August 15 2019 Stem cells Cell Death Flashcards
What are totipotent stem cells?
Stem cell that has the potential of a single cell to develop into a total organism. Ex: a fertilized egg and the 4-cell stage embryo
What are Pluripotent stem cells?
Stem cells that have the capacity to give rise to all cell types in the body, but not to the supporting structures, such as the placenta, amnion, and chorion
What are Multipotent stem cells?
Stem cells that have the capacity to give rise to a small number of different cell types.
What are Unipotent stem cells?
Stem cells that have the capacity to give rise to only one cell type.
What type of cells are at the base of the crypt of the lumen of the gut and aid in the continual renewal in the lining of the intestine?
Dividing Crypt Base Columnar (CBC) Stem Cells
What controls levels of beta-catenin in cells?
The Wnt Signaling Pathway
What happens to beta-catenin in the absence of Wnt?
In the absence of Wnt, Beta-catenin protein is made and targeted for ubiquitin-mediated degradation in the proteasome by the APC E3 ubiquitin ligase.
What happens to beta-catenin when Wnt binds to the frizzled receptor?
Beta-catenin ubiquitylation is inhibited. Beta-catenin translocates to the nucleus and interacts with TCF and other stimulatory factors and stimulates the transcription of target genes
Name and describe the nature of the two pathways that can cause apoptosis and what they have in common.
Intrinsic (response to internal stress), and extrinsic (activation of death receptors); they can trigger apoptosis by activating the enzymatic caspase cascade.
Describe the steps of intrinsic pathway of apoptosis AKA mitochondrial integrity pathway
DNA damage leads to Bax pro-apoptotic signal to be inserted into mitochondrial membrane. Cytochrome c is release from mitochondria into the cytoplasm, activating Apaf-1. Apaf-1 converts pro-caspase 9 to active caspase 9 which serves as initiator caspase, stimulating the caspase proteolytic cascade, resulting in degradation of cellular proteins.
How does Bcl-2 family member Bid regulate apoptosis?
For survival, Bcl-2 binds Bid, and prevents the association of Bid with Bax (pro-death). For apoptosis, Bid binds to Bax and a channel opens in mitochondria, releasing cytochrome c.
Describe the extrinsic apoptotic pathway.
Signal from outside the cell triggers interaction between Fas receptor and FasL on another cell. receptor trimers are formed and bring cytoplasmic death domains together, initiating adaptor molecule binding (TRADD and FADD). Death-inducing signaling complex (DISC) is formed. Caspase 8 is activated and activates downstream caspases, committing cell to death by apoptosis.
Which apoptotic pathway does FasL on cytotoxic T lymphocytes initiate, and how?
extrinsic pathway. FasL on CTL binds to FasR on target cell, activating caspases 8 and 10. CTL also expresses Granzyme B, which is released into target cell, and activates caspase 3. Bid is cleaved to tBid, mitochondrial membrane permeability increases, and cytochrome c is released.
How do apoptotic cell membranes differ from those of viable cells, and how does this help phagocytic cells recognize apoptotic cells?
Apoptotic cells loses its cell membrane asymmetry, and phosphathidylserine changes positions from the inner to the outer leaflet. Phagocytic cells have receptors for PS.
In intrinsic apoptosis; what are the anti-apoptotic regulators?
Bcl-2 and Bcl-xL
In intrinsic apoptosis; when would a channel open in the mitochondria?
When Bid binds to Bax, a channel in the mitochondria willopen, and cytochrome c will be released from it.
