chapter Flashcards
architectural planning
noncoding regions
what are thefive major classes of functional non–protein- coding sequences in the human genome
1.Promoter and enhancer
2.Noncoding regulatory RNAs
3.telemeres and centromeres
4.Mobile genetic elements/transposons
5.chromatin structures
percentage of human genome that does not encode proteins
dark matter, 1.5%
Noncoding regulatory RNAs
micro-RNAs (miRNAs) and long noncoding RNAs (lncRNAs)
A major component of centromeres
satellite DNA
The two most common forms of DNA variation in the human genome are
single nucleotide polymorphisms (SNPs) and copy number variations (CNVs)
are variants at single nucleotide positions and are almost always biallelic
SNPs
Heterochromatin
dense, inactive
Euchromatin
disperse and active
are repetitive nucleotide sequences that cap the termini of chromatids and permit repeated chromosomal replication without deterioration of genes near the ends.
telomeres
can be visualized only during mitosis
Chromosomes
act as the locus for the formation of a kinetochore protein complex that regulates chromosome segregation at metaphase
centromeres
are noncoding regions of DNA that initiate gene transcription; they are on the same strand and upstream of their associated gene
Promoters
can modulate gene expression over distances of 100 kb or more by looping back onto promoters and recruiting additional factors that drive the expression of pre–messenger RNA (mRNA) species
Enhancers
may be useful markers if they
happen to be coinherited with a disease-associated polymorphism as a result of physical proximity
SNPs
are a form of genetic variation consisting of different numbers of large contiguous stretches of DNA
CNVs
heritable changes in gene expression that are not caused by variations in DNA sequence
epigenetics
T/F
alterations in DNA sequence cannot by themselves explain the diversity of phenotypes in human populations
True.
e.g. classic genetic inheritance cannot explain differing phenotypes in monozygotic twins
differentiated cells have distinct structures and functions that arise as a result of lineage- specific gene expression programs. Such cell type–specific differences in transcription and translation depend on
epigenetic factors
_______consist of DNA segments 147 bp long that are wrapped around a central core structure of highly conserved low molecular weight proteins called ________
nucleosome, histone
T/F
only the regions that are “unwound” are available for transcription
True
T/F
Histones are static
False. Histones are not static, but rather are highly dynamic
covalent alterations
methylation, acetylation, or phosphorylation
carry out over 70 different histone modifications generically denoted as “marks.”
Chromatin writer” complexes
what are your covalent modifications
Histone methylation
Histone acetylation
Histone phosphorylation
DNA methylation
Chromatin organizing factors
lysines and arginines modified
Histone methylation
whose modifications tend to open the chromatin and increase transcription. In turn, these changes can be reversed by histone deacetylases (HDACs), leading to chromatin condensation
Histone acetylation
Serine residues can be modified by
Histone phosphorylation
modification that typically results in transcriptional silencing
DNA methylation
believed to bind to noncoding regions and control long-range looping of DNA
Chromatin organizing factors
T/F
Unlike genetic changes, many epigenetic alterations (e.g., histone acetylation and DNA methylation) are reversible and amenable to therapeutic intervention
True
These genomic sequences are transcribed but not translated.
Micro-RNA and Long Noncoding RNA
do not encode proteins; they modulate translation of target messenger RNAs (mRNAs)
miRNAs
Generation of microRNAs (miRNAs) and their mode of action in regulating gene function.
miRNA transcribed-> pri-miRNA-> pre-miRNA-> mature double-stranded RNA
cleave or repress translation of mRNA, resulting in posttranscriptiontional silencing.
RISC
mechanisms used by lncRNAs modulate gene expression
gene activation
gene supression
promote chromatin modification
assembly of protein complexes
is transcribed from the X chromosome and plays an essential role in the physiologic X chromosome inactivation
XIST
-XIST itself escapes X inactivation but forms a repressive “cloak” on the X chromosome from which it is transcribed, resulting in gene silencing.
These are linked genetic elements that endow prokaryotes with a form of acquired immunity to phages and plasmids
used for gene editing
makes it possible to selectively edit mutations that cause hereditable disease, or—perhaps more worrisome—to just eliminate less “desirable” traits.
1) clustered regularly interspaced short palindromic repeats (CRISPRs)
2) Cas9 nuclease.
