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MCB 3010 > Passgeways from cell to cell and Basal Lamina > Flashcards

Passgeways from cell to cell and Basal Lamina Flashcards

1
Q

What blocks passageways through gaps between cells

A

Tight junctions

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2
Q

What to tight junctions prevent

A

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

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3
Q

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

A

Gap junctions (animals)
Plasmodesmata (plants)

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4
Q

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

A

small molecules, macromolecules

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5
Q

Gap junctions couple cells both ______ and ________

A

electrically, metabolically

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6
Q

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

A

connexins, innexins

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7
Q

Differences and similarities between connexins and innexins

A

Unrelated in sequence but similar in shape and function

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8
Q

Do connexins or innexins predominate in vertebrates

A

Connexins

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9
Q

Summarized explanation of channels formed by gap-junction proteins

A

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.

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10
Q

A gap-junction connexon is made up of

A

six transmembrane connexin subunits

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11
Q

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

A

A continuous aqueous channel that connects the two cell interiors

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12
Q

How is a hemichannel formed

A

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

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13
Q

What happens in regard to ions when hemichannels form

A

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

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14
Q

What conformation are hemichannels generally kept in

A

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

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15
Q

Why can gap junctions in different tissues have different properties

A

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

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16
Q

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

A

False, they can.

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17
Q

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

A

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

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18
Q

Can cells regulate the permeability of their gap junctions

A

Yes

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19
Q

Gap-junction channels close when

A

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

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20
Q

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

A

Isolates the cell, prevents its neighbors from harm

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21
Q

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

A

Dopamine

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22
Q

What does dopamine do in retina

A

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

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23
Q

What does the reduction in retina gap-junction permeability do

A

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

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24
Q

The matrix is composed of various _____ and _____

A

proteins and polysaccharides

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25
Q

Proteins and polysaccharides (that make up matrix) are secreted

A

locally

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26
Q

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

A

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

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27
Q

Basal lamina is also referred to as the

A

basement membrane

28
Q

The basal lamina surrounds what cells (3)

A

Muscle cells, fat cells and Schwann cells

29
Q

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

A

True

30
Q

Basal lamina differences in muscle vs epithelium cells

A

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

31
Q

Functions of the basal lamina

A

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

32
Q

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

A

Basal lamina

33
Q

Defects in certain basal lamina proteins cause the epidermis to

A

Become detached from the dermis

34
Q

What is the primary component of the basal lamina

A

Laminin

35
Q

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

A

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

36
Q

2 main classes of basal lamina

A

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

37
Q

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

A

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

38
Q

Basal lamina is closely associated with

A

-collagen XVII
-fibronectin

39
Q

Collagen XVII

A

core protein of a proteoglycan

40
Q

fibronectin

A

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

41
Q

Fibrous proteins

A

glycoproteins with short oligosaccharide side chains)

42
Q

Laminin-1 structure

A

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

43
Q

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

A

False: interactions with their heads

44
Q

What is a component of most laminin heterotrimers

A

Laminin γ-1 chain

45
Q

Structure of a laminin molecule

A

-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

46
Q

Integrin binding site

A

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

47
Q

Perlecan and dystroglycan bind site

A

can interact with other ECMs

48
Q

N terminal binding site

A

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

49
Q

Self-assembly site

A

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

50
Q

What gives the basal lamina tensile strength

A

Type IV collagen

51
Q

What is the second essential component of the mature basal lamina

A

Type IV collagen

52
Q

Why does type IV collagen exist in several isoforms

A

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.

53
Q

The kidney glomerulus

A

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

54
Q

Mutations in type IV collagen genes

A

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

55
Q

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

A

Selective barrier

56
Q

The basal lamina prevents what from contacting epithelial cells

A

prevents fibroblasts in the underlying connective tissue from contacting epithelial cells

57
Q

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

A

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

58
Q

Basal lamina plays a role in what after injury and how

A

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

59
Q

What is responsible for many forms of muscular dytrophy

A

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

60
Q

Basal lamina also gives information to cells about

A

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

61
Q

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

A

False

62
Q

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

A

True

63
Q

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

A

Tissue invasion

64
Q

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?

A

Closes gap junction

65
Q

What does cell metabolism do

A

MCB 3010 (20 decks)

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