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The microscope was invented in the 17thcentury
Using a microscope, Robert Hooke discoveredcells in 1665: cellulae
INTRODUCTION TO THE WORLDOF THE CELL
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The light microscope enables us to see the overallshape and structure of a cell
Microscopes: windows to the world of thecell
Image seen by viewer
Eyepiece
Ocular
lens
Objective lensSpecimen
Condenser lens
Light source
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Electron microscopes were 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
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Scanningelectron
microscope(SEM)
Scanning
electronmicrograph ofcilia
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Transmissionelectron
microscope(TEM)
Transmission
electronmicrograph ofcilia
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The cell theorystates:
All organisms are composed of one or more cells.
Cells are the basic unit of structure and function inorganisms.
All cells come only from other cells.
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Cells are smallso they can exchange materials
with their surroundings.
Surface area relative to the volume decreases assize of cell increases.
- limits the size of cells
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Sizes of living things
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All cells have:
Plasma membrane
Region where DNA is stored Cytoplasm
2 Types:
- Prokaryotic
- Eukaryotic
Cells
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Domains: Archaebacteria and Eubacteria
Kingdom Monera
DNA is NOT enclosed in nucleus
Generally the smallest, simplest cells
No membrane bound organelles
Prokaryotic cells
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A prokaryotic cell is enclosed by a plasmamembrane and is usually encased in a rigid cell
wall
The cell wallmay be
covered by asticky capsule RibosomesCapsule
Cell wall
Plasma
membrane
Prokaryotic
flagella
Nucleoid region
(DNA)Pili
Inside the cell
are its DNAand otherparts
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Domain Eukarya
Plantae
Animalia
Protista
Fungi
Larger and more complex than prokaryotic cells Have a nucleus and other organelles
Eukaryotic cells
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An animal cell
Plasma membrane
Golgiapparatus
Ribosomes
NucleusSmooth
endoplasmic
reticulumRoughendoplasmic
reticulum
Mitochondrion
Not in
most
plant
cells
Cytoskeleton
Flagellum
Lysosome
Centriole
Peroxisome
Microtubule
Intermediate
filament
Microfilament
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Plant cells have structures that animal cells
lacks:
Chloroplasts
A rigid cell wall composed of cellulose
vacuole
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Nucleus
Golgi
apparatus
Not in
animal
cells
Centralvacuole
Chloroplast
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Rough
endoplasmic
reticulum
Ribosomes
Smooth
endoplasmic
reticulum
Cytoskeleton
Microtubule
Intermediate
filament
Microfilament
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Eukaryotic cells living factories
A Tour of the Cell
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Cell Function
Cells are the building blocks of all plants and animals
Cells are produced by the division of preexistingcells
Cells are the smallest units that perform all vitalphysiological functions
Each cell maintains homeostasis at the cellular
level
Homeostasis at higher levels reflects combined,coordinated action of many cells
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Cytology-the study of the structure and
function of cells
Cell biology
The human body contains both somatic and sex cells
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The Anatomy of a Representative Cell
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Is surrounded by extracellular fluid, which is the
interstitial fluid of the tissue
A typical cell
Has an outer boundary called the cell membrane
or plasma membrane
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A Typical Cell
1. Has structural components - cytoskeleton(made up of protein filaments)
2. Has organelles that perform specificfunctions in the cell (Mitochondria
-produces energy)
3. Has certain active genes to give the cell aspecific function (heart cells, liver cells,brain cells, etc)
4. Has the information to perpetuate thewhole organism as well as its specificfunction (Nucleus - DNA)
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Nonmembranous organelles are not enclosed by
a membrane and always in touch with the cytosol
Organelles
Cytoskeleton, microvilli, centrioles, cilia,ribosomes, proteasomes
Membranous organelles are surrounded by lipidmembranes
Endoplasmic reticulum, Golgi apparatus,
lysosomes, peroxisomes, mitochondria
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Different Types of Cell Movement (related tostructural components)
Internal - movement of proteins, molecules,organelles
External - movement of molecules into or out of the cellDetermined by cell membrane function and dynamics
Determined by cytoskeleton dynamics
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Physical isolation
Cell membrane functions include:
Regulation of exchange with the environment
Changes in ECF, pH, receptorrecognition
Structural support
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The cell membrane is a phospholipid bilayer with
proteins, lipids and carbohydrates.
