Cell adhesion and communication

Question 1

What do unicellular organisms there to ?

Answer 1

Surfaces or food

- no permanent connection with other cells even tho in colonies

Question 2

What is planktonic and sessile?

Answer 2

Planktonic = freely exist in medium 
Sessile = attached to surface/ biofilm e.g agar

Question 3

What is the extracellular matrix?

Answer 3

• material produced by cells and secreted into surrounding medium
• non- cellular
• arthropods produce chitin
• role in tissue development, function and disease

Question 4

What are the mechanical roles of the ECM?

Answer 4

tensile + compressive strength

Elasticity

Question 5

What are the protection roles of Ecm ?

Answer 5

buffer from extracellular change (pH)

Retention of water

Question 6

What are the organisational roles of ECM?

Answer 6

bind growth factors and interact with cell-surface receptors

Question 7

Describe connective tissue features

Answer 7

low cell density 
abundent in ECM
ECM load bearing 
Cell attachments to ECM = force transmission 
in bones and tendons

Question 8

Describe epithelial tissue features

Answer 8

closely bound into epithelial sheets

Gut lining and skin epidermis

Question 9

How does specialisation occur?

Answer 9

highly mineralised in bone + teeth
Transparent in cornea
Elastin in tendons
Liquid in blood plasma

Question 10

Describe the structure of cellulose

Answer 10

Glucose polymer
1-4 linkage
cellulose strands for in cell mem via cellulose synthase rosettes

Question 11

Describe the structure of hemicellulose

Answer 11

cross link cellulose microfibrils

backbone = glucose residues (glycosylated)

Question 12

What contributes to the jell like structure of the matrix?

Answer 12

pectin polysaccharides

Question 13

What regulates the fluidity of the ECM?

Answer 13

calcium abundance - more ca - more cross links - stiffer

Methylation prevents crosslinks - more fluid

Question 14

What does pectin methylesterase (PME) do?

Answer 14

Demethylase pectin via ca++ bridges

Question 15

Why are bacterial ECM different?

Answer 15

its a capsule composed of high molecular weight polysaccharides

Question 16

What are the three types if cell junctions?

Answer 16

Occluding
Anchoring
Communicating

Question 17

What are the main roles of the 3 cell junctions?

Answer 17

Occluding = impermeable barrier 
Anchoring = mechanical support (attachment)
Communicating = exchange of chemical/electrical info between cells

Question 18

Why do epithelial cells need tight junctions ?

Answer 18

they are polar

Question 19

What cells secrete matrix macromolecules ?

Answer 19

fibroblast cells

Question 20

What cells form bone ?

Answer 20

Osteoblasts

Question 21

what cells from cartilage ?

Answer 21

Chondroblasts

Question 22

What are the properties of GAGs ?

Answer 22

acidic
-ve = na + attracted to them = attracts water so gel forms = BULKING AGENT
compressive strength
Metabolically cheap

Question 23

How are GAGs bonded to proteoglycans ?

Answer 23

Covalently

Question 24

What are proteoglycans ?

Answer 24

a serine rich protein decorated with hundreds of O linked acidic, sulphated GAGs

Question 25

How does the ECM contribute to cell growth ?

Answer 25

``` Bind chemokines at inflammatory sites (prolonging WBC attracting activity) Block certain proteins Oligomerises FGF (fibroblast growth factor) = easier binding to its tyrosine-kinase receptor ```

Question 26

Why does the lack of vitamin c weaken collagen?

Answer 26

Unhydroxylated collagen is destroyed | Vit C is the cofactor for proline hydroxylase which forms hydroxyproline post translationally

Question 27

What do the types of collagen do?

Answer 27

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

Question 28

What does the basal lamina do ?

Answer 28

Adds polarity | Separates epithelial sheets, fat or muscle from connective tissue

Question 29

What structure does microfibrils act as a scaffold guide for ?

Answer 29

Elastin formation

Question 30

What do cerebral organoids model?

Answer 30

Human brain development and microcephaly

Question 31

What are organoids?

Answer 31

3D cellular clusters, derived from stem cells, self renewal and organisation

Question 32

What are the four proteins/ molecules involved in tight junctions?

Answer 32

Claudin Junction adhesion molecules (JAM) Occludin Zonula occluding family proteins