Lecture 3: Cell Adhesion

Question 1

Fill in the blank.

__________ is essential for multicellular organisms

Answer 1

Cell cohesion

Question 2

Cell Cohesion

Answer 2

how cells stick together

Question 3

Starting from the outside of the cell, what are the tissue layers of cells

Answer 3

epithelial tissue: lines surfaces, cavities, and organs

basil lamina: can be included in epithelial tissue

connective tissue

collagen fibers

Question 4

what is the difference between epithelial and connective tissue

Answer 4

in epithelial tissue, cells are directly connected to each other with minimal extracellular matrix whereas in connective tissue cells are dispersed through the extra cellular matrix

Question 5

why are epithelial cells polarized?

Answer 5

because each cell surface must be different to perform different functions

Question 6

What do epithelial structure and function require

Answer 6

junctional complexes

Question 7

starting from the apical side (the top) to basil what junctions do mature epithelial cells have?

Answer 7

tight junctions: seal gaps between epithelial cells forming sealing strands

adherens junction: connect actin filament bundles in one cell with the next- forming adhesion belts

desmosomes: connect intermediate filaments in one cell to those of the next, these exist at specific points in the cell

gap junctions: allow the passage of small water soluble molecules from cell to cell- these do not go to the outside

actin-linked cell-matrix junction: anchors actin filaments in cell to extracellular matrix

hemidesmosomes: anchors intermediate filaments in cell to extracellular matrix

Question 8

what usually mediates cell-cell junctions

Answer 8

cadherins

Question 9

cadherins

Answer 9

type of adherin junctions. they are transmembrane proteins expressed by both cells

Question 10

what are cell-extracellular matrix junctions mediated by?

Answer 10

integrins

Question 11

Fill in the blank.

cadherins mediate cell-cell connections at _____

Answer 11

adheren junctions

Question 12

how do cadherin domains interact with each other

Answer 12

their homophilic domains interact in the extracellular domains and it is their N termini that interact

Question 13

what do cadherin interactions require? why?

Answer 13

they require Calcium because it makes it rigid so that they can stick to each other

Question 14

Can different types of cadherins interact with one another? IF they cannot what is the significance of this specificity

Answer 14

No cadherins can only undergo homophilic interactions between cells expressing the same type of cadherins and this is significant because it is a way for cells to sort into groups

Question 15

How does cell adhesion and actin mediate morphogenesis

Answer 15

In an epithelial cell, adhesion belts can line the epithelial cell and energy tightening where actin starts to squeeze together causing invagination

Question 16

What tells the body do to ensure proper neural tube closure

Answer 16

Cells contain different types of cadherins and hemophiliac cadherins will join together to ensure neural tube closure

Question 17

What role as tight junctions play in the body

Answer 17

They act as guards to keep stuff separate and define domains

Question 18

Apical domain

Answer 18

Face cavity, surface, and /or organs

Question 19

Basal domain

Answer 19

Face the inside of the body

Question 20

What forms tight junctions

Answer 20

Occludin and claudins

Question 21

Why are tight junctions important in the body

Answer 21

Because they limit diffusion into the extracellular space to prevent membrane proteins from moving between apical and Basel domains. This is an important step in limiting what enters the cell

Question 22

In glucose transport, where are active transporters located?

Answer 22

They remain on the apical domain, on the lumen of the gut

Question 23

Describe the movement of glucose through the gut in terms of concentration levels

Answer 23

Glucose moves across gut lumen from a low concentration to the blood, with a high concentration to

Question 24

What is needed to pump glucose against its concentration gradient from a low to high concentration

Answer 24

It requires an energy source from sodium moving from high to low concentration

Question 25

how do passive carriers assist glucose move across cells

Answer 25

Passive carriers on the basalateral side also glucose to diffuse out of theepithellal cell to the tissue/blood

Question 26

How as tight junctions help ensure that this glucose transport system works

Answer 26

By keeping the transporters in the right domains

Question 27

integrin heterodimers

Answer 27

Mediate cell-cell matrix junctions

Question 28

What do integrin heterodimers interact directly with

Answer 28

Extracellular matrix proteins

Question 29

What is the significance of integrin-actin interactions in the cell

Answer 29

Provide the adhesion necessary for cell migration

Question 30

What role does cell-matrix junctions have in epithelial tissue? connective tissue?

Answer 30

In epithelial tissue, they provide adhesion to the basil Lamina extracellular matrix.in n connective tissues, they provide cell interaction with extracellular matrix and movement

Question 31

What are the first junctions to form? Why?

Answer 31

Adhesion junctions form first because they are sticky so everything binds together and they are able to define the apical and basil domains by providing polarity cues.

Question 32

Describe an example where adherin junctions set up the apical and basil domains

Answer 32

Adhering junctions active crumbs and par complex that are responsible for making apical side. Scribble will inhibit par and make the other side basil while par will inhibit Scribble to continue making the apical side

Question 33

What are the 3 main components in cell polarity to define a mature epithelium

Answer 33

Intracellular trafficking (right proteins on right side), cytoskeleton organization (right compartments on right side), and cell adhesion (ability for cells to stick)