Passgeways from cell to cell and Basal Lamina

Question 1

What blocks passageways through gaps between cells

Answer 1

Tight junctions

Question 2

What to tight junctions prevent

Answer 2

extracellular molecules from leaking from one side of an epithelium to the other

Question 3

Name of junctional structure that bridges gaps between adjacent cells to create passageways from cytoplasm of one to another

Answer 3

Gap junctions (animals)
Plasmodesmata (plants)

Question 4

Gap junction and plasmodesmata allow neighbouring cells to exchange _______ but not _________

Answer 4

small molecules, macromolecules

Question 5

Gap junctions couple cells both ______ and ________

Answer 5

electrically, metabolically

Question 6

The gap is spanned by channel-forming proteins, of which there are two distinct families, called the _______ and the _________.

Answer 6

connexins, innexins

Question 7

Differences and similarities between connexins and innexins

Answer 7

Unrelated in sequence but similar in shape and function

Question 8

Do connexins or innexins predominate in vertebrates

Answer 8

Connexins

Question 9

Summarized explanation of channels formed by gap-junction proteins

Answer 9

The channels formed by the gap- junction proteins allow inorganic ions and other small water-soluble
molecules to pass directly from the cytoplasm of one cell to the cytoplasm of another, coupling the
cells both electrically and
metabolically.

Question 10

A gap-junction connexon is made up of

Answer 10

six transmembrane connexin subunits

Question 11

When connexons in the plasma membrane of two cells in contact are aligned, what is formed?

Answer 11

A continuous aqueous channel that connects the two cell interiors

Question 12

How is a hemichannel formed

Answer 12

when one connexon from one cell does not line up with one from another cell, instead it opens up to the extracellular space.

Question 13

What happens in regard to ions when hemichannels form

Answer 13

case ions can move into or out of the cell (depending on the concentration gradient) through this hemichannel, this essentially creates a pore

Question 14

What conformation are hemichannels generally kept in

Answer 14

Closed conformation, we want to control what goes in and out

Question 15

Why can gap junctions in different tissues have different properties

Answer 15

They are formed from different combinations of connexins, creates channels differing in permeability

Question 16

True of false: Adjacent cells expressing
different connexins cant form intracellular channels

Answer 16

False, they can.

Question 17

What mutation is the most common of all genetic causes of congenital deafness and how does it do that

Answer 17

Connexin-26
-Death in the organ of Corti through the disruption of the flow of ions in the organ’s sensory epithelium

Question 18

Can cells regulate the permeability of their gap junctions

Answer 18

Yes

Question 19

Gap-junction channels close when

Answer 19

a cell’s plasma membrane is damaged causing ions to leak in

Question 20

What happens when gap-junction channels close due to damaged PM

Answer 20

Isolates the cell, prevents its neighbors from harm

Question 21

What neurotransmitter reduced gap-junction communications between a class of neurons in retina in response to increase in light intensity

Answer 21

Dopamine

Question 22

What does dopamine do in retina

Answer 22

reduces gap-junction communication between a class of neurons in the retina in response to an increase in light intensity

Question 23

What does the reduction in retina gap-junction permeability do

Answer 23

Helps retina switch from using rod receptors to cone receptors, detects color and fine detail in bright light

Question 24

The matrix is composed of various _____ and _____

Answer 24

proteins and polysaccharides

Question 25

Proteins and polysaccharides (that make up matrix) are secreted

Answer 25

locally

Question 26

In our own bodies, the most plentiful forms of extracellular matrix are found in

Answer 26

bulky connective tissues such as bone, tendon, and the dermal layer of the skin

Question 27

Basal lamina is also referred to as the

Answer 27

basement membrane

Question 28

The basal lamina surrounds what cells (3)

Answer 28

Muscle cells, fat cells and Schwann cells

Question 29

True or false: the basal lamina is a type of ECM

Answer 29

True

Question 30

Basal lamina differences in muscle vs epithelium cells

Answer 30

Muscle: -basal lamina wraps around cell, following striated muscle path -basal lamina surrounded by connective tissues Epithelium: -more polar -sheath of villi on one polar (apical), basal attached to basal lamina, connective tissue under

Question 31

Functions of the basal lamina

Answer 31

-Determines cell polarity -Influences cell metabolism -Organize the proteins in adjacent PM -Promotes cell survival, proliferation, and differentiation

Question 32

In the skin, the epithelial outer layer (epidermis) depends on the strength of the ____ to keep it attached to underlying connective tissue (dermis)

