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MCB 3010 > Quiz 2 review lecture flashcards > Flashcards

Quiz 2 review lecture flashcards

1
Q

What junction prevents extraceullular molecules from leaking from one side of an epithelium to the other

A

Tight junctions

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2
Q

What junctions allows cells to interact with their neighbours

A

Gap junction

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3
Q

Hemichannel

A

When a connexon from one cell does not line up with one from another cell, opens up to extracellular space - essentially a pore that can allow ions in and out of cells

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4
Q

The extracellular space is occupied by an intricate network of macromolecules constituting the

A

Extracellular matrix

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5
Q

The matrix is composed of various ______ and ____________

A

Proteins and polysaccharides

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6
Q

In our 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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7
Q

True or false: The basal lamina is the underpinning of all epithelia

A

True

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8
Q

2 Tissues of basal lamina is found

A

muscle and epithelium

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9
Q

Muscle tissue basal lamina

A

Basal lamina wraps around cells and follows muscle path

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10
Q

Epithelium basal lamina

A

more polar in organization – there is a sheath of villi on the top and the basal surface is attached to the basal lamina which is right above connective tissue

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11
Q

Basal lamina cell functions

A

-determines cell polarity
-influences cell metabolism (controls directional flow of nutrients)
-organizes the proteins in adjacent PM
-promote cell suvival, proliferation, differentiation

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12
Q

Mechanical role of basal lamina (skin)

A

The epithelial outer layer (epidermis) depends on the strength of the basal lamina to keep it attached to the underlying connective tissue (dermis)

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13
Q

2 essential components of the basal lamina

A

Laminins and type IV collagen

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14
Q

Laminins role basal lamina

A

Primary organizer of the sheet structure, the basal lamina consist primarily of laminin molecules

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15
Q

Type IV collagen role basal lamina

A

Gives basal lamina tensile strength.

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16
Q

How does the basal lamina act like a filter

A

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

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17
Q

Matrix in connective tissue and basal lamina: Two main classes of macromolecules they are cosntructed from

A

1) glycosaminoglycan (GAG) polysaccharide chains usually covalently linked to proteins in the form of proteoglycans
2) fibrous proteins such as collagen

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18
Q

Polysaccharide role ECM

A

Resist compressive forces on the matrix while permitting rapid diffusion of nutrients, metabolites and hormones between the blood and tissue cells

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19
Q

Collagen fibers role ECM

A

Strengthen and organize matrix, while other fibrous proteins such as elastin (rubber-like) give it resilience

20
Q

The ability to cut through the matrix is crucial in two ways:

A

1) it enables cells to divide while embedded in the matrix
2) it enables them to travel through it

21
Q

Why is the ability to cut through matrix required by white blood cells

A

To cross the basal lamina of blood vessels into tissues in response to an injury

22
Q

Cells degrade matrix components through extracellular ________

A

proteases

23
Q

Two general classes many proteases belong to:

A

1) matrix metalloproteases, which depend on bound Ca2+ and Zn2+
2) serine protease, which have a highly reactive serine in their active site

24
Q

Three basic control mechanisms of proteases

A

Local activation: Activate inactive proteases, plasminogens become active when cleaved by plasminogen activators, active plasmin helps break up blood clots

Confinement by cell-surface receptors: Cell-surface receptors bind to proteases confining the enzyme to where it is needed

Secretion of inhibitors: Secretes protease inhibitors

25
Q

Fibronectin role

A

Helps cells attach to matrix

26
Q

Mutant mice that cant secrete fibronectin: what happens?

A

Die early because their endothelial cells are unable to form proper blood vessels

27
Q

RGD binds to cells through an

A

RGD motif that binds integrins

28
Q

Outside-in signalling

A

Signal comes from outside and transduced into the cells
- the stimulus binds to that RGD domain in fibronectin, causes a structural change which now the talin binding domain becomes revealed
-This allows for the integrin that is bound to fibronectin in the EMC to be linked to the cytoskeleton of the cell
-Talin is the connection that links integrin to the cytoskeleton

29
Q

Inside-out activation

A

Example: Ligand binds to RTK – dimerization – transautophosphorylation, formation of docking sites to initiate the signalling cascade
-PIP2 is phosphorylated to pip3
(It is possible that PIP2 OR PIP3 can change the structure of talin) so that it opens talin binding sites to bind to integrin causing the structure change in integrin so that it is activated on the extracellular side
-Both pip2 and pip3 activation is proposed
-Bidirectional

30
Q

Cell-adherence junctions (4)

A

1) Anchoring junctions (desosomes)
- anchor the cells to each other and then anchor the cells to the ECM
2) Occluding junctions (tight junctions)
-ensure nothing leaks through the epithelial layer, found generally along apical side
3) Channel-forming junctions (Gap junctions)
-usually closer to basal side, allow transfer of small molecules between cells
4) Signal- relaying junctions (Notch Delta)
- membrane bound ligand on one cell that interacts with membrane bound receptor on another cell, transmits signal to both

31
Q

Cadherins mediate

A

adherens junctions

32
Q

Adherens junctions link

A

actin cytoskeleton between 2 cells

33
Q

Linking the cytoskeleton to the ECM is always done at the ____ side of an epithelial cell: actin through ________ and IF through __________

A

basal: integrin signalling, hemidesosomes

34
Q

Development of a neural tube what part develops the peripheral nervous system

A

Neural crest on top

35
Q

Ectoderm to neural tube

A

-Start with ectoderm that has high expression of E-Cadherin
-This layer infolds which develops the neural tube
-This causes a shift to a high expression of N-cadherin and down regulate E-cadherin
-The junctions of the fold have a different expression – up regulation of cadherin 6B causing these folds to actually fuse
-What you get is the neural tube closing with separated cells above and cells that can migrate, differentiate and change their expression to cadherin 7

36
Q

B-catenin involvement with cadherins

A

B-catenin involved with cell junction AND WNT SIGNALLING: Wnt activates genes involved with cadherins involving cadherins themselves

37
Q

Collagens are extremely rich in …
A. alanine and valine.
B. glycine and proline.
C. lysine and arginine.
D. serine and threonine.
E. tyrosine and phenylalanine.

A

B

38
Q

What is the main function of fibroblast cells?
A. Connect the cell to the ECM
B. Secreting components of the ECM
C. Help disperse the mechanical stress
D. Connect the basal lamina to the ECM
E. Activate mast cells

A

B

39
Q

What are the two essential components of the basal lamina?
A. Type IV collagen and Laminin γ-1
B. Type I Collagen and Fibronectin
C. Elastin and Type IV Collagen
D. Laminin and Perlecan
E. Elastin and Laminin

A

A

40
Q

2 types of short segments elastin molecule is made up of

A

1) Hydrophobic segments - responsible for elastic properties
2) Alanine and lysine rich alpha-helical segments

41
Q

Similarities and diferences between collagen and elastin

A

SAME:
-both rich in proline and glycine
DIFFERENT:
-only collagen is glycosylated
-elastin contains hydroxyproline NOT hydroxylysine

42
Q

Laminin and collagen molecule

A

LAMININ-1:
-Large, flexible protein composed of 3 peptide chains (alpha, beta, gamma)
COLLAGEN:
-Long, stiff triple stranded helix , 3 alpha chains wound around eachother
-rich in glycine (EVERY 3rd A.A)

43
Q

Integrins are

A

Transmembrane heterodimers that can link to cytoskeleton

44
Q

Cadheins only found in

A

Animals

45
Q

Particular type of IF attached to desosome in each cell type

A

keratin filaments in most epithelial cells and desmin filaments in heart muscle cells

MCB 3010 (20 decks)

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