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Cell Interactions and Stem Cells• Recognize the importance of cell interactions, cell signaling and cell-cell
interactions, for coordination of functions in a multi-cellular organism. • Learn the three stages of cell signaling, the different types of first messengers
(external signals including hormones), internal messengers, and different cellular responses.
• Explain why different body cells respond in specific yet different ways to the same chemical signal.
• Review the steps of early embryonic development from the fertilized egg to a multi-cellular organism with differentiated cells.
• Distinguish between stem, progenitor, and differentiated cells in terms of ability to self renew (replicate) and gene expression.
• Define and explain the difference between totipotent, pluripotent, and multi-potent cells with examples.
• Learn the three general sources of stem cells, and how they differ.
Figure 2.3
Cell Communication
Make multi-cellular life possible through coordination of cellular activities
Two broad types of cell interaction1) Cell Signaling at a distance2) Cell-cell interactions close proximity
Defects cause certain inherited disorders
Cell signaling: allows cells to receive and respond to surrounding biochemical signals
The same basic cellular function is involved in:• Sensing pain • Inflammation & wound healing• Diabetes• Anxiety• Learning & memory• Psychoactive substances- caffeine, nicotine, marijuana, etc…
Figure 2.19
Cell Signaling
Reception
Signal Transduction
Response
Figure 2.3
Signal TransductionThe process of transmitting a signal from the
environment to a cell
- Receptor binds to “first messenger”- Interacts with regulator
- Causes an enzyme to produce “second messenger”
- Elicits cellular response, which is typically enzyme activation
Cell Signaling
Leads to • Specific response to a specific signal• Amplified responses due to cascade
http://www.learner.org/courses/biology/units/cancer/images.html
Cell signaling in apoptosis http://www.youtube.com/watch?v=hqhxnWty5jc&feature=relat
edStages of Apoptosis
• Destroy enzymes the replicate and repair DNA• Activate enzymes that cut DNA into similar sizes• Disassemble the cytoskeleton and the nuclear lamina,
condense DNA• Signal the mitochondria to increase caspase activity and
end the energy supply• Abolish the cell’s ability to adhere to other cells• Attract phagocytes to remove the cell remnants
The response of a particular cell to a signal depends on its particular collection of receptor proteins, and other
cellular proteins needed to carry out the response
Insulin Signaling
Figure 2.20
Cell-cell interactions: - Adhesion proteins
- Gap junctions
The inner life of the cellshttp://www.studiodaily.com/main/searchlist/6850.html
orhttp://www.dnatube.com/video/551/The-Inner-Life-Of-A-Cell-HQ
Stem CellsFrom a Fertilized egg (zygote) to a multi-cellular organism
Sperm cell
NucleicontainingDNA
Egg cell
Fertilized eggwith DNA fromboth parents
Embyro’s cells with copies of inherited DNA
Offspring with traitsinherited fromboth parents
Inner Cell Mass
Figure 2.3
Stem Cells
All cells in the human body descend from Embryonic stem cells via mitosis and differentiation
Cells differentiate down cell lineages by differential gene expression
Adult Stem cells are present throughout life and provide growth and repair
Figure 2.3
Stem Cells
A stem cell divides by mitosis- Produces daughter cells that retain the ability to divide and some that specialize
Progenitor cells do not have the capacity of self-renewal
Figure 2.20
Figure 2.3
Stem & Progenitor Cells
Described in terms of their developmental potential
Totipotent – Can give rise to every cell typeEmbryonic Stem (ES) Cells
Pluripotent – Have fewer possible fates
Multipotent – Have only a few fates Daughters of Pluripotent cells
Figure 2.3Figure 2.23
Pluripotentcells
Totipotent(Embryonic stem cells)
Multipotentcells
Differentiation produces a variety of cell types, each expressing a different combination of genes
Muscle cell Pancreas cells
Blood cells Nerve cell
Figure 2.3
Stem Cells in Health CareThere are 3 general sources of human stem cells
1) Embryonic stem cells – Created in a lab dish using the inner cell mass (ICM) of an embryo
2) Adult stem cells – Tissue-specific or somatic stem cells
3) Induced pluripotent stem (iPS) cells – Somatic cells reprogrammed by genes or chemicals to differentiate into any of several cell types
Under the right conditions, cultured stem cells derived from either source can differentiate into specialized cells.
Stem Cells uses
• Therapeutic- Tissues & OrgansOrgan engineering
https://www.ted.com/talks/anthony_atala_growing_organs_engineering_tissue?language=en
• Reproductive- Organism (Animal Cloning)
Induced Pluripotent Stem Cells (iPSC)
Figure 2.24
Stem Cells in Health Care
Figure 2.22
Organ engineeringhttps://www.ted.com/talks/anthony_atala_growing_organs_engineering_tissue?language=en
https://www.ted.com/talks/anthony_atala_printing_a_human_kidney?language=en
Cloning of a Mammal
In 1997 by Ian Wilmut
http://learn.genetics.utah.edu/units/cloning/whatiscloning/