Bio344-Exam#3 (Q's & A's)

Question 1

What does the protein cohesin do?

Answer 1

It keeps identical chromosomes attached to each other

Question 2

What are the components of a proteoglycan?

Answer 2

protein, a tetrasacharide linker and glycosaminoglycans

Question 3

Which cyclin becomes abundant in a cell when the cell moves from the G2 phase into mitosis?

Answer 3

M cyclin

Question 4

Which factor below would directly impact filament growth rates?

Answer 4

subunit concentration

Question 5

What does the protein Myc do?

Answer 5

It is a DNA binding protein that increases transcription of the cyclin D gene which codes for the G1 cyclin.

Question 6

How does Ca2+ cause muscle contraction?

Answer 6

it binds troponin which shifts tropomyosin on the actin filaments

Question 7

What happens to microtubules when they lose their GTP cap?

Answer 7

they will likely shrink

Question 8

What is a function of the basal lamina?

Answer 8

filters toxins from blood in the formation of urine

Question 9

What is a function of hemidesmosomes?

Answer 9

anchor cells to the extracellular matrix

Question 10

What would happen in a cell if p27 proteins are degraded?

Answer 10

A p27 protein can bind to a cyclin Cdk complex thus in the absence of p27 many CdK would remain active.

Question 11

What is the structure of collagen?

Answer 11

Three alpha-helices wrapped around each other

Question 12

What does the E2F protein do?

Answer 12

It is a DNA binding protein that initiates S-phase gene transcription

Question 13

What extracellular signal causes a cell to divide?

Answer 13

mitogens

Question 14

What kind of proteins are gap junctions made out of?

Answer 14

connexins

Question 15

What happens if the DNA of a dividing cell is damaged?

Answer 15

The enzyme p53 is activated

Question 16

What could activate the enzyme p53?

Answer 16

DNA damage

Question 17

What enzyme is responsible for moving a cell between the different phases of the cell cycle?

Answer 17

cyclin dependent kinase

Question 18

What protein is present in desmosomes?

Answer 18

cadherin

Question 19

What protein reduces M-CdK levels during the M phase?

Answer 19

APC

Question 20

How can an active cyclin dependent kinase complex be inactivated?

Answer 20

through inhibitory phosphorylation

Question 21

Why does proteolysis of the extracellular matrix impact the severity of cancer?

Answer 21

degradation of the extracellular matrix allows cancerous cells to spread through the body

Question 22

What is a function of tight junctions?

Answer 22

prevent movement of small molecules between cells

Question 23

The cytoskeleton in animal cells…

Answer 23

is dynamic and changes all the time

Question 24

Which cells excrete large amounts of extracellular components?

Answer 24

fibroblasts

Question 25

Where in most cells would you expect to find actin bundles?

Answer 25

right below the plasma membrane

Question 26

Which protein below, if hyperactive, could lead to cancer?

Answer 26

Myc

Question 27

What are the three parts of the myosin protein?

Answer 27

motor head, hinge region and tail

Question 28

What protein is present in the nucleation complex of microtubules?

Answer 28

gamma-tubulin

Question 29

What filament is mostly responsible for mechanical strength?

Answer 29

intermediate filaments

Question 30

What is the motif present in the amino acid chains that make up collagen?

Answer 30

glycine amino acid X amino acid Y

Question 31

What do survival factors do?

Answer 31

they inhibit apoptosis

Question 32

Which of the following is true of gap junctions?

Answer 32

they may be opened or closed

Question 33

How does a high level of Ca2+ effect cell to cell binding?

Answer 33

it causes the cadherins to become rigid and promotes homolytic binding between cells

Question 34

How do your muscles move?

Answer 34

myofibrils are contracted when myosin pulls on actin filaments

Question 35

which protein is common in the extracellular matrix?

Answer 35

collagen

Question 36

In which phase does cytokinesis occur?

Answer 36

the M phase

Question 37

Which group of proteins are motor proteins that interact with actin filaments?

Answer 37

myosin

Question 38

What enzymes initiate the apoptosis cascade?

Answer 38

caspases

Question 39

What type of polysaccharide is present in the extracellular matrix?

Answer 39

glycosaminoglycans

Question 40

What are the 4 phases in the cell division cycle?

Answer 40

G1, S, G2, and M

Question 41

What is apoptosis?

Answer 41

programmed cell death

Question 42

What protein below binds to the basal lamina?

Answer 42

integrin

Question 43

What does gelsolin do?

Answer 43

it breaks actin filaments

Question 44

What filament is involved with movement of vesicles around the cell?

Answer 44

microtubules

Question 45

What do actin subunits need to bind to be incorporated into a filament?

Answer 45

ATP

Question 46

What happens to actin filaments immediately after a blood platelet is activated?

Answer 46

Actin filaments are first severed producing many actin filament fragments

Question 47

Which of the following often occurs during apoptosis?

Answer 47

cytochrome C is released from the mitochondria.

Question 48

Where is the microtubule organizing center in the cell?

Answer 48

centrosome

Question 49

Which of the following proteins could decrease the rate of filament growth inside a cell?

Answer 49

stathmin

Question 50

What does the Rb protein do?

Answer 50

It functions as a brake of the cell cycle by binding the E2F protein.