CELLS: UNITS OF LIFE
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Transcript of CELLS: UNITS OF LIFE
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Chapter 4Hyperlink is the 3rd one that says
component of cells – same as above, but narrated!
CELLS: UNITS OF LIFE
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The Discovery of CellsAll organisms consist of cells
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The Discovery of CellsCells – the place where
biochemical activity occurs
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The Discovery of CellsCells – have ALL characteristics of
lifeAll made of cells – and have levels of organization
All grow, develop, and reproduceAll use energyAll adaptAll respond to stimuliMaintain internal constancy
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The Discovery of CellsCells – cell membrane –
separates living matter from the environment and limits size of organism
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The Discovery of CellsOrganelles – structures where
life processes occur to keep cell alive
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The Discovery of CellsCellular Cytoplasm- remainder of
interior of cell besides organelles
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The Discovery of CellsCells can specialize (examples :
muscle cells, leaf cells, root cells)
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The Discovery of CellsStem cells –
from which all cells differentiate in many celled organism
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Lenses Reveal the World of the Cell13th Century – world
recognized glass magnifies
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Lenses Reveal the World of the Cell16th Century – began using paired
lenses (Jansen and church spire)
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Lenses Reveal the World of the Cell• Robert Hooke (1660)
• 1st person to see the outlines of cells• Spun glass and looked at bee stingers, fish scales, fly
legs, insects and CORK• Antonie van Leeuwenhoek (1673)
• developed over 500 high magnification lenses• 1st record of microorganisms- he called
“animalcules” found in tooth tartar
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The Cell Theory Emerges – not till 19th Century Robert Brown – discovered
cellular nucleus Houses DNA
Schleiden Cells were basic unit of
plants Schwann
Cells were basic unit of animals
Together Cells were elementary
particles of all organisms, the unit of structure and function
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VirchowAll cells come
from pre-existing cells
Believed abnormal cells cause diseases
The Cell Theory Emerges – not till 19th Century
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Cell Theory1. All living things are composed
of cells. [Schleiden & Schwann]
2. All cells come from preexisting cells. [Virchow]
Cell Theory still evolving: Organelles have precise locations
in cells
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C. Types of Cells3 basic types:• Bacterial• Archaean
Prokaryotic
• Eukaryotic
Variations on the Cellular Theme
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Review surface area to volume relationship – Large volume justifies the need to have organelles
Variations on the Cellular Theme
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Variations on the Cellular ThemeFolding membranes also increase surface
area for reactions
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1. Bacterial cells • 1-10 m in diameter • NO membrane-bound organelles• Some photosynthetic – use pigment only• Some cause illness some don’t• Vital to life on earth• 1 circular DNA molecule located in nucleoid region
• MAKE PROTEINS RAPIDLY DUE TO CLOSE LOCATION OF ORGANELLS
• plasma membrane, cytoplasm & ribosomes• most have a cell wall (peptidoglycan)
• Many antibiotics interfere with cell wall construction
• may have a polysaccharide capsule to protect or attach
• Film on teethn morningEx. bacteria & cyanobacteria
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Bacterial ShapesCocciBacilliSpirillaFibrios fusiform
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Gram-stainingDistinguishes 2 types of bacteria •Gram – negative – thin cell wall•Gram positive – thick cell wall
Structure of a Gram-Negative Cell Wall Gram positive cell wall
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Archaean cells represent a distant ancestor???• 1-10 m in diameter• Use carbon dioxide and
hydrogen to make methane (methanogens)
• Have co-enzymes that make methane
• NO membrane-bound organelles• cell walls lack peptidoglycan• have characteristics of both
bacteria & eukaryotic cells• Half of genes are same as
bacteria, other half totally different
• mRNA and tRNA are different than in other domains
Methanogen
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Archaean Extremophiles, con’t
Ex. Extremophiles: extreme environments: temp, pressure, pH, salinity
methanogens, extreme halophiles & extreme thermophiles
Live in Swamps, rice paddies and oceans
Extreme halophile
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3. Eukaryotic cells• 10-100 m in diameter • Includes plants, animals, fungi and protists• nucleus & other membrane-bound organelles• Nucleus
• Protects and organizes the cell’s linear DNA• DNA combined with protein forming chromosomes
• plasma membrane, cytoplasm & ribosomes• some have a cell wall (cellulose or chitin) • Animal cells: half the volume of a cell is organelles• Plant cells: 90% may be water (found in vacuole)• Cytoskeleton – rods and tubules within cells to give
cell shape or appendages to move
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Introduction to Organelles Organelles –
improve efficiency, protect contents, secrete substances, derive energyDegrade debrisreproduce
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Introduction to Organelles Organelles Synthesize and Process Proteins
Enzymes – key to determining function of cell
Endomembrane system Rough endoplasmic reticulum
Compartments use enzymes that assist with protein production and transportation
Smooth endoplasmic reticulumLipids synthesized, modified and
toxins neurtalized
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Generalized Generalized Animal Cell Plant Cell
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Introduction to Organelles’s cont Golgi apparatus
Sorts proteins for exports out of cell or into lysosomes
links simple carbohydrates together to form starch
links simple carbohydrates to proteins (glycoprotein) or lipids (glycolipid)
completes folding of proteins temporarily stores secretions
(milk)
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Organelle interaction in a mammary gland cell.