CELLULAR HOUSEKEEPING Involves
a. Plasma Membrane: Protection and Nutrient Acquisition
b. cytoskeleon
c. cell-cell interaction
d. ER and Golgi apparatus
normal housekeeping functions of the cell are compartmentalized within membrane bound intracellular organelles because?
a. potentially injurious degradative enzymes or toxic metabolites can be kept at usefully high concentrations without risking damage to more delicate intracellular constituents
b. maintain low pH and high calcium intracellular environment
c. maintain polarity
New proteins destined for the plasma membrane or secretion are physically assembled in
RER and Golgi
proteins intended for the cytosol are synthesized on
free ribosome
is used for steroid hormone and lipoprotein synthesis and modification of hydrophobic compounds into water-soluble molecules for export.
Smooth endoplasmic reticulum (SER)
are “disposal” complexes that degrade denatured or otherwise “tagged” cytosolic proteins
Proteasomes
They are the site of senescent intracellular organelle breakdown (a process called autophagy) and where phagocytosed microbes are killed and catabolized.
Lysosomes
contain catalase, peroxidase, and other oxida-
tive enzymes
generate hydrogen peroxide
Peroxisomes
Movement—of both organelles and proteins within the cell, as well as the entire cell in its environment—is accomplished by
cytoskeleton
cytoskeleton is composed of
a. filamentous actin (microfilaments)
b. keratins (intermediate filaments)
c. microtubules
are essential to generation and maintenance of cell polarity
cytoskeleton
Loss of polarity could lead to?
disrupt vectorial transcellular transport in the intestine or renal tubule
😤sites of synthesis of heme
😀generate atp
🥹contain important sensors of cell damage to initiate apoptosis
😝last only 10 days
🫣from maternal side
mitochondria
😜fluid bilayers of amphipathic phospholipid
😓have hydrophobic lipid tails that interact with each other
😚remarkably heterogeneous
Plasma membrane
🔫inner membrane leaflet
🔫serve as electrostatic scaffold
Phosphatidylinositol
can be hydrolyzed by phospholipase C to generate intracellular second signals like diacylglycerol and inositol trisphosphate.
polyphosphoinositides
normally restricted to the inner face where it confers a negative charge
when flippedit becomes a potent “eat me” signal during programmed cell death (e.g., apoptosis)
cofactor in blood clotting
Phosphatidylserine
located on the extracellular face of plasma membrane
contribute to including inflammatory cell recruitment and sperm-egg fusion.
Glycolipids and sphingomyelin
The plasma membrane is liberally studded with a variety of proteins and glycoproteins involved in
(1) ion and metabolite transport
(2) fluid-phase and receptor- mediated uptake of macromolecules
(3) cell-ligand, cell-matrix, and cell-cell interactions.
In general, proteins associate with the lipid bilayer by one of four mechanisms.
- integral or transmembrane proteins
- synthesized on free ribosomes
- Proteins anchored by glycosylphosphatidylinositol (GPI)
- Peripheral membrane protein
Many plasma membrane proteins function as large complexes; these may be aggregated either under the control of
- chaperone molecules in the RER
- lateral diffusion in the plasma membrane
Membrane Transport
Passive Diffusion
Carriers and Channels
Small, nonpolar molecules like O2 and CO2 readily dissolve in lipid bilayers and therefore rapidly diffuse across them. they transport through
Passive Diffusion
effective barrier to the passage of larger polar molecules (>75 Da); at 180 Da, for example, glucose is effectively excluded.are also impermeant to ions due to their charge and hydration.
Plasma membrane/lipid bilayer
in tissues responsible for significant water movement (e.g., renal tubular epithelium), thes special integral membrane proteins serves as transmembrane channels
aquaporins
These transporters that move ions, sugars, nucleotides, etc., frequently have exquisite specificities, and can be either active or passive. For example, some transporters accommodate glucose but reject galactose.
Carriers and Channels
create hydrophilic pores, which, when open, permit rapid movement of solutes (usually restricted by size and charge)
Channel proteins
bind their specific solute and undergo a series of conformational changes to transfer the ligand across the membrane; their transport is relatively slow.
Carrier proteins
are used when concentration gradients can drive the solute movement; activation of the channel opens a hydrophilic pore that allows size-restricted and charge-restricted flow.
Channels
are required when solute is moved against a concentration gradient; this typically requires energy expenditure to drive a conformational change in the carrier that facilitates the transmembrane delivery of specific molecules.
Carriers
T/F
active transport of certain solutes (against a concentration gradient) is accomplished by carrier molecules (NEVER channels) at the expense of ATP hydrolysis or a coupled ion gradient.