The Cell Membrane
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Membrane StructureMembrane Structure
Primarily made up of lipids
With lipids
With carbohydrates
1. Lipids are the most abundant
Membrane called phospholipid bilayer
Outermost portions - hydrophilic
Innermost layers - hydrophobic
P bilit
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The ease with which substances can cross the cell membrane
Permeability
Nothing passes through an impermeable barrier
Anything can pass through a freely permeable
barrier
Cell membranes are selectively permeable
Selective permeability is based on size, electrical charges, molecular
shape, and lipid solubility.
Transport of substances across the membrane can be Passive or ActiveActive transport requires energy to occur
Passive transport does not require energy
Diffusion, Osmosis and Active Transport are different types of movement
Diff i h C ll M b
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Diffusion across the Cell Membrane
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Cell Motility
The movement of whole cells is made possible throughthe membrane pliability and the rearrangement of thecytoskeleton and internal components
C t k l t id t th fl ibilit d
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Microfilaments(6nm) -
1. anchor cytockeleton to integral proteins,2. determine the consistency of the cytoplasm,
3. interacts with myosin to produce movement
Cytoskeleton provides strength, flexibility andmotility
Intermediate filaments (7-11 nm)- Protein compositionvaries between cell types.
1. Strengthen cell and help maintain shape;
2. Stabilize the position of organelles
3. Stabilize the position of the cell with respect to surrounding cells thru
specialized membrane attachments
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Microtubules (up to 25nm)all cells contain microtubules, made up ofprotein tubulin. Largest cytoskeletal component
Functions:
1. Primary cytoskeletal component
2. Disassembly of microtubules provides a mechanism forchanging the shape of the cell and assisting in movement
3. Used to transport other proteins around the cell in association
with motor proteins kinesin and dynein
4. Forms spindle apparatus during cell division
5. Form structural cell components such as cilia and centrioles
Th C t k l t
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The Cytoskeleton
Th E d l i R ti l
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The Endoplasmic Reticulum
Site of protein and lipid synthesis
Th G l i A t
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The Golgi Apparatus
Forms secretory vesicles
Forms new membrane components
F ti f th G l i A t
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Functions of the Golgi Apparatus
L a d P i
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Lysosomes are
Lysosomes and Peroxisomes
Filled with digestive enzymes
Responsible for autolysis of injured cells
Peroxisomes
Carry enzymes that neutralize toxins
Lysosome Functions
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Lysosome Functions
Mitochondria
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Responsible for ATP production through aerobicrespiration
Mitochondria
Matrix = fluid contents of mitochondria
Cristae = folds in inner membrane
The nucleus is the center of cellular operations
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Surrounded by a nuclear envelope
The nucleus is the center of cellular operations
Perinuclear space
Communicates with cytoplasm through
nuclear pores
The Nucleus
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The Nucleus
Contents of the nucleus
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A supportive nuclear matrix
Contents of the nucleus
One or more nucleoli
Chromosomes
DNA bound to histones
Chromatin
Chromosome Structure
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Chromosome Structure
The genetic code
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The cells information storage system
The genetic code
Triplet code
A gene contains all the triplets needed to codefor a specific polypeptide
Gene activation and protein synthesis
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Gene activation initiates with RNA polymerasebinding to the gene
Gene activation and protein synthesis
Transcription is the formation of mRNA fromDNA
mRNA carries instructions from the nucleusto the cytoplasm
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The Cell Life Cycle
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DNA Replication
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DNA Replication
Early Prophase -
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Early Prophase Mitosis Begins
Duplicated chromosomes begin to condense
Nucleoli dissappear
centrosome(with centriole pairs)
Late Prophase
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Late Prophase
One centriole pair of thecentrosome is moved toward
opposite pole of spindle
Mitotic spindle forms Spindle fibers attach to
sister chromatids
Nuclear envelope starts to
break up
centriole
Mitotic
spindle
kinetochore
Metaphase
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Metaphase
All chromosomes arelined up at the
metaphase plate(equator)
Chromosomes aremaximally condensed
Anaphase
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Anaphase
Sister chromatids arepulled apart at thecentromere
Once separated, eachchromatid is achromosome
Each identical
chromosome movestoward opposite poles
Telophase
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Telophase
Chromosomes uncoil,
return to chromatin
Two nuclear membranesform, one around each set of
new chromosomes
Nucleoli reappear
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INTERPHASE PROPHASE
Centrosomes(with centriole pairs)
Chromatin
Nucleolus Nuclearenvelope
Plasmamembrane
Early mitoticspindle
Centrosome
