Molecular Cell Biology - Test Bank

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Questions and Answers

Which of the following triggers apoptosis?

  • NGF
  • TNFα
  • Fas ligand
  • Fas ligand and TNFα (correct)

What role does cytochrome c play in apoptosis?

  • Promotes cell division
  • Binds to and activates Apaf-1 (correct)
  • Releases harmful toxins
  • Activates ATP production

Mitochondrial permeabilization results in increased ATP synthesis.

False (B)

What is released from mitochondria to trigger apoptosis?

<p>cytochrome c</p> Signup and view all the answers

Apoptosis can be induced by the release of ________ into the cytosol, which activates Apaf-1.

<p>cytochrome c</p> Signup and view all the answers

Which event has likely NOT occurred if a cell exhibits condensed chromatin and a shrunken cytoplasm?

<p>Activation of caspases (A)</p> Signup and view all the answers

Match the protein with its function in apoptosis:

<p>XIAP = Inhibits initiator and effector caspases SMAC/DIABLO = Promotes caspase activation Bax = Forms channels in the mitochondrial membrane Bad = Promotes apoptosis by inhibiting Bcl-2</p> Signup and view all the answers

Which mitochondrial protein binds to Apaf-1 to activate the caspases?

<p>Cytochrome c (A)</p> Signup and view all the answers

What role does the niche play in stem cell division?

<p>It orients the mitotic spindle. (C)</p> Signup and view all the answers

Tight junctions in epithelial cells recruit apical PAR complexes.

<p>True (A)</p> Signup and view all the answers

What is the function of PAR proteins during asymmetric cell division?

<p>They facilitate the orientation of the spindle.</p> Signup and view all the answers

In C. elegans, the gene ______ encodes a caspase.

<p>ced-3</p> Signup and view all the answers

Which of the following best describes necrosis?

<p>None of the above. (D)</p> Signup and view all the answers

Match the apoptotic proteins with their descriptions:

<p>CED-3 = Caspase involved in apoptosis CED-4 = Activator of caspases CED-9 = Homologous to human Bcl-2 EGL-1 = Displaces CED-9 from mitochondria</p> Signup and view all the answers

What happens to the daughter cells after asymmetric cell division?

<p>They inherit different fate determinants. (A)</p> Signup and view all the answers

CED-9 is a pro-apoptotic protein in C. elegans.

<p>False (B)</p> Signup and view all the answers

Which statement is FALSE regarding the stem cells in the epithelial lining of the small intestine?

<p>Lgr5 encodes an R-spondin receptor. (C)</p> Signup and view all the answers

Which of the following is part of the cell lineage that gives rise to T cells?

<p>Pluripotent hematopoietic stem cell (C)</p> Signup and view all the answers

Floral meristems only give rise to leaves.

<p>False (B)</p> Signup and view all the answers

What proteins do cap cells in the Drosophila ovary secrete that aid in maintaining germ-line stem cells?

<p>Dpp and Gbb</p> Signup and view all the answers

When a germ-line stem cell divides, the daughter cell maintaining the _______ association becomes a stem cell.

<p>E-cadherin</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Apoptosis = Programmed cell death Mitochondria = Powerhouse of the cell, involved in energy production Tight junctions = Barrier that controls passage of molecules between cells Stem cell niche = Microenvironment regulating stem cell behavior</p> Signup and view all the answers

What is the primary role of mitochondria in the process of apoptosis?

<p>Release cytochrome c into the cytoplasm. (A)</p> Signup and view all the answers

Homotypic E-cadherin interactions are essential for maintaining the stem cell niche in Drosophila.

<p>True (A)</p> Signup and view all the answers

Flashcards

Apoptosis triggers

Fas ligand, TNFα, or a combination of both can initiate the apoptosis process.

Mitochondrial role in apoptosis

Mitochondria release cytochrome c into the cytosol, which activates caspases initiating apoptosis.

Cytochrome c target in apoptosis

Cytochrome c binds to Apaf-1 in the cytosol, triggering a cascade of caspase activation.

