Exam #1: Cell Biology VII Flashcards
When is the nucleolus best viewed?
In a euchromatic cell
NO
- Nuclear Organizer
- Lightly stained
- Contains DNA that is used to transcribe mRNA that is used for the formation of ribosomal subunits (rRNA)
PF
- Pars Fibrosa
- Early packaging of ribosomal subunits
PG
- Pars Granulosa
- Maturing of ribosomal subunits
NAC
Nucleolus Associated Chromatin
Nucleostemin
- p53 binding protein
- Found in undifferentiated cells
- Decreases as cells become more differentiated
What is the relationship between nucleostemin & cancer?
- Nucleostemin binds p53
- Blocks DNA damage checkpoint
- Allows progression through the cell cycle unchecked
What are the steps of the cell cycle?
1) G1
2) S
3) G2
4) M
What is the S-phase checkpoint?
DNA Damage
What is the G2 checkpoint?
DNA Damage
G0
- Normal resting cell state
- Long-lived cells spend a long time in this phase
Centriole Duplication
- Starts in G1
- Continues in S
- Completed in G2 so there are two pairs of centrioles
What are the important drivers of the cell cycle?
Cyclins
When does the replication of chromosomes occur?
S-phase
In G1 how many chromosome are there?
23
In G2 how many chromosomes are there?
46 (referred to as chromatids)
What happens in mitosis?
Separation of homologous chromatids
What are the stages of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What is the functional outcome of mitosis?
- Transition from one nucleus to two nuclei
- Mitosis alone does not include cell division
- It is normal to have cells that are tetraploid
What is an example of a normal tetraploid cell?
Cardiac muscle cell
Prohpase
- Nuclear envelope intact
- Centrioles migrate to opposite sides of cell
- Chromosomes condensed
Prometaphase
- Initiated by phosphorylation of lamins & disassembly of nuclear envelope
What drugs inhibit mitosis, and how?
- Colchicine (Gout)
- Vincristine (Cancer)
- Vinblastine (Cancer)
Inhibit polymerization of microtubules
What drug promotes polymerization & inhibits depolymerization of microtubules?
Taxol
Metaphase
Chromatids aligned in the center of the cell
Anaphase
Sister chromatids pulled to opposite ends if the cell
What needs to occur for separation of the chromatids to occur?
- Cohesion complexes must be digested
- Initiated by APC
APC
- Anaphase promoting complex
- Activated Separase
Separase
- Enzyme that cleaves cohesion complexes
- Allows for separation of chromatids in anaphase
Telophase
- Chromatids at opposite sides of the cell
- Nuclear envelope reassembles
What types of filaments interact at the cleavage furrow for cytokinesis?
Actin & Myosin
Cytokinesis
Contraction of actin & myosin at the contractile ring causes a narrowing & pinching off of the single cell to make two cell
Cytochalasin B
Inhibits polymerization of actin microfilaments & thereby prevent cytokinesis
Telomeres
- Sequence of DNA on the end of the chromosome
- Some lost with each round of somatic cell division
- Germ-cells do not lose
Telomerase
Enzyme that maintains telomere length
What is the relationship between telomerase & cancer?
Cancer cells express telomerase & therefore can divide indefinitely
Necrosis
- Violent mechanism of cell death
- Cell fragments/ explodes & exposes antigenic material to immune system
- Causes an immune response/ inflammation
Apoptosis
- Programmed Cell Death
- Eliminates itself non-violently without activation of inflammatory response
What eliminates apoptotic bodies?
Phagocytosis
What side of the cell membrane is phosphatidylserine normally located on, and how is this related to apoptosis?
- Normally on the cytosolic monolayer
- Flipping to the extracellular monolayer marks the cell of apoptosis
Intrinsic Apoptosis Pathway
- Involved in cell injury
- Pro-apoptotic factors triggered that influence the mitochondria
- Cytochrome C released
Extrinsic Apoptosis Pathway
- Receptor on the cell membrane activated (death receptor
- E.g. TNFR & TNF ligand, Fas & Fas Ligand on Cytotoxic T- Lymphocyte
FasL Counterattack
- Cells becoming cancerous express Fas Ligand
- Interact with immune cell, FasR
- Therefore, kill off cells that were intended to kill them
Estrogen & Anti-apoptotic effects
- Estrogen decreases after menopause
- Normally phosphorylates Bad & inactivates it
- Bad-P does not kill osteoblasts
- Non-phosphorylated Bad kills osteoblasts
- Leads to a decrease of osteoblasts & osteoporosis