CentromereChromosome,consisting of twosister chromatids
Fragmentsof nuclearenvelope
Kinetochore
Spindlemicrotubules
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METAPHASE TELOPHASE AND CYTOKINESIS
Metaphaseplate
Spindle Daughter chromosomes
Cleavagefurrow
Nucleolusforming
Nuclearenvelopeforming
ANAPHASE
Two Mechanisms of Cytokinesis
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Cytokinesis is thedivision of the cytoplasm
In animals, cytokinesisoccurs by cleavage
This process pinches thecell apart
Two Mechanisms of Cytokinesis
Cleavagefurrow
Cleavagefurrow
Contracting ring ofmicrofilaments
Daughter cells
Cell plate Wall of Daughter
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In plants, amembranous cellplate splits the cell intwo
pforming parent cell
gnucleus
Results of Mitosis
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Results of Mitosis
Two daughter nuclei
Each with same
chromosome number asparent cell
Each cell is geneticallyidentical
Review of the functions of mitosis:
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Multicellular organisms
Growth
Cell replacement
Some protistans, fungi, plants, animals
Asexual reproduction
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When the cell cycle operates normally, mitoticcell division functions in:
Growth (seen here in an onion root)
Cell eplacement (seen he e in skin)
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Cell replacement (seen here in skin)
Deadcells
Dividingcells
Epidermis,the outerlayer of theskin
Dermis
Asexual reproduction (seen here in a hydra)
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Asexual reproduction (seen here in a hydra)
Budding of a
new hydra
Growth factors signal the cell cycle control system
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Proteins within the cell control the cell cycle
growth factors deliver signals that determinewhether the cell will go through a complete
cycle and divide
Growth factors signal the cell cycle control system
G1 checkpoint
M checkpoint G2 checkpoint
Controlsystem
Th bi di f th f t t ifi
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The binding of growth factors to specificreceptors on the plasma membrane is usuallynecessary for cell division
Growth factor
Cell cyclecontrolsystem
Plasma membrane
Receptorprotein
Signaltransduction
pathway
G1 checkpointRelayproteins
Cancer:
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Cancer cells have abnormal cell cycles
They divide excessively and can form abnormal
masses called tumors
Cancer cells ignore the control signals of normalcells - ignore STOP signals
Radiation and chemotherapy are effective ascancer treatments because they interfere with celldivision
cells growing out of control
Malignant tumors can invade other tissues and
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Malignant tumors can invade other tissues andmay lead to death
Tumor
Glandulartissue
1 2 3A tumor growsfrom a singlecancer cell.
Cancer cells invadeneighboring tissue.
Lymphvessels
Cancer cells spreadthrough lymph andblood vessels to otherparts of the body.
Metastasis
cell division
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Cell division is the reproduction of cells
cell division
Apoptosis is the genetically controlled death ofcellsMitosis is the nuclear division of somatic cells
Meiosis produces sex cells
Differentiation
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Process of specialization
Differentiation
Results from inactivation of particular genes
Produces populations of cells with limitedcapabilities
Differentiated cells form tissues
Quiz
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1. Name the stages of the cell cycle in order of
occurrence.2. What happens in the S stage of interphase?
3. What are the two main stages of cell division inthe cell cycle?
4. What are the main stages of mitosis (M phase)of the cell cycle?
5. What mechanism do animal cells use incytokinesis?
6. Why is cancer considered a disease of the cellcycle?
QUIZ:
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I. FILL IN THE BLANK
1. The first person to describe microscopic organisms and livingcells was
__________________________. 2. Short, hair-likeorganelles that can move and may cover a unicellular organism orline the respiratory tract are called
__________________________. 3. Some ribosomes arefree in the cytoplasm, while others line the membrane of the
_________________________. 4. Everything between the
cell membrane and the nucleus is the cell's____________________. 5. All cells, from all organisms, aresurrounded by a _________________________. 6. Theorganelle that stores DNA and synthesizes RNA
______________________. 7. The organelle that processesand packages substances produced by the cell
___________________________. 8. The_______________________is the control center of the cell.9. The DNA in the form of a long strand is called
_____________________. 10. Scientist call the modern viewof the cell membrane structure the
_________________________________.
QUIZ CONT
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11. During cell division, _________________________strands coil and condense into thick structures called12._______________________. 13. Organisms whose cellsnever contain a membrane bound nucleus are called_______________________. 14. Suspended in the cell'scytosol are tiny _______________________. 15. When a
cell prepares to reproduce the _______________________disappears. 16. In eukaryotic cells, most organelles aresurrounded by a _____________________. 17. Organismswhose cells always or usually contain a nucleus or nuclei arecalled __________________18. Unicellular organisms suchas bacteria and their relatives are___________________________. 19. Where are poisonsand waste detoxified in a cell?______________________20. A cell synthesizes protein byusing organelles called _____________________.