Lecture 9

Question 1

What are the four connections/attachments that make the epithelia a barrier?

Answer 1

tight junction
adhering junction
desmosome
gap junction

Question 2

The epithelia is attached to a _________ _________. Describe this

Answer 2

basement membrane

this is part of the extracellular matrix that holds the cells in place

Question 3

Describe the cell membrane

Answer 3

It is a lipid bilayer

Question 4

What is the cell membrane permeable to?

Answer 4

non-polar, uncharged molecules such as O2, CO2 and steroid hormones

Question 5

What is the cell membrane impermeable to?

Answer 5

ions and large, charged molecules

Question 6

What are the three things that make up the lipid bilayer? What percentage of the membrane do each of these things make up?

Answer 6

• phospholipids: 75%
• cholesterol: 20%
• glycolipids: 5%

Question 7

Phospholipids have both a __________ region and a __________ region

Answer 7

hydrophilic

hydrophobic

Question 8

What two things make up the hydrophilic region of phospholipids?

Answer 8

an alcohol and a phosphate

Question 9

Where are the hydrophilic and hydrophobic regions of the phospholipids located?

Answer 9

The hydrophilic regions face the outside and inside of the cell and then the hydrophobic region faced each other, away from the aqueous inside and outside of the cell

Question 10

Is the hydrophilic head on cholesterol big or small? Why is this?

Answer 10

it is small so that it can be embedded in the lipid region

Question 11

There are ________ in the membrane which span the whole lipid bilayer. What are three examples?

Answer 11

proteins
GPI-anchored membrane protein
peripheral membrane protein
integral membrane protein

Question 12

Which protein does not span the membrane but holds onto it?

Answer 12

the peripheral membrane protein

Question 13

What is meant by the fluid mosaic of the lipid bilayer?

Answer 13

lipid molecules can move sideways in their own half of the bilayer

Question 14

Can proteins such as channels, receptors, transporters, ECM proteins move in the bilayer?

Answer 14

yes

they are embedded in the lipid bilayer but can still move

Question 15

What is the purpose of the fluid mosaic of the lipid bilayer?

it is __________ and __________ for changing _________ and _________ populations, cell _______, _________ and self-sealing

Answer 15

it is flexible and dynamic for changing protein and lipid populations, cell growth, secretion and self-sealing

Question 16

What is another name for the basement membrane?

Answer 16

basal lamina

Question 17

What joins the cells to the basement membrane?

Answer 17

hemidesmosomes

Question 18

Where are tight junctions located?

Answer 18

these are located close to the apical membrane of the cells

Question 19

Where do adhering junctions sit?

Answer 19

just below the tight junctions

Question 20

What is the basement membrane? What is it comprised of?

Answer 20

it is an extracellular matrix structure comprised of collagens, laminins, proteoglycans and fibronectins

Question 21

Where is the basement membrane secreted from?

Answer 21

from the epithelial cells themselves to help form the extra cellular matrix structure that they then sit on

Question 22

What is a condition that results from issues with the basement membrane?

Answer 22

epidermolysis bullosa

Question 23

What causes epidermolysis bullosa?

Answer 23

the collagen malfunctions so the anchoring of the basement membrane to the skin epithelia fails and blistering occurs

Question 24

Patients presenting with epidermolysis bullosa present with severe blistering BECAUSE collagen dysfunction prevents proper anchoring of basement membrane to the epithelial cell

Answer 24

A- Both true and related

Question 25

What are the three main functions of the tight junctions?

Answer 25

- act as a barrier - act as a gate - act as a fence

Question 26

Explain the tight junctions acting as a barrier (why is this needed?)

Answer 26

this limits the passage of ions and molecules between cells in the paracellular pathway

Question 27

Explain tight junctions acting as a gate (why is this needed?)

Answer 27

it can allow certain solutes to flow through the paracellular pathway

Question 28

Explain tight junctions acting as a fence (why is this needed?)

Answer 28

to prevent the movement of proteins between apical and basolateral domains

Question 29

Tight junctions are ________ structures around each epithelial cell - formed by strands of _______ proteins linked to bilayers of two cells pulling the bilayers very close together

Answer 29

continuous | claudin

Question 30

What three things make up a tight junction?

Answer 30

- claudin protein - occludin protein - JAMs

Question 31

What are claudin proteins, occludin protein, JAMs all connected to?

Answer 31

ZO proteins

Question 32

What are ZO protein connected to?

Answer 32

actin cytoskeleton

Question 33

What is the part of the tight junction that changes to make all 27 different kinds?

Answer 33

the claudin

Question 34

What does claudin 1 not allow through the tight junctions?

Answer 34

it does not allow transport of ions/water through the tight junctions

Question 35

What does claudin 2 allow through the tight junctions?

