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8/11/2019 Cell Replication (Telomeres, Biology)
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Science is knowledge based on experimentation
Science cannot answer ALL the questionsScience evolves as technology evolves
Science empowers us with knowledge, including knowledge of what we do notknow
Science progresses, it is continuously revised and learned
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NOT an opinion or idea
Based on RESULTS!Ties together the results of numerous studies
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How Does Science Affect YourLife?
Knowledge is power to solve problemsProblems can be solved only if we makea conscious effort at understanding theworld around us
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Redi and the Disproof of“Spontaneous Generation”
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Scientific Method
Observations and factsHypotheses and predictionsTestingEvaluation and interpretation of resultsConclusions
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Semmelweis and Childbed Fever:Mortality Rates
Observation:Mortality rates higher in women thatgave birth in HIS Hosiptal compared toother hospitalsMortalilty rates higher in Division 1
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Semmelweis and Childbed Fever:Characteristics of Division 1
Hypotheses:MiasmaOnly male doctors
Rougher .Different birthing position
Laying on their back
Next to autopsies laboratoryCadaverous particles
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Semmelweis and Childbed Fever:Testing:
MiasmaIncrease ventilation
Only male doctorsRougher. Gentler handling.
Different birthing positionLaying on their back. Change position toside.
Next to autopsies laboratoryCadaverous particles. Hand washing with
chlorine.
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Semmelweis and Childbed Fever:Results and Conculsion:
Only chlorine hand washing reducedrates of childbed fever.Cadaverous particles caused childbedfever
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Consequences
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The property that distinguishes live things fromdead ones
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Composition of Earth Crustand Human Body
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Composition of Earth Crustand Human Body
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Life (E. Schrondinger, 1944 )
All living things avoid decay into equilibrium
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All Cells Have a Unique InternalEnvironment NOT in Equilibrium With the
Outside WorldLife=ability to maintain a unique internalenvironment at an energy cost.
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Unit of Life is the Cell
Inside a cell, life performs all the chemicalreactions necessary to avoid decay intoequilibrium
Make all their parts from simple raw materialsfound in the environmentFuel decay avoidance by taking advantage ofenvironmental sources of energy
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17
Life, single cells,prokaryotic cells
Macro-fossils
EG Nisbet & NH Sleep, 2001. The habitat and nature of early life. Nature 409:1083-1091
Eukaryotic cells,still single cellorganisms
Four Eons200,000 years ago.Homo sapiens
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NucleusMitochondria
Prokaryote Eukaryote
EXCLUSIVELY UNICELLULAR
UNICELLULAR andMULTICELLULAR
Three Domains of life.Two basic cell plans.
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oese na ys s o osomaRNA
From this table,Woese and Fox inferthe existenceofthree primary branches in thetree oflife.From this table,Woese and Fox inferthe existenceofthree primary branches in thetree oflife.
From this table, Woese and Fox infer the existence of three primary branches in the tree of life.
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The Tree of Life
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Flagella
Cell wall
Membrane
Chromosome,Circular
Ribosomes
Two types of cells, prokaryotes and eukaryotes
They both perform all of the life functions, usingdifferent organization but with the same basic
components.
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All cells have many features incommon, including:
A cell membrane or plasma membrane (phospho-lipid bilayer)DNA chromosome(s)Ribosomes for protein synthesisCytoplasm in the cell: water with many dissolvedmolecules
About 500 genes are shared in all three Domains oflife
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Differences
ProkaryotesNo nucleusNo endomembrane
system (ER, Golgi,lysosomes)No mitochondria andchloroplasts
Peptidoglycan cellwall
EukaryotesNucleusEndomembranesystem (ER, Golgilysosomes)Mitochondria andchloroplastsNo peptidoglycancell wall
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Cellular Membranes
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Functions of Cellular MembranesEnclose the cytoplasmControl movement of ions and molecules,therefore maintains the chemical environmentinside the cellOrganize enzymesDetect and allow responses to signals from theenvironmentPromotes recognition and adhesion between cellsand between cells and the extracellular matrix
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Cellular Membranes are Semi-PermeableThis Characteristic Is Essential For Life
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Membranes Are Made of Phospholipids.