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Introduction to Organelles’s cont Lysosomes (suicide sacs)
Contain digestive enzymes – 40 types Function to recycle damaged organelles,
break down cellular by products & destroy invading microbes
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The Nucleus Exports RNA instructions
Genes: instructions on DNA are copied onto mRNA
mRNA exits nucleus through nuclear pores (found in nuclear envelope Not just holes Channels with 100 types of proteins
(importins and exportins)
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The Cytoplasm Site of Protein synthesis and other
reactions mRNA binds to ribosomes
A complex of MANY proteins surrounding an rRNA
rRNA + proteins are assembled in the nucleolus then exit the nucleus through pores
Remainder of section completes milk production example
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Lysosomes and Peroxisomes: Cellular Digestion Centers – and more
Lysosomes are cellular recycling centers Lyse – cut apart Enzymes within organelle – lyse targets
Dismantle bacteria Dismantle worn out organelles and debris Break down large nutrients into useable
monomers Fuse with vesicles carrying debris Made in rough ER Function in very acidic environment
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Lysosome’s con’t Numbers very based on cell function
White blood cells have many Liver have MANY – process cholesterol
Human cells have more than 40 enzyme types
Balance of enzyme related to health Too many, causes storeage problems in
cell – crowds other organelles Tay Sachs – missing an enzyme in a
lysosome
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Tay Sachs events
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PeroxisomesFacilitate oxidative Reactions
Contain enzymes that oxidize other molecules
Enzymes made in the cytoplasm – then transported to vesicles
Environmental toxins: cause explosion of peroxisome production Toxins are oxidized and removed
Synthesize bile acids
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Peroxisomes, con’t Break down lipids Degrade rare biochemicals Metabolize free radicals Some produce hydrogen peroxide
Produces free radicals So contain catalase – removes oxygen
from hydrogen peroxide to make water Found in leaves Adrenoleukodystrophy (Lorenzo’s disease) –
two proteins missing in peroxisomes outer membrane pg 59
Leopard spot retinal pigmentation
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Mitochondria – organelle of energy Mitochondria Extract Energy from
nutrientsNumbers vary from few to 1000’sCristae – inner folds contain
enzymesSite of cellular respiration (ATP)
Converts glucose into ATP energy
Has own genetic material (DNA) Inherited only from female
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Chloroplast – organelle of energy Chloroplasts provide plant cells with nutrients
(THEREFORE ENERGY) Chloroplast
carry out photosynthesis Form glucose or other carbohydrates Have stroma – space inside chloroplast for
reactions Thylakoids – membrane system of stacked
sacks called grana where reactions take place Has own DNA See Table pg 60
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Origin of Complex Cells Endosymbiont theory – large celled critters
engulfed smaller simpler cells. Simple cells became organelles in the larger critter Structure and DNA sequences provide
evidence Evidence in FAVOR of EST
Resemblance between mitochondria and chloroplasts to certain kinds of bacteria
» Size» Shape» Membrane structure» Presence of pigments» Reproduction method» Relative relationship of DNA, RNA and ribosomes
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Origins of Complex Cells, con’t Technology Evidence DNA evidence – bacteria and archaea
contributed Theory: archaean cells enveloped
bacterial cells that became mitochondria and chloroplasts
Theory: bacteria share genes with bacteria and vice versa
Ricettsia
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Endosymbiant Theory
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Origins of Complex Cells, cont
How Endosymbiosis May have worked, pg 61
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2. Endoplasmic reticulum (ER)• interconnected network of membranes extending from nucleus to plasma membrane
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3. Golgi apparatus • stacks of membrane-enclosed
sacs
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4. Lysosomes (suicide sacs)• vesicles containing > 40 types of
digestive enzymes
• function to recycle damaged organelles, break down cellular byproducts & destroy invading microbes
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5. Perixisomes• vesicles containing several types
of enzymes (produced in cytoplasm)• found in all eukaryotic cells• function to help cell use oxygen
& metabolize potentially toxic compounds
• hydrogen peroxide is produced as a by-product of peroxisome activity
• the enzyme catalase converts hydrogen peroxide to water
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• #/cell varies• contain DNA• inherited from female parent• site of cellular respiration
(production of ATP)
6. Mitochondria• double-
membrane• outer is smooth• inner is highly
folded (cristae)
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7. Chloroplasts• possess 3 membranes
• outer/inner membranes surround stroma• 3rd membrane system folded into flattened
sacs (thylakoids)
• #/cell varies • contain DNA• found in plants & protists• function in
photosynthesis
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E. The Endosymbiont TheoryProposes that chloroplasts and
mitochondria evolved from once free-living bacteria engulfed by larger archaea.
Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure & method of making proteins).
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