CBG 29

Question 1

what are the 3 types of physical communicating junctions?

Answer 1

GAP(electrical)
protein-protein (semaphorin)
plasmodesmata

Question 2

what are the 2 types of anchoring non communicating junctions?

Answer 2

Adherens and desmosomes

Question 3

are tight junctions non communicating?

Answer 3

yes

Question 4

Neuromuscular junction and chemical synapses

Answer 4

nerve terminal in longitudinal depression in surface of muscle fibre
depression has transverse junctional folds every 1-2uM
over each fold are active zones in presynaptic membrane
active zone=rich in vesicles
10^5 vesicles per terminal, size=50nm
synaptic cleft 30nm
NTs synthesized in terminal
post synaptic membrane is envaginated to increase sA for receptors (NT bind to receptor –> open ion channel)

Question 5

how much slower is chemical vs electrical ?

Answer 5

chemical 0.2milliseconds

electrical 50 MICRO seconds

Question 6

Tight junction

Answer 6

membranes of two cells join to form impermeable barrier to fluid

hold cells together,barrier function (transport and osmotic balance), in blood-brain stops signals reaching brain.affects cell polarity
leaky epthelial--> PCT
tight epithelial(tight junction)-DCT

24 claudins in humans,
claudin 20kda
occludin 65kDa (522 aa polypeptide)
and zo-1 anchor strands to actin and is on intracellular side of plasma membrane

Question 7

Desomosome

Answer 7

stop shearing forces, diameter
demoglein and desmocollin=extracellular domain
attachment plaque-desmoplakin and plakoglo0bins
has cadherin as adhesion molecule
mutations cause ARRHYTHMOGENIC CARDIOMYPATHY

Blistering diseases PEMPHIGUS -antibodies target desmogene,desmode breakdown,fluid through epithelium.

Question 8

Adherens

Answer 8

cytoplasmic face linked to actin cytoskeleton

morphogenesis and remodelling of tissues and organs

more basal than tight functions
physically link cells
regulate cell-cell contact (actin)

major proteins=-cadherins and catenin(plakoglobin)

Question 9

Plasmodesmata

Answer 9

primary-cell division
secondary-mature clls
cell walls=apoplast,small soluble proteins through
plasmodesmatat=sympastic direct regulated pathway
cytoplasmic sleeve-permeable to small ions and sugars
Callose-olysacchariseat neck of sleeve,more Ca smallr pores,less permeability
Desmotubule-runs through cytoplasmic sleeve
each lant cell–> 10^5 plasmodesamta
which is 1-10um and 50nm in diameter

Question 10

semaphorins-protein protein interaction

Answer 10

ligand + receptor
semaphorin+ plexin(+neuropilin)
all have 500 aa domain
20 families 5 classes 3-7
4-6 membran associated
3-transmembran
4-proteolytically cleaved to make soluble proteins

9 mamalian plexins
4 classes A-D
all have GAP domain (affect signalling athways) and can be separated into 2 segments by Rho-GTase binding domain. RBD

controls cell contact

pathophysiology-cancer, affects bone formation + turnover, affects microvasular capillaries,autoimmun disease

Question 11

what is angigenesis?

Answer 11

formation of new blood vessels

Question 12

GAP

Answer 12

made up of 2 connexons(6 connxins each)
1 connexon is 30kda
large proteins and nucelic acids excluded
only small molecules and ions ,100KDA can pass through

control-pH and phosphorylation

pathophysiology- Deafness development
CHARCOT MARIE TOOTH DISEASE (neuropathy/neuron degen)
CARDIAC ARRYTHMIAS
skin disease.