a tour of the cell ch. 4 engineering 2 ms. haut. introduction to the world of the cell the...
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Principles of the Cell Theory 1.All living things are made of one or more cells 2.Cells are the basic unit of structure & function in organisms 3.Cells come only from the reproduction of existing cellsTRANSCRIPT
A Tour of the Cell
Ch. 4Engineering 2
Ms. Haut
INTRODUCTION TO THE WORLD OF THE CELL
• The microscope was invented in the 17th century
• Using a microscope, Robert Hooke discovered cells in 1665
• All living things are made of cells (cell theory) http://www.edu365.com/aulanet/comsoc/
persones_tecniques/Robert_Hooke_archivos/Robert_Hooke.jpg
Principles of the Cell Theory
1. All living things are made of one or more cells
2. Cells are the basic unit of structure & function in organisms
3. Cells come only from the reproduction of existing cells
Microscopes provide windows to the world of the cell
• The light microscope enables us to see the overall shape and structure of a cell
Figure 4.1A
Image seen by viewer
Eyepiece
Ocularlens
Objective lensSpecimenCondenser lens
Light source
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Red blood cellsteaching.path.cam.ac.uk/partIB_pract/NHP1/
Electron microscopes
• Invented in the 1950s• They use a beam of
electrons instead of light
• The greater resolving power of electron microscopes – allows greater
magnification – reveals cellular details
websemserver.materials.ox.ac.uk/cybersem/getf...
Scanning electron microscope (SEM)
• Used to see detailed structure of cell surface
Figure 4.1B
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Red blood cellshttp://commons.wikimedia.org/wiki/Image:SEM_blood_cells.jpg
Transmission electron microscope (TEM)
• Used to examine the internal structures of a cell
Figure 4.1CCopyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Red blood cell in capillarycommons.wikimedia.org/wiki/Image:A_red_blood_...
• Cell size and shape relate to function
Figure 4.2
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
• At minimum, a cell must be large enough to house the parts it needs to survive and reproduce
• The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes
Natural laws limit cell size
• A small cell has a greater ratio of surface area to volume than a large cell of the same shape
30 µm 10 µm
Surface areaof one large cube= 5,400 µm2
Total surface areaof 27 small cubes= 16,200 µm2Figure 4.3
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Categories of Cells
•Contains membranous organelles
•No membranous organelles
•DNA in a membrane bound nucleus
•DNA in nucleoid region (no nucleus)
•More complex structure•Simpler structure
•Larger size•Smaller size
EukaryoticProkaryotic
• Enclosed by a plasma membrane
• Usually encased in a rigid cell wall – The cell wall may be
covered by a sticky capsule
• Inside the cell are its DNA and other parts
Ribosomes
Figure 4.4
CapsuleCell wall
Plasmamembrane
Prokaryoticflagella
Nucleoid region(DNA)Pili
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Prokaryotes
• All other life forms are made up of one or more eukaryotic cells
• These are larger and more complex than prokaryotic cells
• Eukaryotes are distinguished by the presence of a true nucleus
Eukaryotic cells are partitioned into functional compartments
• An animal cell
Plasma membrane
Figure 4.5A
Golgiapparatus
Ribosomes
NucleusSmooth endoplasmicreticulum
Roughendoplasmicreticulum
Mitochondrion
Not in most plant cells
Cytoskeleton
Flagellum
Lysosome
Centriole
Peroxisome
Microtubule
Intermediatefilament
Microfilament
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The Plasma Membrane:A Fluid Mosaic of Lipids and Proteins
• The membranes of cells are composed of:
• Phospholipids• Proteins• Cholesterol
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http://bio.winona.edu/berg/ILLUST/memb-mod.jpg
Plasma Membrane
• Phospholipids form a two-layered membrane, the phospholipid bilayer.
Figure 4.7a
Figure 4.7b
Plasma Membrane
• Most membranes have specific proteins embedded in the phospholipid bilayer.
• Proteins serve a number of functions• Transport channels• Enzymes
Plasma Membrane
• Cholesterol molecules help keep the membrane “fluid” at lower temperatures
http://www.uic.edu/classes/bios/bios100/lectf03am/cholesterol.jpg
http://sps.k12.ar.us/massengale/images/cell20membrane.jpg
Cholesterol
Fluid Mosaic Model
• Fluid part of model:• Membrane phospholipids and proteins can
drift about in the plane of the membrane.• Mosaic part of model:
• A diversity of molecules exists within the membrane
• Phospholipids• Different proteins• Cholesterol
Membranes• The plasma membrane
separates the living cell from its nonliving surroundings.
