Cell Replication (Telomeres, Biology)

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



NOT an opinion or idea

Based on RESULTS!Ties together the results of numerous studies



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



Redi and the Disproof of“Spontaneous Generation”



Scientific Method

Observations and factsHypotheses and predictionsTestingEvaluation and interpretation of resultsConclusions



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



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



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.



Semmelweis and Childbed Fever:Results and Conculsion:

Only chlorine hand washing reducedrates of childbed fever.Cadaverous particles caused childbedfever



Consequences



The property that distinguishes live things fromdead ones



Composition of Earth Crustand Human Body



Composition of Earth Crustand Human Body



Life (E. Schrondinger, 1944 )

All living things avoid decay into equilibrium



All Cells Have a Unique InternalEnvironment NOT in Equilibrium With the

Outside WorldLife=ability to maintain a unique internalenvironment at an energy cost.



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



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



NucleusMitochondria

Prokaryote Eukaryote

EXCLUSIVELY UNICELLULAR

UNICELLULAR andMULTICELLULAR

Three Domains of life.Two basic cell plans.



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.



The Tree of Life





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.



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



Differences

ProkaryotesNo nucleusNo endomembrane

system (ER, Golgi,lysosomes)No mitochondria andchloroplasts

Peptidoglycan cellwall

EukaryotesNucleusEndomembranesystem (ER, Golgilysosomes)Mitochondria andchloroplastsNo peptidoglycancell wall



Cellular Membranes



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



Cellular Membranes are Semi-PermeableThis Characteristic Is Essential For Life



Membranes Are Made of Phospholipids.

Phospholipids are amphipatic. One end of the molecule ishydrophobic and the other id hydrophilic



The Plasma Membrane Is Composedof a Phospholipid By-layer



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



So, How Does Anything That Is NotPermeable Go In and Out?

Proteins help!!!



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



Types of Transmembrane MovementMotion against concentrationgradient. Requires input ofenergy. ATP

Allows for maintenance ofunique intracellular

environment

Addi i l F i f



Additional Functions ofTransmembrane Proteins



Some Cells Have a Cell Wall

Cell walls vary in composition. We will only discuss bacteria cell wall.

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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.



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



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



CytoplasmCytoplasm is the watery medium where all the molecules

dissolved

Eukaryotic cell



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 !



A Cell Is a Busy Place!



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



Cytokeletal Fibers Are Madeof Building Blocks



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.



Genomes and Nucleus



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



Prokaryote Eukaryote

Additionalplasmids may be present

+ histones

NO histones

P k t l



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



Nucleus & nucleolusHouse DNASite of transcriptionNucleolus: make ribosomes

The cell ’

s hard drive

Eukaryotic cells have amembrane-bound nucleus

Eukaryotic DNA packaging



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:



The Endomembrane System:Involved in the Synthesis Delivery of

Molecules Endoplasmic reticulumGolgi apparatus

Exocityc vesciclesLysosmesEndosomes



The Endomembrane System:



Endocytosis and Exocytosis



https://www.youtube.com/w

atch?v=DuDmvlbpjHQ

E d l i R ti l (ER)

https://www.youtube.com/watch?v=DuDmvlbpjHQ






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.



Exocytosis: Secreting Molecules

How Do the Vescicles Know



How Do the Vescicles KnowWhere to Go?

Cytoskeleton!!!!

vescicle trafficking cartoon via youtube

vescicle trafficking in vitro via youtube

f

http://www.youtube.com/watch?v=7sRZy9PgPvg

http://www.youtube.com/watch?v=4sEyUBoWBt4

http://www.youtube.com/watch?v=4sEyUBoWBt4

http://www.youtube.com/watch?v=7sRZy9PgPvg



Endocytosis: Uptake of Molecules and Cells

Lysosomes



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



, 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



PhagocytesEndocytosis is used by a family of immune

cells known as phagocytes that employ thismechanism to destroy pathogens



http://www.youtube.com/watch?v=Z_mXDvZQ6dU

Amoeba’s Dinner

http://www.youtube.com/watch?v=aWItglvTiLc







http://www.youtube.com/wat

ch?v=aWItglvTiLc

Neutrophil Fights Bacteria

Ribosomes and Protein







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



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



Protein Synthesis andTransport in Eukaryotes



Mitochondria and Chloroplasts

Plants

All eukaryotic cells,including plants

Photosynthesis

Aerobic Respiration





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



https://www.youtube.com/watch?v=wJyUtbn0O5Y

Cell Replication (Telomeres, Biology)

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