ECM

Question 1

Lamina and fibronectins are found in soluble and insoluble forms. True or false. Why?

Answer 1

False. Fibroconectins are found in both forms, but lamina is only found in insoluble forms.

Question 2

Tight junctions are composed of networks of

Answer 2

Fibral networks that work being epithelial cells and endothelial cells

Question 3

The major structural protein of the extra cellular matrix of animal cells is

Answer 3

Collagen

Question 4

What is the purpose of GAP junctions?

Answer 4

They make it easier for small molecules to be transfered between adjacent cells.

Question 5

Mutations in Laminins and fibroconectins cause epidermolysis bullosa. True or false? Why?

Answer 5

False. It is a mutation in the collagen, from K5 and K14

Question 6

Despite the fact that they possess no intrinsic signaling ability, integrins are still considered signaling receptors. How is this possible?

Answer 6

Affinity and avidity, they are the most abundant and most critical for multicellularity to exist. They control both cell binding to ECM proteins and intracellular responses after adhesion, done with adaptor proteins linking them to signaling proteins.

Question 7

Tissue cells are connected to the extra cellular matrix by receptors that bind to the adhesive protein

Answer 7

Laminin

Question 8

Laminins and fibroconectins contain triple helical domains. True or false.

Answer 8

True. Lamina provide an adhesive substrate for cells.

Question 9

Laminins and fibroconectins contain triple helical domains. True or false

Answer 9

True. Collagen is triple but the others are double.

Question 10

What are GAP junctions?

Answer 10

They are protein structures that make it easy to directly transfer small molecules between adjacent molecules. They are found in most animal cells.

Question 11

Collagen exists as a coiled protein due to the presence of three repeating amino
Acids: __,__,__

Answer 11

Glycine, hydroxyproline, and proline

Question 12

Laminins are found primarily in the basal lámina. True or false

Answer 12

True

Question 13

Adjacent plant cells are connected via ________ to equalize the ionic concentrations of their cytosol.

Answer 13

Plasmodesmata

Question 14

Give a definition for the extra cellular matrix

Answer 14

Collection of insoluble, flexible, fibrous proteins and highly charged proteoglycan that lies outside the cellular membrane. Made by the cells themselves.

Question 15

What are the molecular connexons making by GAP junctions?

Answer 15

They have two halves, and the two halves are called connexons and hemichannels. They are made of 6 protein subunits called connexons.

Question 16

Name the location, function, and composition of hemidesmosomes in epithelial cells (6 points)

Answer 16

-They provide structural stability to epithelial sheets
-Found on basal surface of epithelial
cells
-They link the ECM to the intermediate filament network via transport receptors.
-contain transmembrane proteins
-They are linked to the intermediate filament in the cytoplasm
-They do NOT bind directly to the ECM, but indirectly, through integrin and lamina

Question 17

Explain the difference between avidity and affinity modulation of integrin receptor binding

Answer 17

Avidity: varying the clustering of receptors.
Affinity: varies the binding strength of individual receptors.

Question 18

What are hemidesmosomes? Name 5 points

Answer 18

-They provide structural stability to epithelial sheets
-They are found on the basal surface of epithelial cells, where they link the ECM to the intermediate filament network via transport receptors
-Contain transmembrane proteins (integrins, which means they can also initiate intracellular signaling pathways)
-they are linked to intermediate filament in the cytoplasm
-they do NOT bind to the ECM directly, but INDIRECTLY, through integrin and lamina.

Question 19

Recall the structure and function of integrin receptors

Answer 19

-they are two alpha and beta subunits
-Function: they act as a receptor controlling cell binding and intracellular responses after adhering
-They also function as a hook giving information about surroundings (critical for multicellularity)

Question 20

What makes elastin so elastic? Name two reasons

Answer 20

-the strength of elastic fibers arises from covalent crosslinks formed between lysine side chains in adjacent elastin monomers
-The sequence goes hydrophilic-hydrophobic-hydrophilic, which causes them to repel each other. This is when they are resting. As it elongates, it forces the subunits to come close together, and the hydrophobic/hydrophilic regions come closer together, and after the stress is released, the force spontaneously takes back its initial length.

Question 21

Name the location, function, and composition of adheren junctions in epithelial cells (6 points)

Answer 21

-link neighboring cells
-Contain transmembrane cadherin receptors
-They are a link to actin filaments
-Are involved in binding with actin filaments.
-They help Maintain two cells together
-they form strong adhesions to prevent too much passage between cells.