Chapter 06 A Tour of the Cell
Transcript of Chapter 06 A Tour of the Cell
A Tour of the Cell
Chapter 6
The Cell
Learning Objectives
• Describe principles that limit cell size • Describe fundamental differences between prokaryotic and eukaryotic cell types
• Ability to recognize models of eukaryotic cellular compartments and ascribe functions to each
• Describe essential similarities and difference between animal and plant cells
• Outline intracellular and extracellular protein structures and describe their functions.
2Chapter 6
The Cell 3Chapter 6
Cell Theory
A unifying concept in biologyOriginated from the work of biologists Schleiden and Schwann in 1838-9
States that:All organisms are composed of cells
German botanist Matthais Schleiden in 1838 German zoologist Theodor Schwann in 1839
All cells come only from preexisting cells German physician Rudolph Virchow in 1850’s
Smallest unit of life
The Cell 4Chapter 6
Organisms and Cells
Pallisade cells Squamous epithelial and striated muscle
400X 400X
The Cell 5Chapter 6
Sizes of Living Things
In your notes:• Plant and animal cells have an average size of 50 um• Bacterial cells are roughly 10 smaller with an average size of 2-5
um• Virus particles are approx. 100 times smaller than bacterial and
have an average size of 20-50 nm
The Cell 6Chapter 6
Cell Size
Size restricted by Surface/Volume (S/V) ratioSurface is membrane, across which cell acquires nutrients and expels wastes
Volume is living cytoplasm, which demands nutrients and produces wastes
As cell grows, volume increases faster than surface
Cells specialized in absorption modified to greatly increase surface area per unit volumeIn your notes:
• The cell membrane is like the lungs and intestines of a cell. Therefore the total surface area of the cell membrane must remain large with respect to the cell contents / volume.
• This will only happen if the cell remains small.
The Cell 7Chapter 6
Surface to Volume Ratio
TotalSurfaceArea6cm2(X4) 24cm2(x4) 96cm2
TotalVolume1cm3(x8) 8cm3(x8) 64cm3
SurfaceArea/Volume6 3 1.5
In your notes: • As the volume of a cube or sphere increases it s total exposed surface
area does not increase proportionally. • Therefore, as cells get larger less surface area is available for gas
exchange and nutrient and waste exchange• For this reason cells must remain small. (active cells are generally less
than 50 um in diameter)
Text:p99
The Cell 8Chapter 6
Know your metric measures!
1 m = 100 cm10-2 m = 1 cm = 10 mm (millimeters)10-3 m = 1 mm = 1000 um (micrometers)10-6 m = 1 um = 1000 nm (nanometers)10-9 m
The Cell 9Chapter 6
Microscopes:
Summary: “There are many different technologies applied to microscopy”
You will need to differentiate between: • Light microscopes• Two types of electron microscopes• A couple of others, such as Phase contrast, Imunoflourescence, video enhanced.
The Cell 10Chapter 6
Different techniques for viewing cells: 1. Compound Light Microscope
Light passed through specimen
Focused by glass lenses
Image formed on human retina
Max magnification about 1000X
Resolves objects separated by 0.2 mm, 1000X better than human eye
The Cell 11Chapter 6
Figure 4Aa
The Cell 12Chapter 6
Light Microscopy (1)
The Cell 13Chapter 6
Electron MicroscopyA. Transmission Electron Microscope
Abbreviated T.E.M.Electrons passed through specimenFocused by magnetic lensesImage formed on fluorescent screen
Similar to TV screen Image is then photographed
Max magnification 1,000,000s XResolves objects separated by 0.00002 mm,
100,000X better than human eye
The Cell 14Chapter 6
Figure 6.4 a
The Cell 15Chapter 6
TEM
The Cell 16Chapter 6
b. Scanning Electron Microscope
Abbreviated S.E.M.Specimen sprayed with thin coat of metal
Electron beam scanned across surface of specimen
Metal emits secondary electronsEmitted electrons focused by magnetic lensesImage formed on fluorescent screen
Similar to TV screen Image is then photographed
The Cell 17Chapter 6
S.E.M.Figure 6.4 b
The Cell 18Chapter 6
S.E.M.