• The cytoplasm contains organelles
• Most organelles have membranes– These compartmentalize
the interior of the cell– This allows the cell to carry
out a variety of activities simultaneously
Plant Cells
• A plant cell has some structures that an animal cell lacks:– Chloroplasts – A rigid cell wall– Central vacuole– Plasmodesmata
• The largest organelle is usually the nucleus• The nucleus is separated from the cytoplasm
by the nuclear envelope• The nucleus is the cellular control center
– It contains the DNA that directs the cell’s activities
The nucleus is the cell’s genetic control center
Nucleus
Figure 4.6
Chromatin
Nucleolus
Pore
NUCLEUS
Two membranesof nuclearenvelope
ROUGHENDOPLASMICRETICULUM
Ribosomes
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Many cell organelles are related through the endomembrane system
• The endomembrane system is a collection of membranous organelles– Organelles
manufacture and distribute cell products
– Divides cell into compartments
Rough endoplasmic reticulum• The rough ER manufactures membranes• Ribosomes on its surface are sites where
proteins are made
1 2
3
4Transport vesiclebuds off
Ribosome
Sugarchain
Glycoprotein
Secretory(glyco-) proteininside transportvesicle
ROUGH ER
PolypeptideFigure 4.8
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http://micro.magnet.fsu.edu/cells/endoplasmicreticulum/images/endoplasmicreticulumfigure1.jpg
Smooth endoplasmic reticulum has a variety of functions
• Smooth ER synthesizes lipids
• In some cells, it regulates carbohydrate metabolism and breaks down toxins and drugs
SMOOTH ER
ROUGHER
Nuclearenvelope
Ribosomes
SMOOTH ER ROUGH ER
Figure 4.9
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Golgi apparatus
• The Golgi apparatus consists of stacks of membranous sacs – These receive and modify ER products, then send
them on to other organelles or to the cell membrane
Figure 4.12
• A membrane-enclosed sac budded off the Golgi– It contains digestive
enzymes.– The enzymes break
down macromolecules
Lysosomes digest the cell’s food and wastes
LYSOSOME
Nucleus
Figure 4.11A
Lysosomal enzymes
• digest food• destroy bacteria• recycle damaged
organelles• function in embryonic
development in animals
http://sun.menloschool.org/~cweaver/cells/e/lysosomes/lysozome.jpg
Peroxisomes
• Specialized lysosome containing catalase
• Produces hydrogen peroxide (H2O2) as waste product
• Catalase breaks down toxic H2O2
H2O2 ---catalase---> H2O + O2
http://faculty.une.edu/com/abell/histo/peroxisome.jpg
• Plant cells contain a large central vacuole– The vacuole
has lysosomal and storage functions
Vacuoles function in the general maintenance of the cell
Centralvacuole
Nucleus
Figure 4.13A
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Contractile Vacuole
• Protists may have contractile vacuoles– These pump out
excess water
Figure 4.13B
Nucleus
Contractilevacuoles
Copyright © 2003 Pearson Education, Inc. publishing Benjamin CummingsCollapsing contractile vacuole of Protozoawww.microscopy-uk.org.uk/.../vidjuna.html
• The various organelles of the endomembrane system are interconnected structurally and functionally
A review of the endomembrane system
Transport vesiclefrom ER
Rough ER
Transport vesiclefrom Golgi
Plasmamembrane
Vacuole
LysosomeGolgiapparatusNuclear
envelopeSmooth ER
Nucleus
Figure 4.14Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
ENERGY-CONVERTING ORGANELLES
• Chloroplasts• Mitochondria
Chloroplasts
• Chloroplasts are found in plants and some protists
• Chloroplasts convert solar energy to chemical energy in sugars
Figure 4.16
Mitochondria
• Mitochondria carry out cellular respiration– This process uses the chemical energy
in food to make ATP for cellular work
Figure 4.17
Endosymbiosis– Mitochondria and chloroplasts each contain their own
DNA separate from the nucleus.– Evidence for Endosymbiosis theory
• Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past.
http://faculty.ircc.edu/faculty/tfischer/images/endosymbiosis.jpg
• A network of protein fibers makes up the cytoskeleton
The cell’s internal skeleton helps organize its structure and activities
THE CYTOSKELETON AND RELATED STRUCTURES
Figure 4.17A
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• Microfilaments of actin enable cells to change shape and move
• Intermediate filaments reinforce the cell and anchor certain organelles
• Microtubules – give the cell rigidity– provide anchors for organelles– act as tracks for organelle movement
3 Types of fibers make up the cytoskeleton
Figure 4.17B
MICROFILAMENT INTERMEDIATEFILAMENT
MICROTUBULE
Actin subunit Fibrous subunitsTubulinsubunit
7 nm 10 nm25 nm
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Cilia and flagella move when microtubules bend
• Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells
• A cilia or flagellum is composed of a core of microtubules wrapped in an extension of the plasma membrane
www.cco.caltech.edu/~brokawc/Demo1/BeadExpt.html
http://fig.cox.miami.edu/~cmallery/150/cells/centriole.jpg
http://www.microscopy-uk.org.uk/mag/imgjan99/janvid2.gif
• Cells interact with their environments and each other through their surfaces
• Plant cells are supported by rigid cell walls made largely of cellulose– They connect by plasmodesmata, channels that
allow them to share water, food, and chemical messages
Cell surfaces protect, support, and join cells
EUKARYOTIC CELL SURFACES AND JUNCTIONS
Figure 4.19A
Vacuole
Layers of one plant cell wall
Walls of two adjacent plant cells
PLASMODESMATA
Cytoplasm
Plasma membrane
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Animal cells are embedded in an extracellular matrix
• It is a sticky layer of glycoproteins
• It binds cells together in tissues
• It can also have protective and supportive functions
http://kentsimmons.uwinnipeg.ca/cm1504/Image122.gif
• Tight junctions can bind cells together into leakproof sheets
• Anchoring junctions link animal cells
• Communicating junctions allow substances to flow from cell to cell
TIGHTJUNCTION
ANCHORING JUNCTION
COMMUNICATINGJUNCTION
Plasma membranes ofadjacent cells
ExtracellularmatrixFigure 4.19B
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Acknowledgements• Essential Biology with Physiology, 2nd ed., by Campbell, Reece, and
Simon, ©2007. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
• BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
• Background image found at http://www.paxcam.com/imgs/library/2/thumbnails/slide_19.jpg