

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16
Q

what are tight junctions?

A

molecular seal for intercellular space
prevent paracellular movement of ions

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17
Q

what are adherens junctions?

A

made of actin
cell:cell adhesion

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18
Q

what are desmosomes and hemidesmosomes?

A

intermediate filaments
desmosomes -> cell:cell adhesion
hemidesmosomes -> anchor cell to basement membrane, connect IMs to extracellular matrix

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19
Q

what is a cell matrix junction?

A

integrins connect extracellular matrix to actin

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20
Q

what are gap junctions and how are they formed?

A

membrane channels between adjacent cells allowing for transport of ions

connexin monomers - 6 form a connexon

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21
Q

do blood vessels supply cartilage?

A

no

cells obtain oxygen/nutrients by diffusion

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22
Q

what are the types of ossification?

A

intramembranous -> direct replacement of mesenchyme
endochondral -> cartilage model from mesenchyme forms

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23
Q

how does endochondral ossification occur?

A

cartilage model forms, growths and then calcifies. this prevents nutrients from reaching chondrocytes, so they die, leaving fragmented matrix that acts as ‘model’. osteoprogenitor cells and blood vessels invade from periosteum, proliferate into osteoblasts, which lay down bone

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24
Q

what is the diaphysis and epiphysis?

A

diaphysis -> where primary ossification centre forms. houses yellow marrow
epiphysis -> secondary ossification centre. at ends of bones. houses red marrow

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25
what is the epiphyseal growth plate?
where growth occurs resting, proliferation, hypertrophic zones fuse at the end of growth
26
what are the two types of bone?
compact and trabecular
27
what is the structure and function of compact bone type?
strength for weight bearing, resistance to bending, minimal deformation stiff, inflexible, low strain tolerance greatest in middle of shaft
28
what is the structure and function of trabecular bone type?
porous, elastic structure shock absorbers realign trabecular pattern if stress line changes, undergoes deformation
29
what is bone remodelling?
osteogenesis and osteoclasis taking place at different sites in response to mechanical loading can occur at same site to replace previous bone, maintaining bone integrity
30
what is the difference between hypertrophy and hyperplasia?
hypertrophy -> cell size increases hyperplasia -> cell number increases
31
what is gastrulation?
formation of primary germ layers: hypoblast cells replaced with endoderm, then space filled by mesoderm. epiblast becomes ectoderm
32
what are the checkpoints of cell division?
entry into s-phase -> commits cells to cycle dna -> quality check, triggers entry into mitosis spindle -> if chromatids are ready for separation, triggers entry into anaphase
33
what are cyclins and CDKs?
cyclins bind to and activate cyclin dependent kinases, regulate the cell cycle S-cyclin must be abundant for cell cycle to continue
34
what are the functions of connective tissue?
mechanical, metabolic, defence, repair, growth
35
what are the types of connective tissue?
loose, dense regular, dense irregular, elastic, adipose
36
what is the structure of loose connective tissue?
fibroblasts, macrophages moderate collagen, elastic and reticular fibres delicate, flexible, vascularised, not stress resistant
37
what is the function of loose connective tissue?
supports structures under pressure and low friction fills space between muscle cells, supports
38
what is the structure of dense connective tissue?
fewer cells, predominance of collagen fibres, less flexible, stress resistant irregular -> collagen in bundles, no orientation, 3D network regular -> collagen in linear orientation of fibroblasts along stress lines
39
what is the function of dense connective tissue?
resistance, protection irregular -> stress resistant in all directions (eg dermis of skin) regular -> stress resistant in one direction (eg tendon attaching striated muscle to bone)
40
what connective tissue is under the skin?
dense irregular in superficial dermis - anchors epithelium loose deeper to allow skin to move over muscle adipose in areas of fat in the loose layer
41
what is the structure and function of white adipose?
single large droplet of triglyceride fat, little cytoplasm energy storage, insulation, padding
42
what is the structure and function of brown adipose?
multiple small fat droplets, more cytoplasm, many mitochondria sympathetic innervation, heat generation
43
what is the structure of elastic tissue?
bundles of thick, parallel elastic fibres fibres of elastin associated with glycoprotein
44
what is the basement membrane and what is its function?
specialised sheet of extracellular matrix proteins and GAGs associated with epithelial layers, muscle cells, blood vessels cell adhesion, cell organisation, diffusion barrier
45
what cells are in loose connective tissue?
fibroblasts, macrophages, mast cells, leukocytes
46
what are fibroblasts?
secrete most extracellular matrix molecules lays down fibres in particular orientation
47
what are macrophages?
tissue phagocytes initiate and down regulate inflammatory response recruit polymorphonuclear leukocytes to kill pathogens
48
what are mast cells?
secretory granules filled with bioactive molecules activated by activation of IgE receptors can phagocytose bacteria
49
what are the different types of white blood cells and what are their functions?
basophil -> release of pharmacological compounds eosinophil -> allergic and vasoactive reactions, control mast cells, inflammation neutrophil -> phagocytosis
50
how do neutrophils migrate to an area of inflammation?
intercellular cell adhesion molecule binds to integrin on neutrophil membrane
51
what is the extracellular matrix and what makes it up?
scaffold, active regulation of cells, determines tissue physical properties made up of fibrous proteins and glycosaminoglycan (highly hydrated, gel-like ‘ground substance’)
52
what fibres make up the connective tissue?
collagen fibres, reticular fibres, elastic fibres
53
what is the structure of collagen?
string of repeated glycine-containing motifs. 3 chains assemble end-to-end and staggered to form collagen fibrils, then fibres in triple helix glycine used as it is the only amino acid small enough to fit inside the triple helix crowded interior
54
what diseases are related to collagen?
Ehlers-Danos osteogenesis imperfecta scurvy
55
what is the structure and function of reticular fibres?
reticulin - fibres of type 3 collagen short, thin fibres form mesh work holding tissue elements together in haemopoietic tissue
56
what is the structure of elastic fibres?
elastin core (coiled polypeptide chains of tropoelastin) cross linked covalently to form 3D mesh work, with fibrillin on surface (micro fibrils of glycoprotein). elastin fibres can branch, stretch and recoil in lung, skin and blood vessel walls
57
what disease is linked to elastic fibres?
Marfan’s Syndrome
58
what is a glycosaminoglycan?
long, unbranched polysaccharide chains highly anionic attract sodium and water, form porous hydrated gels
59
what is a proteoglycan?
GAGs covalently attached to proteins form gels of varying pore size: molecular sieves resist mechanical compression forces
60
what makes up the ‘ground substance’?
GAGs proteoglycans polysaccharides
61
what are caspases used for?
apoptosis
62
what is a paracrine ligand?
secretes a signal to change nearby cell behaviour diffusable
63
what is a juxtacrine ligand?
ligand on one cell binds to a receptor on an adjacent cell. present in gap junctions
64
what is mosaic development?
fate of a cell is determined before or during fertilisation
65
what are the types of muscle?
smooth and striated

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