Answer 32

Basal lamina

Question 33

Defects in certain basal lamina proteins cause the epidermis to

Answer 33

Become detached from the dermis

Question 34

What is the primary component of the basal lamina

Answer 34

Laminin

Question 35

The basal lamina is synthesized by the cells on each side of it,which are:

Answer 35

Epithelial cells and cells underlying the bed of connective tissue (stroma)

Question 36

2 main classes of basal lamina

Answer 36

Fibrous proteins (glycoproteins with short oligosaccharide side chains) and polysaccharide chains of the type called glycosaminogylcans (GAG), linked covalently to specific core proteins to form proteoglycans

Question 37

Basal lamina composition varies between tissues but typically contains the glycoproteins:

Answer 37

laminin, type IV collagen, and nidogen along with the proteoglycan perlecan

Question 38

Basal lamina is closely associated with

Answer 38

-collagen XVII -fibronectin

Question 39

Collagen XVII

Answer 39

core protein of a proteoglycan

Question 40

fibronectin

Answer 40

a fibrous protein important in the adhesion of connective-tissue cells to matrix)

Question 41

Fibrous proteins

Answer 41

glycoproteins with short oligosaccharide side chains)

Question 42

Laminin-1 structure

Answer 42

a large, flexible protein composed of three very long polypeptide chains (α, β, and γ) held together by disulfide bonds.

Question 43

True or false: heterotrimers can self-assemble through interactions with their tails

Answer 43

False: interactions with their heads

Question 44

What is a component of most laminin heterotrimers

Answer 44

Laminin γ-1 chain

Question 45

Structure of a laminin molecule

Answer 45

-3 polypeptide chains (alpha, beta, gamm) coiled around eachother -Integrin binding site -Perlecan binding site -Dystroglycan binding site -Nidogen binding site at bottom -Another integrin bind site on N terminal -self assembly sites

Question 46

Integrin binding site

Answer 46

membrane proteins present on cells, shows that molecule can interact with other cells through integrins

Question 47

Perlecan and dystroglycan bind site

Answer 47

can interact with other ECMs

Question 48

N terminal binding site

Answer 48

means that this molecule can be organized between 2 cells through interaction with integrins on both of them, while stil binding the ECM

Question 49

Self-assembly site

Answer 49

the laminin molecule can be bound to another laminin molecule while still being bound to other cells and ECM components- gives us nice sheath lining

Question 50

What gives the basal lamina tensile strength

Answer 50

Type IV collagen

Question 51

What is the second essential component of the mature basal lamina

Answer 51

Type IV collagen

Question 52

Why does type IV collagen exist in several isoforms

Answer 52

it consists of three separately synthesized long protein chains. They assemble via terminal domains into flexible, felt-like networks that give basal lamina tensile strength.

Question 53

The kidney glomerulus

Answer 53

has an unusually thick basal lamina that acts as a molecular filter preventing the passage of macromolecules from the blood into the urine.

Question 54

Mutations in type IV collagen genes

Answer 54

result in an irregularly thickened and dysfunctional glomerulus filter (hereditary kidney disorder - Alport Syndrome).

Question 55

The basal lamina can act as a ______ for the movement of cells

Answer 55

Selective barrier

Question 56

The basal lamina prevents what from contacting epithelial cells

Answer 56

prevents fibroblasts in the underlying connective tissue from contacting epithelial cells

Question 57

The basal lamina does not prevent what from passing through, and how

Answer 57

macrophages or lymphocytes, use specialized proteases to cut a hole for transit

Question 58

Basal lamina plays a role in what after injury and how

Answer 58

Tissue regeneration, basal lamina survives injury and creates a scaffhold along which regenerating cells can migrate

Question 59

What is responsible for many forms of muscular dytrophy

Answer 59

Defects in components of the basal lamina or in proteins that tether muscle cells to the basal lamina at the synapse

Question 60

Basal lamina also gives information to cells about

Answer 60

Gives lots of information to cells in repect to where to traffic receptors to, where to extend axons, etc

Question 61

True or False. Unlike conventional ion channels, individual gap junction channels remain open continuously once they are formed.

Answer 61

False

Question 62

True or False. A sheet of basal lamina underlies all epithelia.

Answer 62

True

Question 63

Certain bacteria secrete enzymes that can digest protein or carbohydrate components of the basal lamina. Why do you suppose they do so?

Answer 63

Tissue invasion

Question 64

When you wake up in the morning and turn on the light, is dopamine release increased or decreased? How does dopamine alter the neuronal activity in the retina?

Answer 64

Closes gap junction

Question 65

What does cell metabolism do