Mitochondrial permeabilization effect

Permeabilization (creating holes) in the outer mitochondrial membrane triggers cytochrome c release, a crucial step in apoptosis.

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Apoptosis stages (missing event)

If apoptosis is triggered extrinsically, activation of caspases is a later step. Other events like receptor activation and recruitment of proteins occur first.

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XIAP protein function

XIAP proteins prevent caspases from initiating cell death.

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Mitochondrial protein in cytosol

Cytochrome c is the mitochondrial protein that binds to Apaf-1 in the cytosol.

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Trigger of cytochrome c release

Bax homodimers produce channels allowing ion influx into the mitochondria resulting in cytochrome c release. This is a key mechanism that can be impacted by various compounds.

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Asymmetric Cell Division

Cell division resulting in two daughter cells with different fates.

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Stem Cell Polarization

Stem cell response to cue for localization of fate determinants to one region, affecting daughter cell fate.

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Stem Cell Niche

A microenvironment that guides stem cell division, causing asymmetry in daughter cell fates.

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Epithelial Cell Tight Junctions

Structures that recruit complexes, including PAR, Scribble, and Crumbs.

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PAR Proteins

Proteins unevenly distributed in cells during asymmetric division.

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Necrosis

Cell death due to tissue damage without programmed sequence.

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Caspase (C.elegans)

Apoptotic enzyme encoded by the ced-3 gene in C. elegans, crucial for programmed cell death.

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CED-9 (C.elegans)

Protein homologous to human Bcl-2 protein, affecting apoptosis, a key part of cell death pathway.

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Intestinal stem cell marker

Lgr5 is a gene that encodes a receptor for R-spondin, a protein involved in Wnt signaling pathway, and is expressed by intestinal stem cells.

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Intestinal stem cell location

Intestinal stem cells reside in specialized pits called crypts located in the lining of the small intestine.

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Wnt signaling impact on Lgr5

Wnt signaling pathway induces the expression of the Lgr5 gene.

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T cell lineage origin

T cells originate from pluripotent hematopoietic stem cells.

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Floral meristem fate

Floral meristems produce both petals and stamens.

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Germline stem cell niche role

The niche in the Drosophila ovary provides signals that maintain germline stem cells in an undifferentiated state.

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Drosophila niche signals

Cap cells in the Drosophila ovary niche secrete Dpp, Gbb, and Hh signals that maintain germline stem cell identity.

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Cre recombinase in lineage tracing

Cre recombinase is used to specifically mark and follow the lineage of Lgr5-expressing intestinal stem cells.

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Study Notes

Molecular Cell Biology - Test Bank

  • Cell Birth, Lineage, and Death: Mammals follow a specific chronological order in development: zygote, four-cell stage, compacted morula, blastocyst.
  • Gamete Fusion (Fertilization): Mouse sperm must penetrate cumulus cells and the zona pellucida (ZP) layer. ZP3 glycoprotein binding on the sperm triggers the acrosomal reaction, releasing enzymes to degrade the ZP. This allows sperm-egg membrane interaction. Calcium release in the egg triggers cortical granule exocytosis, preventing polyspermy (multiple sperm entry).
  • Somatic Cell Nuclear Transfer (Cloning): Involves transferring the nucleus of a differentiated cell into an enucleated egg. This technique can efficiently be used in cloning mice.
  • Differentiation: The first differentiation event occurs when the trophoectoderm separates from the inner cell mass in the mouse embryo. These pluripotent stem cells are found in the inner cell mass.
  • Stem Cells: Daughter cells generated through asymmetric cell division can have different sizes, shapes, and protein compositions. Genes specifically expressed in pluripotent embryonic stem cells, such as Nanog, Sox2, and Oct4, are key indicators. Retroviral vectors expressing KLF4, c-MYC, and SOX2 proteins can reprogram differentiated cells into pluripotent stem cells.
  • Dolly the Sheep: Cloning Dolly involved somatic cell nuclear transfer.
  • Yamanaka's Studies: Researchers successfully reprogrammed differentiated cells back to stem cells through retroviral infection with transcription factors.

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