True
Endocytosis of receptor-ligand pairs often involves
clathrin-coated pits and vesicles
involves membrane invagination to engulf large particles and is most common in specialized phagocytes (e.g., macrophages and neutrophils)
Phagocytosis
can mediate transcellular transport in either apical-to-basal or basal-to-apical directions, depending on the receptor and ligand.
Transcytosis
causes net movement of water out of cells
extracellular salt in excess of that in the cytoplasm
hypertonicity
may be denoted pinocytosis (“cellular drinking”) or phago- cytosis (“cellular eating”)
endocytosis
T/F
Generally, phagocytosis is restricted to certain cell types (e.g., macrophages andneutrophils) whose role is to specifically ingest invading organisms or dead cell fragments.
True
proteins that spontane- ously assemble into a basket-like lattice which helps drive endocytosis
clathrin
In this process, proteins synthesized and packaged within the RER and Golgi apparatus are concentrated in secretory vesicles, which then fuse with the plasma membrane to
EXPEL their contents
exocytosis
is the movement of endocytosed vesicles between the apical and basolateral compartments of cells
Transcytosis
two types of endocytosis
Caveolae-mediated endocytosis
Receptor-mediated endocytosis
are noncoated plasma membrane invaginations associated with GPI-linked molecules
Caveolae
is the major structural protein of caveolae, which, like membrane raft
enriched in glycosphingolipids and cholesterol
caveolin
Internal- ization of caveolae along with bound molecules and associated extracellular fluid is called
cellular sipping
potocytosis
Receptor-mediated endocytosis.
clathrin-coated pits
The vesicles then rapidly lose their clathrin coating and fuse with an acidic intracellular structure called the
early endosome
Defects in receptor-mediated transport of LDL underlie
familial hypercholesterolemia
gives the cell its ability of cells to adopt a particular shape, maintain polarity, organize intracellular organelles, and migrate depends on an intracellular scaffold of structural proteins
Cytoskeleton
three major classes of cytoskeletal proteins
- Actin microfilamentsare 5- to 9-nm diameter fibrils
- Intermediate filaments are 10-nm diameter fibrils
- Microtubules are 25-nm-thick
use G-actin
abundant cytosolic protein in cells
control cell shape and movement
responsible for other functions that depend on actin contraction including vesicular transport, epithelial barrier regulation, and cell migration.
Actin microfilaments and myosin
form ropelike polymers and do not usually actively reorganize like actin and microtubules
tensile strength
bear mechanical stress
link desmosomes and hemidesmosomes
intermediate filament
characteristic tissue-specific patterns of intermediate filament
Vimentin-mesenchymal cells
Desmin-muscle cells
Neurofilaments-neuronal axon
Glial fibrillary acidic protein- glial cells
Cytokeratins- epithelial cells
Lamins-nuclear lamina, define nuclear shape
composed of nonco-
valently polymerized α- and β-tubulin dimers organized into hollow tubes
Serve as mooring lines for molecular motor proteins that use ATP to translocate vesicles
Mediate sister chromatid segregation
Form the core of primary cilia
Microtubules
note: mutations in the proteins of the primary cilia complex lead to forms of polycystic kidney disease
two varieties of these motor proteins of microtubules
kinesins and dyneins
motor protein actin microfilament
myosin
3 types of cell-cell jun tions
Occluding junctions (tight junctions)
Anchoring junctions (adherens junctions and desmosomes)
Communicating junctions (gap junctions)
seal adjacent epithelial cells together
restricts the paracellular (between cells) movement of ions
boundary that separates apical and baso- lateral membrane domain to maintain polarity
Occluding junctions (tight junctions)
mechanically attach cells—and their cytoskeletons—to other cells or the ECM
are formed by homotypic extracellular interactions between transmembrane glycoproteins called CADHERINS, on adjacent cells
Anchoring junctions
are often closely associated with and beneath tight junctions
associated with intracellular actin microfilaments
adherens junctions
note: lost of E-cadherin explains the discohesive invasion pattern of some gastric cancers and lobular carcinomas of the breast
cadherins are linked to intracellular INTERMEDIATE filaments, allowing extracellular forces to be mechanically communicated
desmosomes
the transmembrane connector proteins are called integrins
attach to intermediate filaments
endothelium in the bloodstream or cardiac myocytes in a failing heart
hemidesmosomes
permit the diffusion of chemical or electrical signals from one cell to another.
critical role in cell-cell communication
cardiac myocytes allow cell-to-cell calcium fluxes
Communicating junctions (gap junctions)
is the site for synthesis of all transmembrane proteins and lipids for plasma membrane and cellular organelles, including the ER itself.
the initial site of synthesis for secreted proteins.
endoplasmic reticulum (ER)
assist in folding and retaining proteins in the ER until the modifications are complete and the proper conforma- tion is achieved.
