Chapter 20

Question 1

describe epithelial tissue (3)

Answer 1

also called epithelium =multicellular sheets in which epithelial cells are joined
-cells have different shapes and can be single layer or multi-layered
-epithelia covers external surfaces of body and line cavities/organs

Question 2

describe epithelium cell polarity

Answer 2

-epithelial cells are polarized : apical and basal(basolateral) sides

apical = upper & free /could have cilia etc
baso= lower and attached to basal lamina

Question 3

epithelial sheets rest on a ___ ____ which consists of ……

Answer 3

epithelial sheets rest on a basal lamina which consists of collagen and laminin atop connective tissue

Question 4

what are the 3 types of intercellular junctions

Answer 4

anchoring junctions: (strongest/ distribute stress)
-desmosomes
-adherens
-hemidesmosomes

tight junctions: (waterproofing)

gap junctions: (movement of solutes)

Question 5

what do intercellular junctions do

Answer 5

hold cells together

Question 6

what are cadherins

Answer 6

link two separate cells together and are tethered via linker proteins that attach to actin filaments inside the cell
-form a belt-like structure around epithelial cells

Question 7

what are desmosomes

Answer 7

-bind epithelial cells in sheets / allow keratin of adjoining cells to be connected
-great tensile strength

Question 8

what are hemidesmosomes

Answer 8

-bind epithelial cells to basal lamina via integrins

Question 9

what are integrins

Answer 9

adhere the cells to basal lamina / joined to the keratin filaments via linker proteins

Question 10

describe the orders of each anchoring junction

Answer 10

desmosomes
= keratin - linker (cytoplasmic plaque) - cadherins

hemidesmosomes
= keratin - linker (cytoplasmic plaque) - integrins

adherens
= actin - linker - cadherins

Question 11

describe tight junctions

Answer 11

=waterproofing / provide a tight seal

-help polarize cells
-bound by occludin/claudin protein complexes

Question 12

how can movement of proteins be restricted in the cell

Answer 12

cell junctions particularly tight junctions

Question 13

describe gap junctions

Answer 13

-function in communication between neighboring cells
-allow for inorganic ions and small water soluble molecules to pass from one cell to another
~they pass between pores formed by connexon complexes
-open/close in response to extracellular signals

Question 14

describe cancer

Answer 14

develops do to an accumulation of mutations that blow past checkpoints

~cancer cells are genetically unstable
-one cell requires an mutation that gives it an advantage over its neighbors / the daughter cells of the best adapted cells then continue to divide becoming the dominant clone in the developing tumor
*Ras

Question 15

what are the two types of cancer mutations

Answer 15

-oncogenes
-tumor suppressor genes

Question 16

what is metastases

Answer 16

-secondary tumors

Question 17

tumors that metastasize are called ___ ____

Answer 17

malignant tumors

Question 18

describe oncogenes

Answer 18

when there is a mutation in a proto-oncogene its called an oncogene
=gain of functions (dominant)

-mutation in one allele is sufficient
-increases risk of cancer as gas pedal is permanently on

Question 19

describe tumor suppressor genes and give examples

Answer 19

turn into inactive tumor suppressor genes when mutated
=loss of function (recessive)

-both alleles mutated (turned off)
-brakes don’t work
-increases levels of cyclin-Cdks when dont want them

ex. Rb, p53, APC

Question 20

describe case study progeria

Answer 20

-mutation into S phase that doesn’t get repaired on chr. 1 / large amounts of progerin
-effects lamins
-C–>T but gets missed
-loss of 150bp / 50 AAs from cyptic 5’ splice site

Question 21

what’s a cryptic splice site

Answer 21

adds an extra splice site

Question 22

what does progeria affect

Answer 22

affects breakdown and reformation of nuclear envelope