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Bio 331 Final Exam > Cell Junctions > Flashcards

Cell Junctions Flashcards

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Biology 101 flashcards
1
Q

What determines the function of a protiens

A

It’s properties and interactions in junctions

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2
Q

What are the three membranes in the epithelium

A

Basal

Apical

Lateral

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3
Q

What is the apical

Basal

Lateral

Basal lateral

A

Top of cell facing lumen

Basal bottom (attached to ECM)

Side

Bottom and side

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4
Q

What special about the membranes of a polarized cell

A

It has a different apical membrane than its basal membrane

It has shape and functional asymmetry

It gives directionality

Key for migration,development and organization

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5
Q

What is a way to see the structure of cell junctions in a cell

How does it work

A

Electron microscopy

It uses electrons instead of light

Gives high resultion of the structures

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6
Q

What is special about electron microscopy

A

The samples are imaged in a vacuum meaning live cells can’t be imaged

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7
Q

What are the three junctions that make up the junctional complex

A

Tight (zonula occluden)

Adherens

Desmosome (macula adherens)

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8
Q

What are tight junctions

A

Junctions that tightly hold together neighbouring epithelial cells

At the apical membrane (top of the epithelial cells)

They stop solutes from distributing between each cell

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9
Q

What two functions do tight junction control

A

The gate function

The fence function

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10
Q

What is the gate function

What is it also called

A

It’s the function between cells plasma membranes

Where it controls the passage of molecules between cell plasma membranes

The para cellular pathway

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11
Q

What molecules does the gate function control

A

Ions

Protiens

The blood brain barrier (where ions/water can’t pass but immune system cells can)

Water

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12
Q

What is a tight junction protien that can be mutated and what is the result

A

Claudin 1

If mutated the cells aren’t tightly close enough so water molecules escape out of the cells

This leads to dehydration

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13
Q

What is the fence function of tight junctions

A

Occurs in one cell not between cells

But it needs two cells to operate

controls the diffusion of integral membrane protiens between the apical and the basal lateral membranes of the cell

Prevents diffusion and helps create polarity

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14
Q

What does a fence funtion to a tight junctions need in order to actually work

A

Needs to connect to the actin cytoskeleton and microtubules

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15
Q

In general what can tight junctions interact with

A

Actin and microtubules

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16
Q

What effect does polarity in tight junctions have on the process of wound healing

A

The tight junctions are broken due to the paper cut

Since the tight junctions are gone, the apical membrane protiens can move to the basal lateral membrane and vise versa

This cause a loss of polarity in the cell, and a ligand receptor interaction happens which trigger healing

17
Q

What are the adherins junctions

A

They connect the external environment around the cell to the actin cyctoskeletion on they inside of the cell

The allow for signals from the external environment to be transmitted to the cytoplasm and nucleus of the cell

18
Q

What do adherins junctions form around the cell

A

They form a belt called the zonula adheren which surround the cells apical surface

19
Q

What are adherins junctions generally made of and what do they depend on

A

Made of E cadherin

Cadherins are calcium dependent (need calcium to function)

20
Q

What are desmosomes

A

They also have cadherins (ca dependent) and are protien rich

the cadherins interact with these protiens to make cytoplasmic plaques on the inside surface of the cells plasma membranes

Then the two cells are anchored together by intermediate filaments (not actin)

21
Q

What do desmosomes help with

A

They give strength to a sheet of cells

22
Q

What are keratin intermediate filaments

A

They are in epithelial cells and give strength to the cell and tissues

The do this by making a heterodimer made of two diff keratins

These heterodimers make long dense cables

23
Q

What happens if there is a mutation in keratin genes

What causes the change In keratin gene expression and heterodimers

A

Skin fragility

Specializations (differentiation)

24
Q

Where are the most highly specialized cells in a epithelial cell

What about least

A

At the top (apical end) they lose their nuclei so the cant divide any more

Least is at the bottom which have the most capacity for proliferation and differentiation

25
Q

Which keratin intermediate filament markers are in the basal cell

What about the suprabasal (higher)

What are they each called

A

5 and 14

1 and 10

They are obligate pairs (one basic one acidic)

26
Q

What do the most specialized cells in epithelial cells help with

A

The keep the hydration level of the body and protect it from the external environment

27
Q

What are gap junctions

Where are they

A

They help in cell cell communication NOT STRENGTH

On the lateral side

they form intercellular channels (between cells) to transmit small soluble signaling molecules through the membranes

28
Q

How small are the soluble signalling molecules the are sent through gal junctions

A

Less than 1000 daltons

29
Q

What are gap junctions made of

A

6 same Connexin proteins from each cell makea transmembrane channel

This channel has a central pore called a connexon

Two connexons from each individual cells make a gap junction

30
Q

What do gap junctions open to

A

They’re basically pipelines that pass through each cells plasma membrane and open into each cells cytoplasm

31
Q

What is a gap junction plaque

A

It’s formed when A bunch of connexons a clustered together in a higher concentration in the cell

32
Q

What interactions invoked the cells inner surface

A

Hemidesmosome

And focal adhesions

33
Q

What are hemidesmosoms

Where are they

A

They’re similar in structure to desmosomes but have different function

The help interaction of the cell with extracellular materials while the cell is stationary

They are on the basement and basal membrane of the cell

34
Q

What is the structure of hemidesmosomes

A

The have a dense plaque of keratin filaments on the cytoplasmic side of the cell

And connect to collagen fibres in the extracellular matrix

These keratin filaments are linked to the ECM or basement membrane through the intergrin protien BP180

35
Q

What happens if BP180 is mutated

A

skin fragility

36
Q

What are focal adhesions

A

Also in basal membrane but involved in migration/ cell locotmotion

Use actin filaments

They disappear near the back of the cell. (Like how a foot lifts to move forward)

37
Q

Why is focal adhesion important

A

If helps the cells survive

If they can’t attach to the ecm and move along, it does cell death )apoptosis

38
Q

What is the process of a focal adhesion at work

A

An integrin of the cell attached to a protien in the ecm

This activated focal adhesion kinase (FAK) and SRC kinase

This then causes a chain reaction of signals being transmitted to the nucleus to tell the cell it should survive

Bio 331 Final Exam (17 decks)

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