The Cell 19Chapter 6
S.E.M.
The Cell 20Chapter 6Two classes of cells. 1. Prokaryotic cells
Lack a membrane-bound nucleusStructurally simpleTwo of lifes Domains are prokaryotes.
A. Bacteria Three Shapes
Bacillus (rod)Coccus (spherical)Spirilla (spiral)
B. Archaea (“Ancient Bacteria) Live in extreme habitats (High temp., High salt, toxic gas)
The Cell 21Chapter 6
Shapes of Bacterial Cells
In your notes: Bacteria have three general shapes1. Cocci = round. 2. Bacilli = rod shaped. 3. Spirochete = spiral shaped.
The Cell 22Chapter 6
Prokaryotic Cells: Visual SummaryParticles,notorganelles,VerysimilartoeukaryoticButsmaller
Fig. 6.5 p97
The Cell 23Chapter 6Prokaryotic Cells:The Envelope
Cell Envelopes (some have a cell envelope!) Glycocalyx
Layer of polysaccharides outside cell wall May be slimy and easily removed, or Well organized and resistant to removal (capsule)
Cell wall – peptidoyglycans (recall = struct. Carb.) Plasma membrane (all have plasma membrane)
Like in eukaryotes Form internal pouches (mesosomes)
The Cell 24Chapter 6
CytoplasmSemifluid solution within the cell No organelles – only small granules of stored nutrients called inclusion bodies
AppendagesFlagella – Provide motilityFimbriae – small, bristle-like fibers that sprout from the cell surface
Sex pili – rigid tubular structures used to pass DNA from cell to cell
Prokaryotic Cells:Cytoplasm & Appendages
The Cell 25Chapter 6
2. Eukaryotic Cells
Domain EukaryaProtistsFungiPlantsAnimals
Cells are subdivided into specialized compartments
- All other life forms on earth are eukaryotes
The Cell 26Chapter 6Eukaryotic Cells :Organelles
Compartmentalization: Isolates reactions from eachother…..therefore…. Increased efficiency and specialization of reactions Allows eukaryotic cells to be larger than prokaryotic cells Two classes of eukaryotic compartments: 1.Endomembrane system:
Organelles that communicate with one anothervia membrane channelsVia small vesicles: includes Golgi, Endoplasmic reticulum,
Nucleus, lysosomes, transport vessicles2. Energy related organelles
Mitochondria & chloroplastsHave their own DNA and ribosomes
The important advancement of eukaryotes: ** copy to your notes!
The Cell 27Chapter 6
The membrane system of cells consists of a phospholipid bilayer
Fig. 6.6 p98
The Cell 28Chapter 6
Label Diagram!
Integral transmembrane protein
Peripheral (surface) protein
Phospholipid (f)
(e)
(g) (i)
The Cell 29Chapter 6
Origin of Eukaryotic Cells
MesosomesSurround geneticmaterial
In your notes:The endosymbiont hypothesis for the origin of eukaryotes.A prokaryote predecessor is thought to have given rise to eukaryotes via incorporation of other advantageous prokaryotes. Defn:Symbiosis = two or more organisms providing each other with some advantages.
