Cell Bio Review - Stem Cells, Apoptosis

aerlands's version from 2015-12-07 01:49

Stem Cell Review

Question Answer
A blastomere from an 8 cell embryo is said to be __________ Totipotent
Cells from the inner cell mass are _________.Pluripotent
Embryonic stem cells are usually derived from:the nuclei of inner mass cells
If you were to stain a blastocyst (but still preimplantation stage) embryo for Oct4, where would you expect to find it?in the nuclei of inner mass cells (Oct4 is a TF)
What is the cell or cell types that embryonic pluripotent stem cells CANNOT differentiate into?Pluripotent cells can differentiate into all but trophectoderm (forms extraembryonic tissue)
For a patient with Parkinson’s, why would embryonic stem cells derived from a cloned embryo (generated with the patient’s DNA) be more advantageous than embryonic stem cells from an existing line of embryonic stem cells?There is less likelihood of immune rejection or graft vs. host disease.
Describe how alteration of the cleavage plane during stem cell division could alter the cell fates of the daughter cells.Controlling rotation and alignment of the mitotic spindle results in daughter cells of different sizes and different fates. This involves connections between cell adhesion proteins and molecular motors. Spindle orientation is responsible for division symmetry. If the cell divides in a way that one daughter cell is closer to the niche, the other will be pushed out to replenish tissue. If both stay in the niche neither will differentiate.
You discover a candidate master gene that induces any cell type to become a pluripotent stem cell. What kinds of experiments could you perform to prove that your induced stem cells are really pluripotent?One way to do this would be to inject the cells into host such as a mouse. If the cells generate a teratoma with all 3 germ layers (endoderm, ectoderm, and mesoderm) then the cells are pluripotent. A second way to prove this would be to tag the cells with GFP and implant them into a pseudopregnant mouse. The resulting offspring should have GFP cells everywhere because the cells would be able to contribute to all 3 germ layers if pluripotent.
What factors are used to create induced pluripotent stem cells (iPSCs)?Factors such as Oct4, Sox2, Klf4, amd Myc are introduced using a viral vector to activate endogenous genes.
How might pluripotent stem cells represent a better alternative to disease treatment than embryonic stem cells or stem cells derived from therapeutic cloning?Pluripotent stem cells are a more ethical alternative. They are developed using the patient's own cells without destroying embryos; also there is no risk of a virus reactivating stem cell genes which could be proto-oncogenes.

Apoptosis Review

Question Answer
How is apoptosis different from necrosis?Apoptosis is a neat and orderly process while necrosis is messy. Apoptosis is an orchestrated sequence of events resulting in cell shrinkage, loss of cell adhesion to neighboring cells, and blebbing. Necrosis is characterized by swelling of a cell and its organelles, membrane breakdown, leakage of contents, and inflammation. (Implosion vs explosion)
PI-3 kinase activity helps prevent apoptosis by:mediating the inactivation of Bad by AKT
What would you predict would happen if you were to inject cytochrome C into the cytoplasm of a cell?Cytochrome C activates APAF1 and caspase 9 so it would activate the assembly of the Apoptosome, resulting in activation of pro-caspase-9, then the caspase-9-complex, followed by executioner procaspases which would be cleaved into executioner caspases and carry out apoptosis.
Describe the roles of Bcl and Bax in either promoting or inhibiting apoptosis. Bax promotes apoptosis when it oligomerizes with Bak, forming the Mitcochondrial Apoptosis-induced Channel (MAC). The complex then inserts itself into the mitochindrial membrane. Bcl inhibits apoptosis by inhibiting Bax/Bak, and also binds and sequesters APAF1 (APAF1 is involved with stimulatng the assembly of the apoptosome).
Apoptosis is similar to many signal transduction pathways, which include a receptor, intermediates/adaptors and effectors. Using the Tumor Necrosis Factor (TNF) receptor as a model, describe how an extracellular signal sets in motion the apoptotic cascade.


Caspases fall into two classes, initiator and effector caspases. Describe some of the downstream targets of effector caspases.


Question Answer
How does cytochrome c activate apoptosis?Cytochrome C, which is an electron transporter which normally resides in the mitochondria, is released into the cytoplasm after Bax/Bak activation. Cyto-C then activates APAF1 and procaspase-9, which in turn form the activated initiator caspase-9 complex, also known as the Apoptosome. The complex then activates executioner pro-caspases, which are cleaved into executioner caspase which carries out apoptosis.
Using your knowledge of the DNA damage checkpoint and apoptosis, Draw out the chain of events leading from DNA damage can lead to effector caspase activation and apoptosis. Make sure you include all the relevant intermediates in the two cascades.

Matching terms

Match the hallmark of programmed cell death with the effector protein responsible


Question Answer
Membrane blebbingActivated Rho-kinase
Nuclear fragmentationCaspase-activated DNAase (CAD)
Mitochondrial Breakdown MAC
Cytosolic protein, activates Caspase 9APAF


Question Answer
Initiator caspasesCaspase 8 and Caspase 9
Effector caspasesactivated by initiator caspases, responsible for cleaving most apoptotic substrates
Bcl2apoptosis inhibitor; resides in mitochondrial membrane, inhibits Bax/Bak, sequesters and binds APAF1
APAF1activates caspase 9, forming activated caspase-9 complex (aka the Apoptosome)
p53upregulates Bax/Bak
Bax: combines with Bak to form MAC
Question Answer
Bakcombines with Bax to form pro-apoptotic pore in mitochondrial membrane
PI3-Kinaseinhibited by MDM2
MACformed by Bax/Bak, releases cytochrome C and other pro-apoptotic proteins
Caspase 8recruited and activated by cell-surface recptors
Caspase 9activated by APAF-1
Fas/CD95speicalized surface receptrs: Death Receptors (DRs)
CAD(Caspase-activated DNAse) - responsible for DNA fragmentation