Answer 35

it allows the transport of many ions and water through the tight junctions

Question 36

Other claudins (not 1 or 2) control the passage of what?

Answer 36

Mg2+, Ca2+

Question 37

Describe the structure of the adherens junction

Answer 37

this is a belt structure beneath tight junction where two cells are close contact via cell-cell adhesion molecules (CAMs)

Question 38

What makes up the belt that forms part of the adherens junction?

Answer 38

actin filaments

Question 39

Formation of adherens junction initiates epithelia formation, true or false?

Answer 39

true

Question 40

What is an example of a CAM?

Answer 40

E - cadherin

Question 41

CAMs are held in place by what?

Answer 41

by anchor proteins which connect to actin cytoskeleton

Question 42

Why are CAMs important in cancer?

Answer 42

As the cancer progresses, the epithelia becomes mesenchymal and can cause metastasis due to the loss of adherence junctions so the epithelia become disorganised so the cells break off and go somewhere

Question 43

Describe the structure of desmosomes

Answer 43

There are desmosomal cadherins that hold cells together at single spots. There is an anchor point for intermediate filaments eg. keratin

Question 44

Describe the structure of a hemidesmosome

Answer 44

These connect the epithelial cells to the basement membrane and are directly involved with keratin intermediate filaments (these are embedded in a plaque and joined via the protein plectin to integrins)

Question 45

Describe gap junctions

Answer 45

These are tiny channels between cells made of connexin proteins

Question 46

Six connexins form a ________ that forms a _________

Answer 46

connexon | channel

Question 47

What do gap junctions allow the passage of?

Answer 47

ions and small molecules between cells

Question 48

What are the three main types of cytoskeleton?

Answer 48

- actin filaments - intermediate filaments - microtubules

Question 49

What is the purpose of actin filaments in the cytoskeleton?

Answer 49

determines cell shape, and drive the movement of cells

Question 50

What is the purpose of the intermediate filaments in the cytoskeleton?

Answer 50

to provide mechanical strength and resistance to shear stress

Question 51

What is the purpose of microtubules in the cytoskeleton? to position ___________, railroads for intracellular ________ transport, form a _________ spindle, motile components of _________

Answer 51

to position organelles, railroads for intracellular vesicle transport, form a mitotic spindle, motile components of cilia

Question 52

The cytoskeleton is ________ and can ________ to internal and external signals

Answer 52

dynamic | adapt

Question 53

____________ proteins regulate the _______/_________ and linking to other structures

Answer 53

accessory | assembly/disassembly

Question 54

Actin filaments form a ______ stranded _______ polymer of actin

Answer 54

2 | helical

Question 55

What are myosins? they are ________ proteins that bind to ________ filaments and use _______ for ________, and transport _______, vesicles and ________ along the _________ filaments

Answer 55

they are motor proteins that bind to actin filaments and use ATP for contraction, and transport proteins, vesicles and organelles along the actin filaments

Question 56

What are microtubules?

Answer 56

they are long straight hollow cylinders made from α and β tubulins

Question 57

Which is more rigid, actin filaments or microtubules?

Answer 57

microtubules

Question 58

What are microtubules needed for?

Answer 58

cell motility, cell division, vesicle movement

Question 59

What are two molecular motor that allow transport of vesicles and organelles around the cell using ATP?

Answer 59

kinesin and dynein

Question 60

``` What type of cell junction is a tight junction: occluding Anchoring strength communicating ```

Answer 60

occluding

Question 61

``` What type of cell junction are adherens: occluding Anchoring strength communicating ```

Answer 61

anchoring

Question 62

``` What type of cell junction are desmosomes: occluding Anchoring strength communicating ```

Answer 62

strength

Question 63

``` What type of cell junction are hemidesmosomes: occluding Anchoring strength communicating ```

Answer 63

strength

Question 64

``` What type of cell junction is a gap junction: occluding Anchoring strength communicating ```

Answer 64

communicating

Question 65

What are the transmembrane proteins for tight junctions?

Answer 65

claudin, occludin, JAM-1

Question 66

What are the transmembrane proteins for adherens?

Answer 66

E - cadherins

Question 67

What are the transmembrane proteins for desmosomes?

Answer 67

desmosomal cadherins

Question 68

What are the transmembrane proteins for gap junctions?

Answer 68

connexins

Question 69

What is the cytoskeletal attachment for adherens?

Answer 69

actin filaments

Question 70

What is the cytoskeletal attachment for desmosomes?

Answer 70

keratin filaments

Question 71

What is the cytoskeletal attachment for hemidesmosomes?

Answer 71

keratin filaments

Question 72

Desmosomes connect epithelial cells to the basement membrane BECAUSE the basement membrane consists of extracellular matrix proteins

Answer 72

False, true