Chaperone molecules
a codon deletion leads to the absence of a single amino acid (Phe508) which results in its misfolding, ER retention and catabolism and therefore reduced surface expression.
CFTR protein in cystic fibrosis
From the RER, proteins and lipids destined for other organelles or extracellular export are shuttled into the ?
Golgi apparatus
Golgi can be recognized as a ___________ on simple hematoxylin and eosin stains
perinuclear hoff
the ____ is relatively sparse and primarily exists as the transition zone
be particularly conspicuous in cells that synthesize steroid hormones
SER
note: In muscle cells, specialized SER called sarcoplasmic reticulum is responsible for the cyclic release and sequestration of CALCIUM ions that regulate muscle contraction and relaxation
responsible for catabolism of long-chained fatty acids.
peroxisomes
include proteases, nucleases, lipases, glycosidases, phosphatases, and sulfatase
containing
roughly 40 different acid hydrolases
Lysosomes
three pathways of lysisomes
- fluid-phase or receptor-mediated endocytosis
- autophagy
- Phagocytosis
play an important role in degrading cytosolic proteins
Proteasomes
evolved from ancestral prokaryotes
contain their own DNA
are encoded by both nuclear and mitochondrial DNA
X-linked, autosomal, or maternally inherited
constantly undergoing fission and fusion
undergoes mitophagy
regulating apoptosis
Mitochondria
mitochondrial functions
Energy generation
intermediate metabolism
cell death
parts of mitochondria
Inner membrane- core matrix space that harbors the bulk of the enzymes of the glycolytic and tricarboxylic acid cycles
Outside the inner membrane/intermembrane space- site of nucleotide phosphorylation
summry of oxidatvie metabolism
mitochondria oxidize substrates to CO2, transferring the high-energy electrons from the original molecule (e.g., sugar) to molecular oxygen. Oxidation of various metabolites drives proton pumps that transfer H+ from the core matrix into the intermembrane space. As the H+ ions flow down their electrochemical gradient and out of the intermembrane space, the energy released is used to generate ATP.
the brown fat that allows rapid substrate oxidation without ATP synthesis that allows tissues with high levels of UCP-1 to generate heat (nonshivering thermogenesis)
thermogenin
increase uptake of glucose and glutamine and switch to aerobic glycolysis, a phe- nomenon called the_____. each glucose molecule is catabolized to lactic acid (even in the presence of adequate oxygen), generating only two net ATP molecules but “spinning off” intermediates
Warburg effect
External cellular injury (toxin, ischemia, trauma) can damage mitochondria, inducing the formation of
mitochondrial permeability transition pores in the outer membrane, making atp generation impossible.
integrate intracellular proapoptotic and antiapoptotic effector signals to generate a final “go” or “no go” signal for apoptosis.
Mitochondria
this happens when permeability transition happens and release cytochrome C into the cytoplasm
The signals that most cells respond to can be classified into several groups. these are
Danger and pathogens
Cell-cell contacts
Cell-ECM contacts
Secreted molecules.
Signaling pathways based on the spatial relationships
Paracrine signaling-
Autocrine signaling-cell affect itself
Synaptic signaling-transmitters
Endocrine signaling-mediator released to the bloodstream
signal that is conveyed is transmitted to the cell via these specific receptor protein
Intracellular receptors
Cell-surface receptors
are generally transmembrane proteins with extracellular domains that bind activating ligands.
Cell-surface receptors
Depending on the receptor, ligand binding can cell surface receptors can:
-Open ion channels
-Activate an associated GTP-binding regulatory protein
(G protein).
-Activate an endogenous or associated enzyme
-Trigger a proteolytic event
associated receptors are typically involved in signaling that drives cellular proliferation; proteolytic or conformation changes are common features of multiple pathways (e.g., Notch, Wnt, and Hedgehog)
G protein–coupled receptors and tyrosine kinase– associated receptors
The interaction of a cell-surface receptor and its ligand can activate signaling through
1.ligand-induced clustering of the receptor (receptor cross-linking)
2. inducing a physical change in receptor structure
note: Either mechanism results in a conformational change in the cytosolic tail of the receptor
Signal Transduction Pathways
- Receptors associated with kinase activity
- G-protein coupled receptors (GPCRs)
- Nuclear receptors
- (Receptor proteins of the Notch family, Wnt protein ligands,Frizzled family receptors)
Modular Signaling Proteins, Hubs, and Nodes
• Enzyme activation (or inactivation).