Phospholipids are amphipatic. One end of the molecule ishydrophobic and the other id hydrophilic
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The Plasma Membrane Is Composedof a Phospholipid By-layer
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Small, uncharged substances pass through;large and/or charged substances do not
Permeability of Phospholipid By-layers
For these there aretransport proteins
High permeability
Low permeability
Small polar moleculespass through moreslowly
Small nonpolar moleculespass through rapidly
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So, How Does Anything That Is NotPermeable Go In and Out?
Proteins help!!!
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Active and PassiveTransport
Passive transport follows an ion/moleculeconcentration gradient and does not requireenergy input
Active transport translocates ions/moleculesagainst their concentration gradient andtherefore requires energy input
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Types of Transmembrane MovementMotion against concentrationgradient. Requires input ofenergy. ATP
Allows for maintenance ofunique intracellular
environment
Addi i l F i f
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Additional Functions ofTransmembrane Proteins
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Some Cells Have a Cell Wall
Cell walls vary in composition. We will only discuss bacteria cell wall.
f
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Two types of Bacteria Cell Wall
Peptidoglycan, both in Gram + and Gram -. Complex network of small peptidesand sugars. NOT to be confused with the plant cell wall. Cellulose. Polymer ofglucose.Lipopolysaccharide is the outer wall specific of Gram Negative bacteria.
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The Cell Wall Is Essential toBacteria
Protective functionHelps bacteria attach to substratesOur immune system has specialized
molecules that recognize peptidoglycan andlipopolysaccharidePenicillin blocks the bacterial enzymenecessary for cell wall synthesis. Causes
bacterial cells to explode
E h i hi li
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Escherichia coliin lab for several weeksGram negativeEnteric. Normal part of ourintestinal flora.Can cause disease if gets out
of digestive tract. ie. Urinaryinfection, nosocomial infectionsOR if it acquires toxic genesfrom other species
BEST studied bacterium. Modelsystem. Discovery: geneticcode, glycolisis, regulation ofgene expression
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CytoplasmCytoplasm is the watery medium where all the molecules
dissolved
Eukaryotic cell
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Cytoplasm numbers
Bacterial cell: 70% water, 30% proteins (egg white is90% water and 10% proteins), nucleic acids, ions andother molecules.Cytoplasm has a very concentrated consistency andis a very busy place!Estimated in E. coli (1 mm diameter):
4300 proteins.191 RNA1220 types of small molecules
1550 different chemical reactions50% of the molecules dedicated to making other proteins.25% dedicated to producing ATP
A C ll I B Pl !
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A Cell Is a Busy Place!
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Cytoskeleton
Animal cells do not have a cell wall. Theyuse an internal scaffolding (cytoskelton) toperform different functions.
A cell’s structure and movements isdetermined by the cytoskeletonHighly organized protein fibers.Both prokaryotes and eukaryotes havecytoskeleton, made of different types ofproteins. Less developed and understood inprokaryotes
Cytokeletal Fibers Are Made
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Cytokeletal Fibers Are Madeof Building Blocks
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Eukaryote Cytoskeleton
COMPONENTS Actin cortex. Polymerization of actinprotein monomers.Microtubules. Polymerization of a and b tubulin proteinsIntermediate filaments. Up 70 proteins
polymerize to make these filaments.
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Genomes and Nucleus
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The Genetic Material
All the cells chemical reactions are programmed by amaster regulator, the genomeThe genome is made of DNA (some viruses haveRNA genomes, but they will be discussed later)
DNA is organized in structures called chromosomesDNA has the information for the synthesis of a cell’
sentire set of proteinsDNA instructs the cell on which proteins to make,
when to make them, where to make them.The language used by DNA to direct a cell’
s functionsis UNIVERSAL
Chromosomes
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Prokaryote Eukaryote
Additionalplasmids may be present
+ histones
NO histones
P k t l
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Prokaryotes: no nucleusNucleoid regionWell packaged. Half millimeter circle fits in aspace less than one hundredth its size. (averagebacterial cell between .5 and 5 mm.
