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8/3/2019 Lec 2_Attributes of the Cell
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
General Attributes of the Cell
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Overview: The Importance of Cells
• All organisms are made of cells
• The cell is the simplest collection of matter
that can live• Cell structure is correlated to cellular function
• All cells are related by their descent from earliercells
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Size range of cells
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Prokaryotes vs Eukaryotes
• domains Bacteria and Archaea – prokaryotic cells
• domain Eukarya (protists, fungi, animals, andplants) – eukaryotic cells
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• Basic features of all cells:
– Plasma membrane
– Semifluid substance called the cytosol
– Chromosomes (carry genes)
– Ribosomes (make proteins)
Prokaryotes vs Eukaryotes
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• Prokaryotic cells have no nucleus
• In a prokaryotic cell, DNA is in an unbound regioncalled the nucleoid
• Prokaryotic cells lack membrane-bound organelles
Prokaryotes vs Eukaryotes
8/3/2019 Lec 2_Attributes of the Cell
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
A typicalrod-shapedbacterium
A thin section through thebacterium Bacillus coagulans (TEM)
0.5 µm
Pili
Nucleoid
Ribosomes
Plasma
membrane
Cell wall
Capsule
Flagella
Bacterialchromosome
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
ANIMAL CELL TYPES
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
PLANT CELL TYPES
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• selective barrier that allows passage ofoxygen, nutrients, and wastes for the whole
volume of the cell
Cell Parts: Plasma membrane
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• contains most of the DNA in a eukaryotic cell
Cell Parts: Nucleus
Close-up of nuclearenvelope
Nucleus
Nucleolus
Chromatin
Nuclear envelope:Inner membraneOuter membrane
Nuclear pore
Porecomplex
Ribosome
Pore complexes (TEM) Nuclear lamina (TEM)
1 µm
Rough ER
Nucleus1 µm
0.25 µm
Surface of nuclear envelope
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• particles made of ribosomal RNA and protein
• carry out protein synthesis in two locations:
– cytosol (free ribosomes)
– outside of the endoplasmic reticulum (ER) orthe nuclear envelope (bound ribosomes)
Cell Parts: RibosomesRibosomes
0.5 µm
ER Cytosol
Endoplasmicreticulum (ER)Free ribosomes
Bound ribosomes
Largesubunit
Smallsubunit
Diagram of
a ribosome
TEM showing ER
and ribosomes
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• Components : – Nuclear envelope
– Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane
• These components are either continuous orconnected via transfer by vesicles
Cell Parts: Endomembrane system
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• accounts for more than half of the total membranein many eukaryotic cells
• continuous with the nuclear envelope
• two distinct regions of ER:
– Smooth ER
– Rough ER
Cell Parts: Endoplasmic Reticulum
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Ribosomes
Smooth ER
Rough ER
ER lumen
Cisternae
Transport vesicle
Smooth ER Rough ER
Transitional ER
200 nm
Nuclearenvelope
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Functions of Smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Stores calcium
– Detoxifies poison
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
– produces proteins and membranes, which aredistributed by transport vesicles
– membrane factory for the cell
Functions of Rough ER
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• consists of flattened membranous sacs calledcisternae
• Functions:
– modifies products of the ER
– manufactures certain macromolecules
– sorts and packages materials into transportvesicles
Cell Parts: Golgi apparatus
trans face(“shipping” side of Golgi apparatus) TEM of Golgi apparatus
0.1 µm
Golgiapparatus
cis face(“receiving” side of Golgi apparatus)
Vesicles coalesce toform new cis Golgi cisternaeVesicles also
transport certainproteins back to ER
Vesicles movefrom ER to Golgi
Vesicles transport specificproteins backward to newerGolgi cisternae
Cisternalmaturation:Golgi cisternaemove in a cis -to- trans direction
Vesicles form andleave Golgi, car ryingspecific proteins toother locations or tothe plasma mem-brane for secretion
Cisternae
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• membranous sac of hydrolytic enzymes
• enzymes can hydrolyze proteins, fats,polysaccharides, and nucleic acids
• use enzymes to recycle organelles andmacromolecules, a process called autophagy
Cell Parts: Lysosomes
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Phagocytosis: lysosome digesting food
1 µm
Plasmamembrane
Food vacuole
Lysosome
Nucleus
Digestiveenzymes
Digestion
Lysosome
Lysosome containsactive hydrolyticenzymes
Food vacuolefuses withlysosome
Hydrolyticenzymes digestfood particles
Autophagy: lysosome breaking downdamaged organelle
1 µm
Vesicle containingdamaged mitochondrion
Mitochondrionfragment
Lysosome containingtwo damaged organelles
Digestion
Lysosome