(p. 517 Chap. 25)
The Cell 30Chapter 6
Experimental methods for isolating organelles and determining their functions. • Cell fractionation: the breaking apart of cellular
components• Differential centrifugation: Separation of cell
parts by size and density
Works like spin cycle of washerThe faster the machine spins, the smaller the
parts that settled out
The Cell 31Chapter 6
Animal Cell Anatomy
Notes: Animal cells have• Nuclei• Mitochondria• Golgi bodies• Lysosomes• Endoplasmic reticulum• Centrioles• Microtubules• ribosomes• Others
The Cell 32Chapter 6
Cell division, separation of chromosomes
Cellular protection – digestion of macromolecules from invasive organisms
Lipid synthesis
Processes packages and Secretes cell products
Protein synthesis
CellularrespirationProducesATP
-enzymes:alcoholdeydrogenase
The Cell 33Chapter 6
Plant Cell Anatomy
Notes.Plant cells:(in addition to animal cell compartments have)• Large central vacuole• Chloroplasts• Cell walls (cellulose)• Does not have centrioles
Cell Structure and Function
The Cell 34Chapter 6
FunctionsA. Nucleus
The genetic command center of cell, usually near center
Separated from cytoplasm by nuclear envelopeConsists of double layer of membraneNuclear pores permit exchange between nucleoplasm & cytoplasm
Contains:Chromatin = semi fluid form of DNAChromosomes. Before cells divide, DNA must condense in to chromosomes Nucleolus: production center for rRNA
Produces subunits of ribosomes.
The Cell 35Chapter 6
Anatomy of the Nucleus
Fig. 6.9p103
The Cell 36Chapter 6
B. Ribosomes
Serve in protein synthesisComposed of rRNA
Consists of a large subunit and a small subunit
Subunits made in nucleolusMay be located:
On the endoplasmic reticulum (thereby making it “rough”), or
Free in the cytoplasm, either singly or in groups called polyribosomes
The Cell 37Chapter 6
Anatomy of a Ribosome
The Cell 38Chapter 6
C. Endomembrane System
(Improves efficiency of eukaryotic cells by isolating mechanisms and reactions to specialized compartments)
Consists of:a. Endoplasmic reticulum (both smooth and rough)
b. Golgi apparatusc. Vesicles
Several types Transport materials between organelles of system
The Cell 39Chapter 6
a. The Endoplasmic Reticulum
i. Rough ERStudded with ribosomes on cytoplasmic sideProtein anabolism (building proteins)
Synthesizes proteins Modifies proteins
Adds sugar to proteinResults in glycoproteins
ii. Smooth ERNo ribosomesSynthesis of lipids (triglycerides, steroids, phospholipids)
-modifications occur In golgi apparatus
The Cell 40Chapter 6
Endoplasmic Reticulum
LipidsIn smooth ER
ProteinsIn rough ER
To golgi apparatus
Fig. 6.11 p105
The Cell 41Chapter 6
The Golgi Apparatusb. Golgi Apparatus
Consists of 3-20 flattened, curved sacculesResembles stack of hollow pancakesModifies proteins and lipids
Packages them in vesicles Receives vesicles from ER on cis face Prepares for “shipment” in vesicles from trans faceWithin cellExport from cell (secretion, exocytosis)
Note: Learn to recognize in a cellular cartoon. Remember its function: Packages and modifies proteins and fats for shipment elsewhere inside and outside of the cell.
The Cell 42Chapter 6
Golgi Apparatus
The golgi receives lipids and proteinsFrom the rough and smooth ER; theyAre modified in the Golgi and the shippedEither out of the cell or to other regionsOf the cell
Fig 6.12 p106
The Cell 43Chapter 6The Golgi also constructs Lysosomes
Lysosomes : vessicles containing hydrolytic enzymes that can digestcellular debris (damaged organelles), incoming food particles, phagocytosed foreign cells and viruses.
The Cell 44Chapter 6
c. Lysosomes
Membrane-bound vesicles (not in plants)Produced by the Golgi apparatusLow pHContain lytic enzymes
Digestion of large molecules Recycling of cellular resources Apoptosis (programmed cell death, like tadpole losing tail)
Some genetic diseasesCaused by defect in lysosomal enzymeLysosomal storage diseases (Tay-Sachs)
Notes:
Remember the term “Hydrolysis” ?- lytic- lysis- lysosome……….all these terms have something to
do with enzymatically degrading or taking apart of organic molecules.
Old cells or unspecialized cells have to make way for newer or more specialized cell………getting rid of old cells involves a procecess called APOPTOSIS.
The Cell 45Chapter 6
Endomembrane System: A Visual Summary
Exocytosis: sends materialout (exits) of the cell.