• Nuclear (or cytoplasmic) localization of transcription
factors (see later).
• Transcription factor activation (or inactivation).
• Actin polymerization (or depolymerization).
• Protein degradation (or stabilization).
• Activation of feedback inhibitory (or stimulatory) loops.
play a key role in organizing intracellular signaling pathways
Adaptor proteins
T/F
Most signal transduction pathways ultimately induce durable effects on cellular function by modulating gene transcription; this occurs through the activation and/or nuclear localization of transcription factors
True
large multiprotein enzymatic complex that is responsible for RNA synthesis.
RNA polymerase
stimulate the activity of signaling pathways and genes that augment cell survival, growth, and division.
Growth factors
Growth factors bind to specific receptors and, ultimately, influence expression of genes that:
• Promote entry into the cell cycle.
• Relieve blocks on cell cycle progression (thus promoting
replication).
• Prevent apoptosis.
• Enhance synthesis of components (nucleic acids, proteins,
lipids, carbohydrates) required for cell division.
sources::Activated macrophages, salivary glands, keratinocytes, many other cells
function: Mitogenic for many cell types; stimulates epithelial cell migration; stimulates formation of granulation tissue
Epidermal growth factor (EGF)
Mesenchymal cells
Stimulates proliferation of endothelial cells; increases vascular permeability
Vascular endothelial growth factor (VEGF)
Activated macrophages, keratinocytes, many other cells
Stimulates proliferation of hepatocytes and many other epithelial cells
Transforming growth factor-α (TGF-α)
Fibroblasts, stromal cells in the liver, endothelial cells
Enhances proliferation of hepatocytes and other epithelial cells; increases cell motility
Hepatocyte growth factor (HGF) (scatter factor)
Platelets, macrophages, endothelial cells, smooth muscle cells, keratinocytes
Chemotactic for neutrophils, macrophages, fibroblasts, and smooth muscle cells; activates and stimulates proliferation of fibroblasts, endothelial cells, and other cells; stimulates ECM protein synthesis
Platelet-derived growth factor (PDGF)
Macrophages, mast cells, endothelial cells, many other cell types
Chemotactic and mitogenic for fibroblasts; stimulates angiogenesis and ECM protein synthesis
Fibroblast growth factors (FGFs) including acidic (FGF-1) and basic (FGF-2)
Platelets, T lymphocytes, macrophages, endothelial cells, epithelial cells, smooth muscle cells, fibroblasts
Chemotactic for leukocytes and fibroblasts; stimulates ECM protein synthesis; suppresses acute inflammation
Transforming growth factor-β (TGF-β)
Fibroblasts
Stimulates keratinocyte migration, proliferation, and differentiation
Keratinocyte growth factor (KGF)
by virtue of their proliferative effects, gain-of-function mutations convert them into onco- genes that lead to unfettered cell division and can be precur- sors to malignancy
proto-oncogenes
recepter that is overexpressed in a subset of breast cancers.
ERB-B2 receptor
has mitogenic effects on hepatocytes and most epithelium including biliary, lung, kidney, breast, and skin.
Hepatocyte Growth Factor (HGF).
acts as a morphogen in embryonic development
HGF
is frequently overexpressed or mutated in tumors, particu- larly renal and thyroid papillary carcinomas.
MET
is the major angiogenic factor after injury and tumors
VEGF-A
are involved in embryonic vessel development
VEGF-B and PlGF
stimulate both angiogenesis and lymphatic development (lymphangiogenesis).