Lysosome fuses withvesicle containingdamaged organelle
Peroxisomefragment
Hydrolytic enzymesdigest organellecomponents
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• vesicles and vacuoles are membrane-bound sacswith varied functions
• a plant cell or fungal cell may have one or severalvacuoles
Cell Parts: Vacuoles
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• food vacuoles are formed by phagocytosis
• contractile vacuoles , found in many freshwaterprotists, pump excess water out of cells
• central vacuoles , found in many mature plantcells, hold organic compounds and water
Cell Parts: Vacuoles
5 µm
Central vacuole
Cytosol
Tonoplast
Centralvacuole
Nucleus
Cell wall
Chloroplast
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
The Endomembrane System: A Review
• a complex and dynamic player in the cell’scompartmental organization
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Nuclear envelope
Nucleus
Rough ER
Smooth ERNuclear envelope
Nucleus
Rough ER
Smooth ER
Transport vesicle
cis Golgi
trans Golgi
Nuclear envelope
Nucleus
Rough ER
Smooth ER
Transport vesicle
cis Golgi
trans Golgi
Plasmamembrane
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Mitochondria and chloroplasts change energyfrom one form to another
• mitochondria are the sites of cellular respiration
• chloroplasts , found only in plants and algae, arethe sites of photosynthesis
• mitochondria and chloroplasts are not part of theendomembrane system
• peroxisomes are oxidative organelles
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• are in nearly all eukaryotic cells
• with smooth outer membrane and an inner
membrane folded into cristae• inner membrane creates two compartments:
intermembrane space and mitochondrial matrix
Cell Parts: MitochondriaMitochondrion
Intermembrane space
Outermembrane
Innermembrane
Cristae
Matrix
100 nmMitochondrialDNA
Freeribosomesin themitochondrialmatrix
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• member of a family of organelles called plastids
• contain chlorophyll, as well as enzymes and othermolecules that function in photosynthesis
• found in leaves and other green organs of plantsand in algae
• structure includes: – thylakoids, membranous sacs – stroma, the internal fluid
Cell Parts: Chloroplasts
Chloroplast
ChloroplastDNA
RibosomesStroma
Inner and outermembranes
Granum
Thylakoid1 µm
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• specialized metabolic compartments bounded bya single membrane
• produce hydrogen peroxide and convert it to water
Cell Parts: Peroxisomes
Chloroplast
Peroxisome
Mitochondrion
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• a network of fibers extending throughout thecytoplasm
• organizes the cell’s structures and activities,anchoring many organelles
• composed of three types of molecular structures: – microtubules – microfilaments
– intermediate filaments
Cell Parts: Cytoskeleton
Microtubule
Microfilaments0.25 µm
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Roles of the Cytoskeleton
• helps to support the cell and maintain its shape
• interacts with motor proteins to produce motility
• vesicles can travel along “monorails” provided bythe cytoskeleton
• may help regulate biochemical activities
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Vesicle
Receptor for
motor protein
Microtubuleof cytoskeleton
Motor protein(ATP powered)
ATP
0.25 µmMicrotubule Vesicles
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Components of the Cytoskeleton
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Components of the Cytoskeleton
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Components of the Cytoskeleton
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Centrosomes and Centrioles
• In many cells, microtubules grow out from acentrosome near the nucleus
• The centrosome is a “microtubule -organizingcenter”
• In animal cells, the centrosome has a pair ofcentrioles, each with nine triplets of microtubulesarranged in a ring
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
0.25 µm
Microtubule
Centrosome
Centrioles
Longitudinal sectionof one centriole
Microtubules Cross sectionof the other centriole
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Cilia and Flagella
• Microtubules control the beating of cilia andflagella, locomotor appendages of some cells
• Cilia and flagella differ in their beating patterns
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
5 µm
Direction of swimming
(a) Motion of flagella
Direction of organism’s movement
Power stroke Recovery stroke
(b) Motion of cilia15 µm
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• Cilia and flagella share a common ultrastructure:
– a core of microtubules sheathed by the plasmamembrane
– a basal body that anchors the cilium orflagellum
– a motor protein called dynein, which drives thebending movements of a cilium or flagellum
0.5 µm
Microtubules
PlasmamembraneBasal body
Plasmamembrane
0.1 µm
Cross section of basal body
Triplet
Outer microtubuledoublet
0.1 µm
Dynein armsCentralmicrotubuleCross-linkingproteins insideouter doublets
Radialspoke
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
