Lecture 5

Question 1

different junctions starting from the topmost type

Answer 1

• zonula occludens
• zonula adherens
• macula adherens (desmosomes)
• gap junction
• hemidesmosomes

Question 2

what makes up the zonula Occludens?

Answer 2

membrane proteins: Occludins and claudin, whihc comme together to make homo-dimers that hold the cells together
cytoplasmic proteins: ZO-1, actin

Question 3

what is another name for zonula occludens?

Answer 3

tight junctions

Question 4

what makes up Zonula Adherens?

Answer 4

membrane proteins: Cadherins
cytoplasmic: a-actinin, vinculin, actin

Question 5

what is the intercellular space between cells in zonula adherens?

Answer 5

15 nm

Question 6

what is another name for macula adherens?

Answer 6

desmosomes

Question 7

what makes up macula adherens?

Answer 7

intercellular space contains TM proteins Desmocollin and Desmoglein.
Plaque contains desmoplakins I and II, Plakoglobin, and desmocalmin
Intermediate filaments: keratin (no polarity)

Question 8

what is the intercellular space between cells attached via macula adherens?

Answer 8

25 nm

Question 9

what makes up hemidesmosomes?

Answer 9

plaque: BP 200
TM proteins: integrins (a6b4) and BP 180
intermediate filaments: tonofilaments

Question 10

what makes up gap junctions?

Answer 10

6 connexins, which make a connexon, attaches to another connexon from the other cell to make a channel that is 1.5 nm in diameter

Question 11

intercellular space between gap junction?

Answer 11

2 nm

Question 12

when talking about stem cells, what does steady state mean?

Answer 12

of newly originated cells by the stem cell are equal to the # of dead cells on the surface of the epithelium

Question 13

what is turnover time?

Answer 13

the time required to change the whole population of epithelial cells

Question 14

what is the turnover time of skin

Answer 14

30 days

Question 15

what is radioautography and how does it work?

Answer 15

• provides a means to study the turnover of epithelial cells and of other cell types
• works by adding radiated Thymidine (H3-T), then using photographic development which will allow us to see a black dot where the DNA is radioactive

Question 16

what is the purpose of cell division?

Answer 16

During embryogenesis and postnatal development, for growth.
During adulthood, to maintain tissue.

Question 17

what are the 3 ways cells/tissues behave in adulthood?

Answer 17

static (e.g. neurons and skeletal muscle)
Expanding (e.g. liver)
Renewing (e.g. epidermis)

Question 18

how many chromosomes (and pairs) do humans have?

Answer 18

23 pairs, so 46 total

Question 19

what are the phases of the cell cycle? how long is each?

Answer 19

G1: presynthesis of DNA; 25 hours – 2n
S: synthesis of DNA; 8 hours
G2: post DNA duplication; 3 hours – 4n
Mitosis: 2.5 hours – 2n

Question 20

what are the stages of mitosis?

Answer 20

1. preprophase: intranuclear condensation of chromosomes
2. prophase: visualization of chromosomes and mitotic spindle
3. metaphase: chromosomes in equatorial plane and loss of nuclear envelope/nucleolus
4. early anaphase: longitudinal splitting of chromosomes
5. late anaphase: migration of chromosomes to the poles
6. telophase: nuclear restitution, nuclear envelop and nucleolus formation