Cell adhesion and communication Flashcards
What do unicellular organisms there to ?
Surfaces or food
- no permanent connection with other cells even tho in colonies
What is planktonic and sessile?
Planktonic = freely exist in medium Sessile = attached to surface/ biofilm e.g agar
What is the extracellular matrix?
- material produced by cells and secreted into surrounding medium
- non- cellular
- arthropods produce chitin
- role in tissue development, function and disease
What are the mechanical roles of the ECM?
tensile + compressive strength
Elasticity
What are the protection roles of Ecm ?
buffer from extracellular change (pH)
Retention of water
What are the organisational roles of ECM?
bind growth factors and interact with cell-surface receptors
Describe connective tissue features
low cell density abundent in ECM ECM load bearing Cell attachments to ECM = force transmission in bones and tendons
Describe epithelial tissue features
closely bound into epithelial sheets
Gut lining and skin epidermis
How does specialisation occur?
highly mineralised in bone + teeth
Transparent in cornea
Elastin in tendons
Liquid in blood plasma
Describe the structure of cellulose
Glucose polymer
1-4 linkage
cellulose strands for in cell mem via cellulose synthase rosettes
Describe the structure of hemicellulose
cross link cellulose microfibrils
backbone = glucose residues (glycosylated)
What contributes to the jell like structure of the matrix?
pectin polysaccharides
What regulates the fluidity of the ECM?
calcium abundance - more ca - more cross links - stiffer
Methylation prevents crosslinks - more fluid
What does pectin methylesterase (PME) do?
Demethylase pectin via ca++ bridges
Why are bacterial ECM different?
its a capsule composed of high molecular weight polysaccharides
What are the three types if cell junctions?
Occluding
Anchoring
Communicating
What are the main roles of the 3 cell junctions?
Occluding = impermeable barrier Anchoring = mechanical support (attachment) Communicating = exchange of chemical/electrical info between cells
Why do epithelial cells need tight junctions ?
they are polar
What cells secrete matrix macromolecules ?
fibroblast cells
What cells form bone ?
Osteoblasts
what cells from cartilage ?
Chondroblasts
What are the properties of GAGs ?
acidic
-ve = na + attracted to them = attracts water so gel forms = BULKING AGENT
compressive strength
Metabolically cheap
How are GAGs bonded to proteoglycans ?
Covalently
What are proteoglycans ?
a serine rich protein decorated with hundreds of O linked acidic, sulphated GAGs
How does the ECM contribute to cell growth ?
Bind chemokines at inflammatory sites (prolonging WBC attracting activity) Block certain proteins Oligomerises FGF (fibroblast growth factor) = easier binding to its tyrosine-kinase receptor
Why does the lack of vitamin c weaken collagen?
Unhydroxylated collagen is destroyed
Vit C is the cofactor for proline hydroxylase which forms hydroxyproline post translationally
What do the types of collagen do?
I - skin, bones, tendons
II - Cartilage
IX and XII- flexible and link type I and II
IV and VII - Mesh structure around the basal lamina
What does the basal lamina do ?
Adds polarity
Separates epithelial sheets, fat or muscle from connective tissue
What structure does microfibrils act as a scaffold guide for ?
Elastin formation
What do cerebral organoids model?
Human brain development and microcephaly
What are organoids?
3D cellular clusters, derived from stem cells, self renewal and organisation
What are the four proteins/ molecules involved in tight junctions?
Claudin
Junction adhesion molecules (JAM)
Occludin
Zonula occluding family proteins
