CTCS Quiz 2

Question 0

How long does it take between successive mitoses?

Answer 0

~24 hours, but this can be variable.

Question 1

How long does mitosis las for a cell in culture?

Answer 1

1 hour.

Question 2

In which phase dose repair of the genome occur?

Answer 2

S phase.

Question 3

Early Prophase

Answer 3

Chromatin make chromosomes, spindle fibers begin to form.

Question 4

Late Prophase

Answer 4

Nuclear envelope goes away, chromosomes attach to spindles.

Question 5

Metaphase

Answer 5

Chromosomes align at metaphase plate, held in tension by the opposing spindle fibers.

Question 6

Anaphase

Answer 6

Sister chromatids are pulled apart, spindle poles start to move apart from each other.

Question 7

Telophase

Answer 7

Chromatids arrive at poles, nuclear envelopes reform around decondensing chromsomes, cleavage furrow begins begins and causes cytokinesis.

Question 8

Are the key mechanisms governing M phase conserved?

Answer 8

Yes. They are conserved in all species (yeast to man).

Question 9

What can cause a cell cycle to stop in M phase?

Answer 9

unattached chromosomes or incorrect spindle assembly.

Question 10

What can cause the cell cycle to arrest in G1?

Answer 10

Damaged DNA.

Question 11

What can cause the cell cycle to arrest in G1 or G2?

Answer 11

DNA damage or unreplicated DNA.

Question 12

What regulates the main events of the cell cycle?

Answer 12

Cdk-Cyclin complexes.

Question 13

How does the cell make sure not to go backwards?

Answer 13

It destroys certain proteins after they are used,- ie destruction of M-cyclin

Question 14

What does MPF stand for and what makes it?

Answer 14

M-phase Promoting Factor.

It is made by: 1) a Cdk catalytic subunit (Cyclin Dependent Kinase), 2) M-cyclin (or cyclin B sometimes)

Question 15

What is M-Cdk?

Answer 15

Mitosis- Cyclin-Dependent Kinase

Question 16

How quickly are MTs renewed during mitosis?

Answer 16

All are renewed with a half life of 15 secs.

Question 17

How many directions can an individual motor protein travel on a spindle?

Answer 17

One. Some MPs can go towards the plus end, some towards minus end.

Question 18

What actions can motor proteins have on spindles?

Answer 18

Slide, push, pull

Question 19

What happens with M-Cdk is destroyed?

Answer 19

Mitosis ends.

Question 20

What are some key structural features of cytokinesis?

Answer 20

1. Actin and myosin filaments make contractile ring.
2. Nuclear envelopes and membrane-bound organelles reformed.
3. Golgi and other organelles send membrane to site of fission to help heal.

Question 21

What are the three major filaments found in a cell?

Answer 21

Intermediate Filaments, MTs, and Actin Filaments

Question 22

Which filaments are polar?

Answer 22

MTs and Actin

Question 23

Which two filaments are important for cell motility?

Answer 23

Actin and MTs

Question 24

What makes up MTs, Microfilaments and IFs?

Answer 24

MTs: Tubulin MFs: Actin IFs: Nestin, Vimentin, Keratins, Desmins, etc. (not important to memorize)

Question 25

How is MT made?

Answer 25

1. Heterodimers with alpha and beta tubulin | 2. GTP must be bound to both alpha and beta subunits

Question 26

What is the inner and outter diameter of MTs? How wide is an alpha or beta unit?

Answer 26

Inner: 14 nm Outter: 25 nm Alpha/Beta: 4-5 nm

Question 27

How is Actin polymerized?

Answer 27

G actin makes dimers, then trimers, then they elongate at the barbed end (+ end). It now becomes known as F actin.

Question 28

What is required for polymerization of actin?

Answer 28

1. G-acting has to be above critical concentration. | 2. ATP-Mg bound to actin

Question 29

Are IFs polarized?

Answer 29

No

Question 30

Where are IFs found in the cell?

Answer 30

Everywhere.

Question 31

What property does IF have?

Answer 31

Rope-like properties, high tensile strength.

Question 32

How are actin filaments regulated?

Answer 32

G and F-Actin binding proteins.

Question 33

How do G-actin binding proteins work?

Answer 33

They bind to the monomers and either add them to the actin, or they prevent them from going to the actin. These different proteins compete for the actin substrates.

Question 34

What are Actin Related Proteins (ARP)?

Answer 34

ARP2/3 induces nucleation at branched junction at 70 degrees animals.

Question 35

What do formins do?

Answer 35

They elongate actin filaments.

Question 36

What do Rho proteins do?

Answer 36

They determine the structure of the actins. Other proteins do this, too, but they determine whether the actin makes stress fibers, lamellipodia, filopodia, etc.

Question 37

Is MT growth symmetric?

Answer 37

No, it is assymetric.

Question 38

What are the 2 mechanisms that regulate MT dynamics?

Answer 38

1. Inherent properties of tubulin assembly. | 2. MT associated proteins.

Question 39

What does a GTP cap do to MTs?

Answer 39

It can prevent depolymerization. But if hydrolysis catches up to the tip, as soon as the tip is mostly GDP, then rapid depolymerization occurs.

Question 40

What is one function of a microtubule associated protein (MAP)?

Answer 40

The can act as spacers in neuronal cells.

Question 41

What can happen to MTs when they are stabilized?

Answer 41

They can be modified. They are always modified with the plus end in the direction of the moving cell.

Question 42

Can protein cap MTs to stabilize them?

Answer 42

Yes.

Question 43

Are stabilized MTs affected by drugs?

Answer 43

No.

Question 44

What fills most of the extracellular space in connective tissue?

Answer 44

Glycosaminoglycans (GAGs). They are unbranched polysaccharide chains, repeating units, and one sugar is always an amino sugar.

Question 45

What is one of the simplest GAGs?

Answer 45

Hyaluronic acid. It can be made up of 25,000 repeating units.

Question 46

What is a proteoglycan?

Answer 46

An ECM protein, heavily glycosylated, and one chain must be a GAG.

Question 47

How does the Na/K pump work?

Answer 47

- 3 Na out, 2 K in | - requires ATP

Question 48

What is one of the reasons why a high extracellular Na+ concentration is important?

Answer 48

Na+ is used to help bring other molecules back into the cell with cotransport (symport). It has to be flowing along its gradient in order to do this.

Question 49

How does Na+ help to regulate acidity inside the cell?

Answer 49

Antiport. For every Na+ that enters cell, one H+ leaves the cell.

Question 50

What is the difference between GAGs and Proteoglycans?

Answer 50

GAGs: occupies lots of space and make gels. Proteoglycans: composed of GAGs bonded to a core protein.