Question 1

What are the three main types of cell death pathways?

Accepted Answer

Cells can die through apoptosis, autophagy, or necrosis. Apoptosis is programmed cell death characterized by membrane blebbing and nuclear fragmentation. Autophagy, also regulated, involves formation of large vacuoles enclosing cellular components. Necrosis is unplanned cell death resulting in cell lysis and loss of nuclei.

Question 2

How do caspases function in apoptosis?

Accepted Answer

Caspases are protein-degrading enzymes that serve as key regulators in the apoptosis pathway. These enzymes are activated during programmed cell death and can be detected using caspase activity assays, where fluorescent substrates reveal their activation. The ced-3 gene encodes caspase, linking genetic control to apoptotic mechanisms.

Question 3

What is the trypan blue assay used for in cell death research?

Accepted Answer

The trypan blue assay is a screening tool that identifies cell death by exploiting membrane differences. The stain cannot enter live cells with selective membranes but easily enters dead cells with ruptured membranes. However, this assay identifies cell death generally without pinpointing the specific pathway involved.

Question 4

How can researchers distinguish between different cell death pathways?

Accepted Answer

Researchers use annexin V and propidium iodide stains paired with flow cytometry analysis to distinguish death pathways. Annexin V binds to phosphatidylserine residues in membranes, while propidium iodide enters damaged membranes to associate with DNA. This combination allows scientists to separate cells undergoing different death mechanisms.

Question 5

What role does autophagy play in cell survival and death?

Accepted Answer

Autophagy is a regulated process where cellular components are engulfed and broken down by autophagosomes, which fuse with lysosomes for further destruction. This process plays a dual role in cells, either facilitating survival during nutrient stress or inducing death when dysregulated. Christian de Duve's discovery revealed this fundamental cellular mechanism.

Question 6

How did research in C. elegans worms advance understanding of apoptosis?

Accepted Answer

Studies of C. elegans development revealed that specific cells undergo apoptosis at consistent times across different worms, suggesting genetic control. Researchers identified ced genes responsible for this process, with mutations preventing programmed cell death during development. This work established that apoptosis is genetically regulated rather than random.

Question 7

What can live cell imaging reveal about cell death mechanisms?

Accepted Answer

Live cell imaging allows scientists to observe cell death in real time and identify autophagic, necrotic, or apoptotic cells based on unique morphological features. This all-encompassing technique provides visual confirmation of death pathways without requiring cell fixation. It complements biochemical assays by showing dynamic cellular changes during death.

מבוא למוות בתא - חידון הערכה