Lysosome Fig 6.15p109
The Cell 46Chapter 6
Getting proteins into the ERSorting:
Fig 17.21 p.352
The Cell 47Chapter 6Plant Cells:A. Peroxisomes
Similar to lysosomesMembrane-bounded vesiclesEnclose enzymes
HoweverEnzymes synthesized by free ribosomes in cytoplasm (instead of ER)
Active in lipid metabolism (break down fats)
Catalyze reactions that produce hydrogen peroxide H2O2 Toxic Broken down to water & O2 by catalase
The Cell 48Chapter 6
PeroxisomesBreaks down fats, oils and proteinsto hydrogen peroxide.More common in plants but also foundin some animal cells (liver).
• Forms a crytaline core structure ofoxidative enzymes• Is not formed from the endomembrane system (self-replic.)
The Cell 49Chapter 6Plants: B. Vacuoles
Membranous sacs that are larger than vesiclesStore materials that occur in excessOthers very specialized (contractile vacuole)
Plants cells typically have a central vacuoleUp to 90% volume of some cellsFunctions in:
Storage of water, nutrients, pigments, and waste products
Development of turgor pressure (ie: plants can be turgid or
flacid)
Some functions performed by lysosomes in other eukaryotes
The Cell 50Chapter 6
Vacuoles
Fig. 6.14, p. 108
The Cell 51Chapter 6Energy-Related Organelles:1. Chloroplasts
Captures light energy to drive cellular machinery
Photosynthesis
Synthesizes carbohydrates from CO2 & H2O
Makes own food using CO2 as only carbon source Autotrophic
The Cell 52Chapter 6
Chloroplast Structure
Bounded by double membraneInner membrane infolded
Forms disc-like thylakoids, which are stacked to form grana
Suspended in semi-fluid stromaGreen due to chlorophyll
Green photosynthetic pigmentFound ONLY in inner membranes of chloroplast
The Cell 53Chapter 6Energy-Related Organelles:Chloroplast Structure
?
Fig. 6.18 p111
The Cell 54Chapter 6Energy-Related Organelles:2. Mitochondria
Bounded by double membrane
Cristae – Infoldings of inner membrane that encloses matrix
Matrix – Inner semifluid containing respiratory enzymes
Involved in cellular respiration
Produce most of ATP utilized by the cell
The Cell 55Chapter 6Energy-Related Organelles:Mitochondrial Structure
Fig. 6.17p111
The Cell 56Chapter 6
The Cytoskeleton
Maintains cell shapeAssists in movement of cell and
organellesThree types of macromolecular fibers
1. Actin Filaments (small)2. Intermediate Filaments (medium)3. Microtubules (bigger)
Assemble and disassemble as needed
The Cell 57Chapter 6The Cytoskeleton:Actin Filament Operation
Functionincellularmovementthroughflowandmovementoftheplasmamembrane.
The Cell 58Chapter 6
Intermediate filamentsBigger – hold shape of organelles – used in cell attachment to other cells.
• Myosin• Dynein• Kinesin
The Cell 59Chapter 6The Cytoskeleton:Microtubule Operation
Alpha and Beta tubulin pairs form hollow cylinders
Can form, unform and reform again. In this way they movechromosomes into the correct positions for cell division. Also form major structural component of flagella
The Cell 60Chapter 6
Moving chromosomes: Mitotic Spindle
metaphase
anaphase
telophase
The Cell 61Chapter 6Microtubular arrays:Cilia and Flagella
Microtubules can form into specialized structures called:- Cilia- Flagella- Both have a unique 9 + 2 pattern.
The Cell 62Chapter 6
Structure of a Flagellum9 & 2
The Cell 63Chapter 6
Review
Cell TheoryCell Size What restricts cell size?
Prokaryotic CellsEukaryotic Cells
Organelles Know the structure and functions of the following:
Nucleus Endomembrane System Cytoskeleton Centrioles, Cilia, and Flagella
How are these cells different?
A Tour of the Cell
Chapter 6
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