Eukaryotic cells have a
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Nucleus & nucleolusHouse DNASite of transcriptionNucleolus: make ribosomes
The cell ’
s hard drive
Eukaryotic cells have amembrane-bound nucleus
Eukaryotic DNA packaging
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Eukaryotic DNA packaging
All human chromosomes would stretch to 6 feetEukaryotic cell size averages 10 mm
Eukaryotic nucleus size, few mm
Eukaryotic DNA isassociated with basic
proteins calledhistones.
Prokaryotic DNA isnot associated withhistones.
The Endomembrane System:
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The Endomembrane System:Involved in the Synthesis Delivery of
Molecules Endoplasmic reticulumGolgi apparatus
Exocityc vesciclesLysosmesEndosomes
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The Endomembrane System:
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Endocytosis and Exocytosis
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https://www.youtube.com/w
atch?v=DuDmvlbpjHQ
E d l i R ti l (ER)
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Endoplasmic Reticulum (ER)Smooth ER: Lacks ribosomes.Involved in synthesis of lipids.
Rough ER:Has ribosomesattached. Interconnected flattenedsacs. Functions to make moremembrane and to make proteinsthat are inserted in the plasmamembrane, or shipped elsewhere.
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Exocytosis: Secreting Molecules
How Do the Vescicles Know
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How Do the Vescicles KnowWhere to Go?
Cytoskeleton!!!!
vescicle trafficking cartoon via youtube
vescicle trafficking in vitro via youtube
f
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Endocytosis: Uptake of Molecules and Cells
Lysosomes
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LysosomesLysosomes are thewaste disposal /recycling system of thecellThey sequesterhazardous enzymes thatdigest food, destroyinvaders, or dispose ofailing mitochondria orchloroplasts.Endosomes (vesiclesresulting fromendocytosis, fuse withlysosmes. In the
resulting fusion vesicledigestion occurs
Mechnikov, best remembered for his pioneering
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, p gresearch into the immune system, received the
Nobel Prize in Medicine in 1908, shared withPaul Ehrlich, for his work on phagocytosis,
© 2003 Nature Publishing Group Conner, S. D. & Schmid, S. L. Regulated portals ofentry into the cell. Nature 422, 37 – 44 (2003) doi:10.1038/nature01451. All rightsreserved.
Phagocytes
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PhagocytesEndocytosis is used by a family of immune
cells known as phagocytes that employ thismechanism to destroy pathogens
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http://www.youtube.com/watch?v=Z_mXDvZQ6dU
Amoeba’s Dinner
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http://www.youtube.com/wat
ch?v=aWItglvTiLc
Neutrophil Fights Bacteria
Ribosomes and Protein
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Ribosomes and ProteinSynthesis
Proteins are synthesized by small structurescalled ribosomes.Ribosomes are composed of proteins and RNA
Ribosomes are composed of two subunits
Protein Synthesis in Prokaryotes
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Protein Synthesis in Prokaryotes
Flagella
ChromosomeCircular, at most 10 Mb
Cytoplasm
Ribosomes
Ribosomes are localized in the cytoplasmHow proteins are targeted to the right localization is not well known
Protein Synthesis and
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Protein Synthesis andTransport in Eukaryotes
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Mitochondria and Chloroplasts
Plants
All eukaryotic cells,including plants
Photosynthesis
Aerobic Respiration
Mitochondria and Chloroplasts
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Mitochondria and Chloroplasts
Note: both mitochondria and chloroplasts havecompartments surrounded by a double membrane.This inter-membrane space is essential for the building of aproton gradient used to release energy for the synthesis of
ATP during aerobic respiration and photosynthesis.
https://www youtube com/w