• How dynein “walking” moves flagella and cilia: – Dynein arms alternately grab, move, and
release the outer microtubules – Protein cross-links limit sliding – Forces exerted by dynein arms cause doublets
to curve, bending the cilium or flagellum
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Dynein “walking”
Microtubuledoublets ATP
Dynein arm
LE 6-25b
Wavelike motion
Cross-linkingproteins insideouter doublets
ATP
Anchoragein cell
Effect of cross-linking proteins
Microfilaments (actinfilaments)
Microvillus
Plasma membrane
Intermediate filaments
0.25 µm
• form a 3Dnetwork justinside theplasmamembrane tohelp support thecell’s shape
• bundles ofmicrofilamentsmake up thecore of microvilliof intestinal cells
Microfilaments(Actin filaments)
Muscle cell
Actin filament
Myosin filamentMyosin arm
Myosin motors in muscle cell contraction
• microfilaments that function in cellular motility contain theprotein myosin in addition to actin
Cortex (outer cytoplasm):gel with actin network
Amoeboid movement
Inner cytoplasm: solwith actin subunits
Extendingpseudopodium
• localized contraction brought about by actin and myosinalso drives amoeboid movement
• pseudopodia (cellular extensions) extend and contractthrough the reversible assembly and contraction of actinsubunits into microfilaments
Nonmovingcytoplasm (gel)
Cytoplasmic streaming in plant cells
Chloroplast
Streamingcytoplasm(sol)
Cell wallParallel actinfilaments
Vacuole
• actin-myosin interactions and sol-gel transformations drivecytoplasmic streaming
• speeds distribution of materials within the cell
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Intermediatefilaments
• support cellshape and fixorganelles inplace
• are morepermanentcytoskeletonfixtures thanthe other twoclasses
Microvillus
Plasma membrane
Microfilaments (actinfilaments)
Intermediate filaments
0.25 µmCopyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Extracellular components
• materials that are external to the plasmamembrane
• synthesized and secreted by most cells• include:
– cell walls of plants
– extracellular matrix (ECM) of animal cells
– intercellular junctions
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Cell Walls of Plants
• protects the plant cell, maintains its shape, andprevents excessive uptake of water
• made of cellulose fibers embedded in otherpolysaccharides and protein
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Cell Walls of Plants
• may have multiple layers:
– primary cell wall : relatively thin and flexible
– middle lamella : thin layer between primarywalls of adjacent cells
– secondary cell wall (in some cells): addedbetween the plasma membrane and theprimary cell wall
• plasmodesmata are channels between adjacentplant cells
Centralvacuoleof cell
PlasmamembraneSecondarycell wall
Primarycell wall
Middlelamella
1 µm
Central
vacuoleof cell
Central vacuoleCytosol
Plasma membrane
Plant cell walls
Plasmodesmata
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
The Extracellular Matrix (ECM) of Animal Cells
• animal cells lack cell walls but are covered by anelaborate extracellular matrix (ECM)
• made up of glycoproteins and othermacromolecules
• Functions of the ECM: – support – adhesion – movement – regulation
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
EXTRACELLULAR FLUID ProteoglycancomplexCollagen
fiber
Fibronectin
Integrin Micro-filaments
CYTOPLASM
Plasmamembrane
Polysaccharidemolecule
Carbo-hydrates
Coreprotein
Proteoglycanmolecule
Proteoglycancomplex
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Intercellular Junctions
• neighboring cells in tissues, organs, or organsystems often adhere, interact, and communicatethrough direct physical contact
• intercellular junctions facilitate this contact
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Plants: Plasmodesmata
• channels that perforate plant cell walls
• for passage of water and small solutes (andsometimes proteins and RNA) from cell to cell
Interiorof cell
Interiorof cell
0.5 µm Plasmodesmata Plasma membranes
Cell walls
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
Animals: Tight Junctions, Desmosomes,and Gap Junctions
• at tight junctions , membranes of neighboring cellsare pressed together, preventing leakage of
extracellular f luid• desmosomes (anchoring junctions) fasten cells
together into strong sheets
• gap junctions (communicating junctions) providecytoplasmic channels between adjacent cells
Tight junctions preventfluid from movingacross a layer of cells
Tight junction
0.5 µm
1 µm
0.1 µm
Gap junctionExtracellularmatrix
Spacebetweencells
Plasma membranesof adjacent cells
Intermediatefilaments
Tight junction
Desmosome
Gapjunctions
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ology 11 Lecture 2 JPQ/TLS/LBU//CCB/JJMP
Copyright © 2005 Pearson Education, Inc. publishingas Benjamin Cummings
The Cell: A Living Unit Greater Than the Sum of Its Parts
• cells rely on the integration of structures andorganelles in order to function
• for example, a macrophage’s ability to destroybacteria involves the whole cell, coordinatingcomponents such as the cytoskeleton, lysosomes,and plasma membrane
5 µ m
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