Control of Cell Division and Cell Growth Flashcards
Organ and body size are determined by three fundamental processes:
- Cell growth
- Cell division
- Cell survival
The extracellular signal molecules that regulate cell growth, division, and survival are generally _____ , _____ , or _____ .
- Soluble secreted proteins
- Proteins bound to the surface of cells
- Components of the extracellular matrix
The extracellular signal molecules that regulate cell growth, division, and survival can be divided into three major classes:
- Mitogens
- Growth Factors
- Survival Factors
Stimulate cell division, primarily by triggering a wave of G1/S-Cdk activity that relieves intracellular negative controls that otherwise lock progress through the cell cycle.
Mitogens
Stimulate cell growth by promoting the synthesis of proteins and macromolecules and inhibiting their degradation.
Growth Factors
Promote cell survival by suppressing the form of apoptosis
Survival Factors
The rate of proliferation depends on the _______ .
The availability of nutrients in the environment
The cell of a multicellular organism divide only when the organism ______ .
Needs more cells
The first mitogens to be identified
Platelet-derived growth factor (PDGF)
Is prepared by removing the cells from blood without allowing clotting to occur
Plasma
Is prepared by allowing blood to clot and taking the cell-free liquid that remains
Serum
PDGF can stimulate many cell to divide including _____ , _____ , and _____ .
- Fibroblasts
- Smooth muscle cells
- Neuroglial cells
Stimulates division of epidermal cells, including epithelial and nonepithelial cells.
Epidermal Growth Factor
Inhibitory signal proteins that inhibits the proliferation of several cell types by blocking cell-cycle progression in G1.
Transforming growth factor β (TGBβ)
A state in which the cell-cycle control system is completely dismantled
Terminally differentiated G0 state
Most of the _____ and _____ _____ cells are in a terminally differentiated G0 state.
- Neurons
- Skeletal Muscle Cells
A monomeric GTPase that activates the mitogen-activated protein kinase (MAP kinase) cascade, leading to increased production of transcription regulatory proteins like Myc.
Ras
A signaling pathway activated by Ras
Mitogen-Activated Protein (MAP) Kinase Cascade
A transcription regulatory protein that promote cell-cycle entry by increasing the expression of genes encoding G1 cyclins, thereby increasing G1-Cdk activity.
Myc
Bind to specific DNA sequences in promoters of genes that encode for proteins required for S-phase entry.
E2F Proteins
Protein that inhibit the expression of E2F-dependent gene by binding to E2F in absence of mitogenic stimulation
Retinoblastoma Protein (Rb) Family
DNA damage can occur as a result of ______ , ______ , or ______ .
- Spontaneous chemical reactions in DNA
- Errors in DNA Replication
- Exposure to radiation or certain chemicals
The cell-cycle control system can detect DNA damage and arrest the cycle at either of two transitions:
- Start (prevents entry into S phase)
- G2/M Transition (prevents entry into mitosis)
Protein kinases that are phosphorylated by ATM and ATR in occurrence of DNA damage
Chk1 and Chk2
A pair of protein kinases that are activated by a signaling pathway initiated by DNA damage
ATM and ATR
A phenomenon where proliferation slows down and finally halts, and he cells enter a non-dividing state from which they never recover.
Replicative Cell Senescence
A type of human cell that typically undergo about 25–50 population doublings in culture before entering a nondividing state
Fibroblasts
Th repetitive DNA sequences and associated proteins at the ends of chromosomes
Telomeres
The enzyme responsible for synthesizing telomeric DNA sequences and forming protective cap structures at chromosome ends
Telomerase
Why do human fibroblasts experience telomere shortening with every cell division?
Because they do not produce telomerase.
What cellular mechanism is activated when exposed chromosome ends are detected as DNA damage in human cells?
p53-dependent cell-cycle arrest
What effect does overexpression of Myc have on cells?
Stimulates excessive cell growth and proliferation, promoting cancer development.
What cell-cycle inhibitor protein is often produced in response to excessive mitogenic stimulation?
Arf
What protein does Arf inhibit, which normally promotes p53 degradation?
Mdm2
What happens to p53 levels when Arf is activated?
p53 levels increase, inducing either cell-cycle arrest or apoptosis
What would happen to cell size if cells proliferated without growing?
Cells would progressively get smaller.
Extracellular signal molecules that stimulate cell growth in animal cells
Growth Factors
What is the role of mitogens in cell proliferation?
stimulate cell division
What intracellular signaling enzyme is activated by growth factor receptors and leads to TOR activation?
Phosphoinositide 3-kinase (PI 3-kinase)
A protein kinase activated by TOR which phosphorylates ribosomal protein S6, increasing the ability of ribosomes to translate mRNA that encode ribosomal components.
S6 kinase
Which translation initiation factor is indirectly activated by TOR?
eIF4E
If cells
grow too slowly, they will ________ with each division, and if they grow too fast,
they will _______ with each division.
- Get smaller
- Get larger
What types of animal cells can grow significantly after permanently withdrawing from the cell cycle?
Muscle cells and nerve cells
A specific type of neuron in mammals that has its size regulated by the amount of nerve growth factor (NGF)
Adult sympathetic neurons
