Cell Bio Exam 4

Cholera is caused by a bacterial toxin, and the disease symptoms include profuse diarrhea. How does the cholera toxin cause these symptoms?

changes the permeability of the tight junctions

during kinesin movement down a microtubule, what directly causes the trailing head to be thrust forward?

original leading head binding to ATP

Which of the following is true of individuals with spontaneous retinoblastoma?

tumors usually develop later in life

What is the principle CAM for tight junctions?

occludin

The ubiquitin ligase that promotes the destruction of a specific set of proteins, thereby promoting the separation of sister chromatids and the completion of M phase

APC/C

What is the function of Rb in the cell cycle?

Acts as an inhibitor of E2F

Kinesin 13 is active during which stages of the cell cycle?

All stages

How are S phase cyclin/cdk complexes activated?

By release and degradation of the cdk

What molecule promotes entry into the cell cycle?

EGF

MCM helicases are needed to unwind DNA for replication. When are they loaded onto DNA?

End of M phase

During which stages of the cell cycle is the MTOC NOT the spindle pole?

G0, G1

Mitogens are added to the medium of cultured human cells that are synchronized in mitosis. The mitogen is washed away after theses cells have passed the restriction point in the cell cycle. These cell will progress through the cell cycle, then arrest in which phase?

G0,G1

The phase of the eukaryotic cell cycle between the end of cytokinesis and the start of DNA synthesis

G1 phase

Endocytosis and exocytosis of vesicles occurs during which stages of the ell cycle?

G1, S, G2

People often take chondroitin when they have a joint injury. What component of the ECM is a chondroitin?

GAG

The integrins are found on leukocytes. What protein does the integrin bind to on endothelial cells during extravasation?

Ig-CAM

What set of molecules is involved in tight leukocyte attachment to endothelial cells, just prior to extravasation?

Integrin activation on the leukocyte and binding to ICAM on the endothelial cell

What is the role of CapZ in actin filaments?

It binds to the positive ends of actin filaments and prevents new monomers from being added

How can one of the cholera toxins work to cause disease?

It promotes the efflux of chloride

How can the second cholera toxin work to cause disease?

It reduces the number of tight junctions

What is the function of MAP2?

Its a protein that helps decrease the number of catastrophes

What is the function of the Arp2/3 complex?

Performs a nucleating function to form branched networks of actin

How does the nuclear envelope dissociate during mitosis?

Phosphorylation causes nuclear pore proteins to degrade

What is encoded by a tumor suppressor gene?

RB

Rho proteins are important in signaling changes in the formation of the actin cytoskeleton. This ultimately leads to cell movement, such as aiding in wound healing. How does activation of Rac trigger cell movement?

Rac activates Arp2/3 complex, which generates the leading edge

What nuclear transport protein is also involved in chromatid capture

Ran

what is the different between type I and type IV collagen?

Type IV collagen forms a 2D fiber network and is found in the basal lamina

Rho proteins are important in signaling changes in the formation of the actin cytoskeleton. This ultimately leads to cell movement, such as aiding in wound healing. How does activation of Rho trigger cell movement?

Rho activates formins, which generates stress fiber formation

How do formins become activated?

Rho-GTP binds to the Rho binding domain, wich leads to a conformation change in formin

during what phase of the cell cycle is cyclin E active?

S phase

Cohesins are attached to the chromatids during which stages of the cell cycle?

S, G2, prophase, prometaphase, metaphase

What is the function of ATM in the cell cycle checkpoints?

Senses DNA damage and holds the cell cycle in G1 until the damage is repaired

When APC/C is complexed with cdh1, what happens?

The M phase cyclins are degraded

What process ensures that the same region of a chromosome is not duplicated twice during DNA replication?

The MCM helicases can only be loaded during times of low cdk activity

If a dominant active cdc42 protein was made, such that I was permanently locked into the GTP bound state, and this protein was transfected into cells, what would occur?

The cells would forma leading edge of the cell, but be unable to migrate in a single direction

P53 is involved in the DNA damage checkpoint. What is its function?

Transcribes genes that repair the DNA damage

What is the function of sic?

acts as an inhibitor of the S cyclins

in what stage of the cell cycle do cohesins break down

anaphase

what is the class of microtubules responsible for orienting the axis of cell division

astral microtubules

Where would you find type IV collagen?

basal lamina

a tumor that is self limiting in growth and non invasive

benign tumor

Release of calcium from the sarcoplasmic reticulum acts to contract muscle cells by directly

binding to troponin

which end of keratins is favored for polymerization or adding on subunits?

both are equally favored

Integrins are proteins that can change the motility and movement of cells. How are integrins regulated?

by expression

How are mitotic cyclin/cdk complexes activated?

by phosphorylation of the cdk

What is the CAM for adherins junctions?

cadherins

What molecule is needed for cadherin to bind to another cadherin?

calcium

a cancer arising from epithelial cells

carcinoma

Where are microtubules nucleated from?

centrosome

What is the principle structural component of the basal lamina that forms the mesh network?

collagen IV

What is the principle CAM for gap junctions?

connexina

What is the function of fibronectin in the ECM?

crosslinking

What is a major function of a GAG in the ECM?

cushioning

A member of the family of protein kinases that have to be complexed with a cyclin protein in order to act

cyclin dependent kinase (cdk)

What is the key step in allowing anaphase to proceed?

degradation of securin through APC/C

What is the direct function of the SCF?

degrades sic

Epithelial cells have what on their lateral surfaces?

desmosomes

What is the first set of cell-cell interactions that occurs that will ultimately lead to leukocyte attachment to endothelial cells, and subsequent extravasation?

endothelial expression of P selectin and binding of the leukocyte

In what types of cells would you find lamins

in all cells

What is the principle CAM for hemidesmosomes?

integrins

What is the function of a cdc in the cell cycle?

is a phosphatase

What is the function of E2F in the cell cycle

is a transcription factor

What molecule aids in the breakdown of microtubules

kinesin 13

What is the function of Tem1 in cell cycle checkpoints?

makes sure all chromosomes are properly segregated to opposite sides of the cell

A tumor or tumor cell that can invade surrounding tissue from other tumors at other sites in the body

malignant tumor

What component of the cytoskeleton is associated with tight junctions?

microfilaments

During what phase of the cell cycle is cylcin D expressed?

mid G1

What cell type would you most likely find desmins?

muscle cells

What motor moves cargo towards the positive end of the microtubule?

myosin

Dynein transports organelles to which end of the microtubule?

negative end

What end of the microtubule remains anchored to the MTOC?

negative end

What is the main function of cyclin B?

phosphorylates nucleoporins

what is a main function of cyclin D, after it is complexed to its appropriate cdk?

phosphorylates the retinoblastoma protein

What is the class of microtubules responsible for pushing the chromosomes apart and keeping them separated from one another during prometaphase?

polar microtubules

Which end of the microtubule is favored for polymerization or adding on subunits

positive end

The microtubules capture the chromosome pairs during what phase of mitosis?

prometaphase

in what stage of the cell cycle does the nuclear envelope break down?

prometaphase

what are kinetochores

proteins that attach the microtubules to chromatids

What protein directly releases the sister chromatids from each other during the metaphase to anaphase transition?

separase