Cell Signaling and Division Flashcards

Flashcards based on lecture notes covering cell signaling pathways, apoptosis, and cell division.

What can unrelated receptors do?

Signals from unrelated receptors can converge to activate a common effector.

What can identical signals do?

Identical signals can diverge to activate a variety of effectors.

What is cross-talk in cell signaling?

Signals can be passed back and forth between pathways from crosstalk.

What is convergence in cell signaling?

Signals from unrelated receptors lead to activation of a common effector.

What is the role of cAMP in crosstalk?

cAMP can block signals transmitted through the MAP kinase cascade.

To what do steroid hormones bind?

Steroid hormones bind to intracellular receptors to influence transcription directly.

What ligands bind to intracellular receptors?

Ligands that bind to intracellular receptors include small and lipophilic estrogen, testosterone, retinoic acid, and vitamin D.

What role does nitric oxide play as?

Nitric Oxide can act as an extracellular signal or second messenger.

What does cyclic GMP (cGMP) act as?

Cyclic GMP acts as a second messenger (like cAMP).

What is nitroglycerine converted to and what does it do?

Nitroglycerine, used to treat angina, is converted to NO and dilates blood vessels in the heart to increase blood flow.

How does NO stimulates cGMP?

NO stimulates guanylyl cyclase, making cGMP.

What does cGMP lead to?

cGMP leads to smooth muscle relaxation.

What is the role of Viagra?

Viagra is a specific inhibitor of phosphodiesterase 5 isoform that brakes down cGMP.

What cellular changes occur during apoptosis?

Cell shrinkage, loss of adhesion to other cells, dissection of chromatin, and engulfment by phagocytosis.

What are the proteolytic enzymes that activate apoptotic changes?

Caspases

Name two intrinsic signaling cascades that result in Apoptosis.

DNA damage, mitochondrial dysfunction, etc.

What happens during Apoptosis to Phosphatidylserine?

During apoptosis, a phospholipid “scramblase” moves phosphatidylserine to the outer leaflet of the plasma membrane, serving as an “eat me” signal to attract macrophages.

How does apoptotic cell death prevent inflammation?

Apoptotic cell death occurs without spilling cellular contents to prevent inflammation, compared to necroptosis.

What does intracellular stimuli such as DNA/mitochondrial damage cause during the Intrinsic Pathway of Apoptosis?

Leak protein cytochrome c

What does cytochrome c form when it leaks into the cytosol?

Once in the cytosol, cytochrome c forms part of a multiprotein complex called the apoptosome, that also includes several molecules of procaspase-9.

What is the death ligand that is detected by a TNF cell surface receptor?

Tumor Necrosis Factor (TNF)

What does RIPK3 activate?

MLKL (Mixed Lineage Kinase Domain-Like protein)

What protein oligomerizes and triggers that rupture of cellular membranes, releasing intracellular contents and leading to necrotic cell death?

MLKL (Mixed Lineage Kinase Domain-Like protein)

Mitosis vs. Meiosis

Mitosis leads to production of cells that are genetically identical to their parent, whereas meiosis leads to production of cells with half the genetic content of the parent.

What are cells that divide often?

Stem cells (blood, intestine, skin), spermatogonia, plant root, tumor cells

What are cells that divide when stimulated?

Liver, lymphocytes

What are cells that are unable to divide?

Highly differentiated cells: nerve cells, muscle cells, red blood cells

What is the quiescent stage?

G0: not come up to divide but are capable upon activated.

What happens when cells do not regulate cell division correctly?

Cancer: breakdown cell’s own ability of regulating its own division.

Name the distinct stages of the eukaryotic cell cycle

M phase and Interphase (G1, S, G2)

What is the Cell Cycle

Unidirectional

What does the cytoplasm contain?

Factors that regulate the progress of cell cycle.

What initiates entry into the M phase?

Maturation Promoting Factor (MPF)

What are essential in regulation of the cell cycle?

Protein kinases

What two subunits makeup MPF (Maturation Promoting Factor)?

A kinase and a regulatory subunit, cyclin.

What does increased concentration of cyclin do?

Activates the kinase

What controls cell cycle progression?

Cyclin dependent kinases (cdk’s)

Which kinases regulate checkpoints?

Cyclin/kinase complexes regulate two checkpoints (near the end of G1 (START) and near the end of G2)(G2– M transition).

What is one of the checkpoints located at (that determines whether they will complete the cell division and reenter G1 of the next cycle.)?

Middle of Mitosis

What does Cells with a mutant wee1 gene produce?

Cells with a mutant wee1 gene cannot maintain the Cdk in an inactive state and divide at an early stage in the cell cycle producing smaller cells, hence the name wee.

What cannot Cells with a mutant cdc25 gene do?

Cells with a mutant cdc25 gene cannot remove the inhibitory phosphate from the Cdk and cannot enter mitosis.

What degrades cyclins?

Controlled proteolysis via the ubiquitin-proteasome pathway degrade cyclins.

Cells may synthesize other proteins that do what?

Inhibit progression through the cell cycle.

Failure to clear checkpoints can arrest what?

The cell cycle

Which cellular functions are autonomously shut down when cells sense severe damage?

Apoptosis: programmed cell death

What is Mitosis?

A process of nuclear division in which two nuclei with identical genetic content are produced to maintain chromosome number.

The cell devotes virtually all of its energy to chromosome?

Segregation

What are the phases of Mitosis?

Prophase, prometaphase, metaphase, anaphase, and telophase.

What cellular functions are greatly minimized or stopped during mitosis?

Transcription, translation, movement, metabolism, response to environment