VEGF-C and VEGF-D
is the most important inducer of VEGF production
hypoxia
is highly expressed in endothelium and is the most important for angiogenesis
VEGFR-2
increased levels of soluble VEGFR-1 (also known as s-FLT-1) in pregnant women may cause
preeclampsia (hypertension and proteinuria)
has the most widespread distribution and is commonly referred to simply as TGF-β
TGF-β1
TGF-β signaling has multiple—and often opposing—effects, depending on the tissue type and any concurrent signals. Agents with such multiplicity of effects are called
pleiotropic
stimulates the production of collagen, fibronectin, and proteoglycans and inhibits collagen degradation
for scar formation
drives fibrosis in lung, liver, intestines, and kidneys
inhibiting lymphocyte proliferation and activity of other leukocytes
TGF-β
ECM functions as a
- Mechanical support
- Regulator of cell proliferation
- Scaffolding for tissue renewal
- Foundation for establishment of tissue microenvironments
The ECM occurs in two basic forms:
interstitial matrix and basement membrane
occupies the spaces
between stromal cells within connective tissue and between parenchymal epithelium and the underlying supportive vascular and smooth muscle structures in some organs.
Interstitial matrix.
what are found in your BASEMENT MEMBRANE
• Type IV collagen
• Laminin
• Proteoglycan
what is in the INTERSTITIAL MATRIX
• Fibrillar collagens
• Elastin
• Proteoglycan and hyaluronan
Components of the Extracellular Matrix
- Fibrous structural proteins (collagens and elastin)
- Water-hydrated gels (proteoglycans and hyaluronan)
- Adhesive glycoproteins
types of collagen
- Fibrillar collagens (type 1,2,3,5)
- Nonfibrillar collagens (type 4)
Genetic defects, including collagen and lysyl hydroxylase mutations, cause diseases such as
osteogenesis imperfecta and certain forms of Ehlers-Danlos syndrome
note: lysyl hydroxylase, is dependent on vitamin C, explaining why children with ascorbate deficiency have skeletal deformities and why individuals of any age with vitamin C deficiency heal poorly and bleed easily.
The ability of tissues to elastically recoil and return to a baseline structure after physical stress is conferred by
important in cardiac valves and large blood vessels, which need to accommodate recurrent pulsatile flow, as well as in the uterus, skin, and ligaments.
elastin
confer resistance to compressive forces; in joint cartilage, proteo- glycans also provide a layer of lubrication between adjacent bony surfaces
Proteoglycans and Hyaluronan
The sequence of events that results in cell proliferation is called the cell cycle; it consists of
G1 (gap 1), S (DNA synthesis), G2 (gap 2), and M (mitotic) phases; quiescent cells that are not actively cycling are in the G0 (gap 0) state
a major constituent of basement membrane
laminin
a major constituent of basement membrane
laminin
a major component of the interstitial ECM
fibronectin
Cell cycle progression is chaperoned by proteins called
cyclin
the checkpoint that monitors DNA integrity before irreversibly committing cellular resources to DNA replication.
G1-S
the restriction point insures that there has been accurate genetic replication before the cell actually divides.
G2-M
If the genetic derangement is too severe to be repaired, cells either undergo apoptosis or enter a nonreplicative state called
senescence
Enforcing the cell cycle checkpoints is the job of
CDK inhibitors (CDKIs)
have the dual property of being able to self renew and to give rise to differentiated cells and tissues.
Stem cells
cells that can give rise to the full range of differentiated tissues
totipotent
only have the capacity to replace damaged cells and maintain cell populations within the tissues where they reside.
adult stem cells
Under conditions of homeostasis, stem cells are main- tained by self-renewal, which can involve two types of cell division:
- Asymmetric division
- Symmetric division
occurs when both daughter cells retain self-renewal capacity
Symmetric division
refers to cell replication in which one
daughter cell enters a differentiation pathway arise to mature cells, while the other remains undifferentiated
Asymmetric division
two varieties of stem cells
- Embryonic stem (ES)
- tissue stem cells
are the most undifferentiated.
They are present in the inner cell mass of the blastocyst, have virtually limitless cell renewal capacity
Embryonic stem (ES)
also called adult stem cells, are found in intimate association with the differentiated cells of a given tissue.
Tissue stem cells
what protects the tissue stem cells by forming microenvironments?
stem cell niches
cells continuously replenish all the cellular elements of the blood as they exit the circulation, senesce, or are otherwise consumed
Hematopoietic stem cells
These are multipotent cells that can differentiate into a variety of stromal cells including chondrocytes (cartilage), osteocytes (bone), adipocytes (fat), and myocytes (muscle).
mesenchymal stem cells
pluripotent stem cells can develope into
pancreatic islet cells
Hematopoietic cells
Cardiomyocytes
Neurons
Hepatocytes
note: The pluripotent cells of the inner cell mass, known as ES cells, can be induced to differentiate into cells of multiple lineages.
ES: from fertilized blastocyst
total volume and number per cell of mitochondria
22%, 1700/cell
