Cell Cycle Flashcards
Name the stages of Cell Cycle?
G1
S
G2
M
What is the cell what happens in G1
Active metabolism and accumulation of building blocks and energy.
The cell grows and synthesis all protein necessary,
Make glucose
What happen in S phase
DNA is synthesizes
DNA replication occurs- each DNA molecule produce identical copy, centrosomes is duplicated
What happens in G2
Active metabolism and protein synthesis, duplication of organelles
What happen in Mitosis
Cell division and end up with two cells
What are the phases of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
What happens during prometaphase?
- Chromosomes continue to condense
- Mitotic spindle microtubules attach to kinetochores
- centrosomes move toward opposite poles
What happens during metaphase?
- Mitotic spindle is fully developed, centrosomes are at apposite pole of the cell
- chromosomes are lines up. At the metaphase plate
- Each sister chromatic is attached to a spindle fiber originating from opposite poles
What happens in Anaphase?
- Cohesin proteins binding the sister chromatids together break down
- Sister chromatids (now called chromosomes) are pulled toward opposite poles
- non-kinetochore spindle fibers lengthen, Elongsting the cell
What happens in telophase?
- Chromoseomes arrive at opposite poles and begin to decondense
- nuclear envelope material surround each set of chromosomes
What happens during G0- resting?
A period in the cell cycle in which cell exist in a quiescent state.
What is a quiescent state?
The cell is neither dividing nor preparing to divide
The majority of cells in the human body have irreversible withdrawn from the cell cycle into either of two thing?
- a terminally differentiated state (neurons, myocytes or surface epithelial cells of skin and mucosa) a do not re-enter the cell cycle
- a reversible quiescent G0 phase (stem cells, glia cells, hepatocytes or thyroid follicular cells) - capable to return to the cell cycle
What type of cells are stuck in the terminally differentiated state?
Neurons
Myocytes or surface epitheirak cells of skin and mucosa
What cells are able to re-enter the cell cycle?
Stem cells
Glia cells
Hepatocytes
Thyroid follicular cells
How does control of the cell cycle occur? (3)
- Regulation at internal checkpoints.
- Regulatory molecules
- Regulation by external signals
What Happens in Prophase?
- Prophase- chromosomes condense and become visible
- splinter fibers emerge from the centrosome
- nuclear envelop breaks down
- Nucleous Disappear
How many check points does the cell cycle have and where are they?
3 check points
1. G1
G2
M
What happens in the G1 checkpoint?(4)
The cell check for
- Cell size
- Nutrients
- Growth factors
- DNA damage
What happens in the G2 checkpoint? (2)
The cell checks for
- Cell size
- Accurate DNA replication
What happens in the M checkpoint?
The cell check for chromosome attachment to the spindle
How is the cell cycle controlled through regulatory molecules?
- Positive regulation- cycling and cdk
2. Negative regulation - Rob, p53, and p21
How does positive regulation of the cell cycle through cycling and cdk happens?
- changes of different cycling throughout the cell cycle
- direct correlation between cycling accumulation and the three major cell cycle checkpoints
- Harp decline of cycling is degraded by cytoplasmic enzymes
- Cyclins are only active when bond to the respective cyclin- dependent kinase
What enzyme is responsible for degrading Cyclin?
Cytoplasmic enzymes
What does Cyclin have to be bond to in order for it to be active?
Cyclin-dependent kinase
What does Rb protein do and How does negative regulation through Rb regulates the cell cycle?
Rb- retinoblastoma protein: prevent initiation of the cell cycle in G1 phase.
How?
Unphosphorylated Rb binds transcription factor E2F. Therefore E2F cannot bind the DNA and transcription is blocked.
What is E2F responsible for?
Controls transcription of 500 genes necessary for transition into G2
What happens when Rb gets phosphorylated?
Cell growth triggers the phosphorylation of Rb. Phosphorelated Rb releases E2F, .which binds the DNA and turns on gene expression, this advancing the cell cycle.
Is p53 a transcriptional inhibitor or activator?
Inhibitor.
What is the end results of M phase?
Formation of 2 daughter cells!
How does p21 regulates the cell cycle?
P21 prevents cell cycle progression
How does p21 prevent cell-cycle progression? (2)
- Inhibiting the activity of Cyclin E associated CDK2
2. Therefore preventing E2F mediated gene transcription and cell cycle progression
What is mitogens?
It’s an external stimuli that causes the cells to proliferate (return to G1 if in G0)
How does mitogen induce the cell to proliferate?
- Can be provided by extracellular matrix (intergins)
2. Can be extracellular signal from more distant sources
Mitogens
Intergins:
- cell to matrix contact is called _______
- cell to cell contact is called ______
Extracellular Distance sources:
- ___________ EGF, VEGF, NGF, FGF
- ___________ IL-1, IL-6
Mitogenic
Antimitogenic (contact inhibition)
Growth factors
Cytokines
Name the 6 types of Growth factors
- Platelet- derived growth factor (PDGF)
- Epidermal growth factor (EGF)
- Fibroblast growth factor (FGF)
- Insulin-like growth factor 1 (IGF-1)
- Vascular endothelial growth factor (VEGF)
- Nerve growth factor (NGF)
PDGF is present in the ____ of _____ from which it is released during activation - participates in ______ ______
EGF stimulated the _______ of epithelial cells and some other cells. It acts primarily in ________
FGF are a family of at lease ___(how many) proteins that act in four different _____ (type of receptors) and they stimulate ______ (type of cell) and other types of cells
a-granules of platelets , participate in wound healing
Proliferation, tissue of origin
22 proteins, tyrosine kinase receptors, stimulate fibroblasts
IGF-1 is released from ____ in response to _____ hormone
VEGF produced by cells that stimulates ____ and _____ (new blood vessel formation)
NGF stimulated the growth and differentiation (but not mitosis) of ____ ______ neurons (type of neurons)
Liver, growth
Vasculogenesis, angiogenesis
Postganglionic sympathetic neurons
Abnormal uncontrolled cell cycle over period of time can lead to development of ____
Neoplasms (tumors)
Note: Tumors are group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely
What are the 6 hallmarks of cancer, which are required to produce a malignant tumor?
- Cell growth and division absent the proper signals
- Continuous growth and division even given contract signals
- Avoidance of programmed cell death
- Limitless number of cell divisions
- Promoting blood vessel construction
- Invasion of tissue and formation of metastases
What are oncogenes?
The are mutated normal genes that encode positive cell cycle regulators that chases a cell to become cancerous.
What are Tumor suppressor genes?
Genes that encode for negative regulator proteins that will suppress uncontrolled cell division like Rb, p53,p21
How does p53 regulates the cell cycle?
- has the ability to repress transcription and to promote apoptosis through direct interaction with apoptosis regulators in the cytosol
- indices cell cycle arrest.
