Cell biology VII Flashcards
Is the nucleolus membrane-bound?
No
Now many nucleoli are present in a typical cell?
1-2
What are the three components of the nucleolus?
1) Nucleolar-organizer DNA2) Pars fibrosa3) Pars granulosa
What is the function of nucleolar-organizer DNA?
Contains base sequence that codes for transcription of rRNA
What is the function of the pars fibrosa?
Newly transcribed rRNA just beginning to become complexed with proteins
What is the function of the pars granulosa?
Maturing subunits of ribosomes
What is nucleostemin?
p53 binding protein found in undifferentiated cells
What happens to the levels of nucleostemin as the cell becomes more differentiated?
Decreases
During what phase of the cell cycle does replication of centrioles begin?
G1
During what phase of the cell cycle is centriole replication complete?
G2
What events take place during prophase?
1) Chromatids are condensed2) Tetrads form3) Centromere forms4) Kinteochore forms5) Cytoplasmic microtubules are disassembled and reorganized into mitotic spindle6) Centriolar pairs migrate to opposite ends
During what phase of the cell cycle are chromatids condensed?
Prophase
During what phase of the cell cycle do tetrads form?
Prophase
During what phase of the cell cycle does the centromere form?
Prophase
During what phase of the cell cycle does the kinetochore form?
Prophase
During what phase of the cell cycle do microtubules disassemble and reorganize into mitotic spindle?
Prophase
During what phase of the cell cycle do centriolar pairs migrate to opposite ends of the cell?
Prophase
What is the starting point for prometaphase?
Disappearance of nuclear envelope
What events take place during prometaphase?
1) Nuclear envelope dissolves2) Attachment of microtubules to kinetochores3) Chromatids organize at equator of cell4) Nucleoli disappear
During what phase of the cell cycle are microtubules attaching to the kinetochore?
Prometaphase
During what phase of the cell cycle are chromatids organizing at the equator of the cell?
Prometaphase
During what phase of the cell cycle does the nucleolus disappear?
Prometaphase
What drug will arrest development at metaphase?
Colchicine
At what phase of the cell cycle does colchicine cause arrested development?
Metaphase
What events take place during anaphase?
Chromatids separate and are referred to as chromosomes
Telomerase is found in what cell types?
Germinal cells and stem cells
What happens when phosphatidylserine is translocated to the extracellular lipid monolayer?
Cell is marked for death
What are the characteristics of extrinsic pathway for caspase activation?
1) Fas ligand and Fas receptor (death receptor)2) Adaptor protein3) Inactive caspase 8 —-> active caspase 8
What are the characteristics of intrinsic pathway for caspase activation?
1) Cell injury causes release of cytochrome c2) Cytochrome c adaptor protein (Apaf-1) complex forms3) Inactive caspase 9 —-> activated caspase 9
What effect does estrogen have on osteoblasts?
Anti-apoptotic
What is the normal role of Bad?
Pro-apoptotic
When phosphorylated, is Bad active or inactive?
Inactive
What happens to Bad levels when estrogen is depleted?
Bad is inactivated
