REINHART 1

Question 1

what are the layers of the small intestine tissue?

Answer 1

1. epithelium
   a. epithelial cells
   b. basement membrane
2. connective tissue
   a. fibroblasts
3. smooth muscle
   a. circular fibers
   b. longitudinal fibers
4. connective tissue
   basement membrane
5. epithelium

Question 2

what is the characteristic of epithelial cells?

Answer 2

all attached to each other
present on many other external surfacesw

Question 3

what are characteristic of basement membranes?

Answer 3

always present
thin matrix sheet

Question 4

how are fibroblasts arranged?

Answer 4

do not touch each other
more dispersed

Question 5

what do smooth muscle cells do?

Answer 5

muscle contractions

Question 6

what are the two types of occluding junctions?

Answer 6

1. tight junctions (vertebrates only)
2. septate junctions (mainly invertebrates)

Question 7

what are the relative concentrations of glucose in the lumen, into the cell and the blood?

Answer 7

low in the lumen, high in the cell, low in the blood

Question 8

how does glucose go from the lumen of the gut to the inside of the cell?

Answer 8

through sodium driven glucose symports
membrane proteins
cells need to have a glucose uptake against the gradient
but there is a high Na content in the cut and low Na content in the cell
when Na diffuses into the cell glucose will follow through with the sodium through the symports

Question 9

how does the glucose go from the cell into the blood?

Answer 9

facilitated diffusion, goes through passive glucose carrier protein

Question 10

how does electron microscopy work?

Answer 10

there is a cathode (electron donor) and an anode (acceleration)
100,000V of power is provided to accelerate the electrons
this gives a wavelength of 0.004nm
there is an ultraslow pressure vacuum
the specimen is cut ultra thin (50-100nm) so that electrons can pass through
osmium tetroxide is used for contrast to produce an image

Question 11

what is another way that the path of something through an organism can be followed?

Answer 11

tracer molecule, such as lanthanum (atomic number 57)

Question 12

what is another way to visualise cells?

Answer 12

freeze fracture electron micrograph
freeze and then fracture the plasma membrane

Question 13

what are the two proteins that make up tight junction proteins?

Answer 13

Claudin and occludin

Question 14

what is the mass of Claudins?

Answer 14

20-27kDa

Question 15

how many homologous members of Claudins?

Answer 15

24

Question 16

what are some mutations that can happen to claudins and the consequences?

Answer 16

claudin 16 mutations cause a loss of Mg2+ in the urine

Question 17

what is the mass of occludins?

Answer 17

65kDa

Question 18

how many forms of occludins are there?

Answer 18

2 isoforms, created by alternative splicing

Question 19

how is the localisation of occludins determined?

Answer 19

through phosphorylation

Question 20

which proteins give anchorage to cytoskeleton?

Answer 20

ZO proteins
zonula occludens
attach to actin filaments

Question 21

how are occludins and claudins organised in the bilayer?

Answer 21

run through the PM 4 times
both the C and N termini are inside the cell
claudins interact with claudins
occludins interact with occludins
makes for very tight connections

Question 22

what is the average mass of an amino acid?

Answer 22

110Da
between 100-120

Question 23

which are the cytoskeletal fibers involved in cell junctions and what are they made of?

Answer 23

actin filaments: actin
intermediate filaments: keratin, vimentin, desmin

Question 24

what are the cytoskeletal fibers not involved in cell junctions and what are they made of?

Answer 24

microtubules, made of tubulin

Question 25

what are two examples of tight junction associated hereditary diseases?

Answer 25

gene: Cldn1
neonatal ichthyosis and sclerosing cholangitis (itchy and flaky skin)
gene: Cldn14
non syndromic deafness

Question 26

what are the different anchoring junctions?

Answer 26

1. actin filament attachment sites
   a. cell cell junctions (adherens junctions)
   b. cell matrix junctions (focal adhesions)
2. intermediate filament attachment sites
   a. cell cell junctions (desmosomes)
   b. cell matrix junctions (hemidesmosomes)

Question 27

what do anchoring junctions give?

Answer 27

stability

Question 28

what are cadherins?

Answer 28

adherens junctions
desmosomes

Question 29

what are integrins?

Answer 29

focal adhesions
hemidesmosomes

Question 30

how are cells attached to each other through anchoring?

Answer 30

cytoskeletal filament bound to adaptor protein
adaptor protein bound to cadherins
cadherins bind to each other in the intercellular space and provide cell-cell anchoring

Question 31

how are cells attached to the extracellular matrix?

Answer 31

cytoskeletal filaments bound to adaptors
adaptors bound to integrins
integrins connected to the matrix
transmembrane adhesion proteins

Question 32

how is the cell attached to actin filaments?

Answer 32

Cadherin goes through plasma membrane
on cytosolic side attached to the p120 catenin and beta catenin (smaller) and alpha catenin
alpha catenin is longer, can interact with vinculin
vinculin interacts with actin filaments

Question 33

what do cadherin dimers depend on?

Answer 33

calcium