Ubc Med Year 1 Week 4

Front 1

Define cell polarity

Back 1

positional asymmetry

Front 2

what determines cell polarity

Back 2

1. cytoskeleton
2. cell junctions

what is another name for 2.

Hint 2

adhesion complexes

Front 3

What is the cytoskeleton made of?

Back 3

1. microfilaments
2. intermediate fibers
3. microtubules

Front 4

give size, component, shape, and function of

microfilament

Back 4

5-9nm
non-covalently linked globular actin molecules
long filaments
cell adhesion, contractile force, cell shape, cell migration

Front 5

give size, component, shape, and function of

intermediate filaments

Back 5

8-12 nm
tissue specific
proteinaceous rods (most stable)
tensile strenght - esp when linked by adhesion complexes - architectural scaffold

what is the use of tissue specificity of intermediate filaments

Hint 5

can identify where a cell has come from, esp in detecting cancer metastases

Front 6

give size, component, shape, and function of

microtubules

Back 6

25nm
globular tubulin
long tubes with polarity - + and - ends
anchor for movement of motors which then move cell parts (molecules, vesicles, chromos, organelles)

Front 7

what are two categories of cell junctions

Back 7

cell-cell
cell-ecm

Front 8

What things do all junctions have in common?

Back 8

cell surface receptors
linker proteins
cytoskeletal elements

Front 9

what are cell surface receptors wrt cell junctions

Back 9

transmembrane molecules that bind to receptors on other cells or insoluble proteins in ecm (collagen)

Front 10

what are linker proteins

Back 10

cytoplasmic proteins tha tbind to the cytoplasmic tails of cell surface proteins and link to cytoskeleton

Front 11

what are the cytoskeleton elements in cell junctions for

Back 11

provide tensile strength
link to linker proteins in a scaffold manner

Front 12

what are cell-cell junction subtypes?

Back 12

1. adherens junction
2. tight junctions
3. desmosomes
4. gap junctions

Front 13

What are important components adherens junctions?

Back 13

1. adherens junction receptors
2. adherens junction linker proteins
3. cytoskeletal element

give the specific names of each...

Hint 13

1. cadherins
2. catenins
3. actin

Front 14

what functions do adherens junctions have?

Back 14

2. form a belt all the way across cell that is adhesive
2. initiate cell-cell lateral adhesion
3. tissue segregation

Front 15

what are functions of catenins?

Back 15

1. link cadherin receptors to cytoskeleton
2. act as signaling molecules when not part of junction that help regulate transcription

what is the pathological importance of 2.?

Hint 15

APC, adenomatous polyposis cancer protein down regulates this Wnt gene. When it is mutated - downregulation is ceased = over production of genes = polyps

Front 16

what is homophilic binding?

Back 16

a molecule that binds only to another molecule like itself

Why is this important?

Hint 16

basis of role of cadherins in tissue segregation during embryology

eg. N-cadherins form neural fold and E-cadherins only bind to form epithelial layer

Front 17

what molecule forms the cytoskeleton

Back 17

actin

why is this important?

Hint 17

bc means that junctions are dynamic = can form/release/reform depending on need

Front 18

What is a zonula occludens?

Back 18

tight junction
receptors bring membranes of adjacents cells close together to prevent material from leaking bw cells

Front 19

What is the main purpose of tight junctions?

Back 19

create apical and basolateral domains
- membrane proteins cannot cross this belt so limits their location

Front 20

What is the main cytoskeletal element assd with tight junctions?

Back 20

actin = so a dynamic junction

Front 21

What is the macula densa?

Back 21

desmosomes
spot welds mainly located in epithelial and muscle cells

What is a distinguishing feature in an EM?

Hint 21

a third line is visible bw the two plasma membranes

Front 22

What are gap junctions?

Back 22

channels of connexons allow for gated passage of small molecules and ions bw cells

Front 23

what cytoskeleton component is linked to desmosomes?

Back 23

intermediate filaments

Front 24

what are examples of cell-ECM junctions?

Back 24

1. hemidesmosomes
2. focal adhesions

Front 25

What junctions' receptors are heterophilic?

Back 25

hemidesmosomes and focal adhesions - they do not bind with like but with ECM

which component of ECM do they bind with?

Hint 25

laminin and collagen

Front 26

What cytoskeletal elements do hemidesmosomes attach to?

Back 26

intermediate filaments - stable and anchoring

what is a disorder of hemidesmosomes?

Hint 26

pemphigus - rare AI disorder where the epidermis blisters off the dermis

Front 27

What are stress fibers?

Back 27

actin filaments that associate with myosin

Which type of junction are they typical for?

Hint 27

focal adhesions

Front 28

How are focal adhesions' linkers distinct from other junctions?

Back 28

usually structural and enzymatic (kinases)

How does this impact the junction?

Hint 28

phosphorylation state will regulate the adhesive or contractile state of a junction

Front 29

What is the function of focal adhesions?

Back 29

often mediate cell migration - anterior and posterior ends regulated in part by focal adhesion's adhesiveness and contractility across basal/ attached surface