ECM etc

Question 1

what mediates swimming and crawling of cell?

Answer 1

swimming : mediated by microtubules e.g.. cilia and flagella

crawling : actin microfilaments

Question 2

Axoneme and structure ?

Answer 2

central strand of cilia and flagella, microtubules arrange in a 9 pairs around 2 centrals. Radial spokes like all together

Question 3

Basal body?

Answer 3

links cytoskeleton to the axoneme with a 9x3 array and much smaller. has a transition zone between

Question 4

How come the 9 doublets have polarity?

Answer 4

A fibre has 13 protofilimetns

B fibre has 10

Question 5

Dynein arms?

Answer 5

2 linkers between each pair,ATP dependent, produced a sliding motion causing them the bend and flex

Question 6

Difference between actin and myosin?

Answer 6

actin is thinner and lighter

myosin has globular heads and a coil of 2 alpha helix

Question 7

What is Amoeboid movement?

Answer 7

most common in eukaryotes
protrusion of cytoplasm forms a pseudopodia, membrane detaches from the actin and hydrostatic pressure causes it to bleb out. fRONT OF CELL PUSHES FORWARD AND MAKES NEW adhesions with the ECM by interns. original adhesions are lost as these are stronger and cell moves forward

Question 8

Role of the ECM

Answer 8

regulated migration, tisue integrity, cell shaped anchorage for cell proliferation

Question 9

Collagen?

Answer 9

triple alpha helix, most common ECM component, able to self assemble, proline glycine rich and produced by fibroblasts and epithelial cells. hydroxylation causes crossing over

Question 10

Defects in collagen?

Answer 10

Ehlers danios syndrom - no tensile strength in skin so tears easily, arthritis too and arterial rupture

Scurvy - if no vitamin C then no hydroxylation that causes collagen to cross over

Question 11

Elastin?

Answer 11

laid down over a microfibril scaffold, by linking small tropoelastin together. requires a high amount of energy to overcome barrier

Question 12

What is laminin?

Answer 12

signalling roles, a trimeric protein made of differs alpha beta gamma chains, has globular heads. interact with cells that have a laminin binding domain

Question 13

Fibronectin?

Answer 13

fibrous protein, s-s bonds, cross links with self. Repeated RGD (arginine, glycine, aspartic acid) sequence allows it to adhere to ECM

Question 14

Tight junctions?

Answer 14

barrier between lumen and vessel. seal gaps between epithelial cells, prevent fluid flowing across membranes, claudin and occludin form at junction and segregates membrane giving the cell polarity so e.g.. cholesterol only on apical side

Question 15

Adherence junctions?

Answer 15

cell - cell junctions clustered by actin, cadherins anchor to the cytoskeleton forming interactions, drive contractions. are calcium dependent. connects actin bundle in one cell to the bundle in the other, strong

Question 16

Gap junctions?

Answer 16

communicating junctions made of 6 subunits of connexions , pass back and forth e.g. in neurones. Na+ and K+, monosacharides, H2O ATP. need to be close e.g. within 2-4nm

Question 17

sugars

Answer 17

diasacheride units most associated with protines eg. GAGs, proteoglycans by a covalent link

Question 18

hyaluronic acid

Answer 18

big charged molecule draws h20 in so used as a lubricant to inject into bones help with arthritis

Question 19

integrin?

Answer 19

attatches cell to ECM. heterodimer with alpha and beta submit. if B1 defect embryo dies at implantation if alpha 5 defect survives till mesoderm development then dies

Question 20

glanzmanns thrombasthemia

Answer 20

bleeding disorder due to defects of intern on platelets which usually help blood clot

Question 21

desmosomes

Answer 21

keratin filaments anchored to cytoplasmic plaque. cadherins and intermediate filaments. not contractile but provide strength e.g in heart and epidermis

Question 22

hemidesmosomes

Answer 22

connect cells to the basal lamina

Question 23

pemiphigus

Answer 23

autoimmune disease attacks cadherin family member called desmoglien found in desmosomes so causes skin blistering

Question 24

selectins ?

Answer 24

bind to sugars on leukocytes causing them to slow then arrest so form adhesions so leukocyte moves into the tissue from blood