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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Review of normal cellular
structure and function
2
Introduction• The basic organizational structure of the human body is the cell.
• There are 50-100 trillion cells in the human body.
• Differentiation is when cells specialize.
• As a result of differentiation, cells vary in size and shape due to their unique function.
3
A Composite Cell
• Also called a ‘typical’ cell• Major parts include:
• Nucleus• contains DNA
• Cytoplasm• cellular contents
between plasma membrane &nucleus
• Cell membrane• selective barrier
Microtubules
Flagellum
Nuclear envelope
Basal body
Chromatin
Ribosomes
Cell membrane
Mitochondrion
Cilia
Microtubules
Microtubule
Centrioles
Microvilli
Lysosomes
Nucleolus
Nucleus
Phospholipid bilayer
SmoothEndoplasmicreticulum
RoughEndoplasmicreticulum
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Golgiapparatus
Secretoryvesicles
4
Cell Membrane(aka Plasma Membrane)
• Outer limit of the cell• Controls what moves in and out of the cell• Selectively permeable• Phospholipid bilayer
• Water-soluble “heads” form surfaces (hydrophilic)• Water-insoluble “tails” form interior (hydrophobic)• Permeable to lipid-soluble substances
• Cholesterol stabilizes the membrane• Proteins:
• Receptors• Pores, channels and carriers• Enzymes• Self-markers
5
Cell Membrane
Cell membraneCell membrane
(b)(a)
“Heads” ofphospholipid
“Tails” ofphospholipid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Biophoto Associates/Photo Researchers, Inc.
Fibrous proteinCarbohydrateGlycolipidGlycoprotein
Extracellular sideof membrane
Cytoplasmic sideof membrane
Cholesterolmolecules
Globularprotein
Doublelayer ofPhospholipidmolecules
Hydrophobicfatty acid“tail”
HydrophilicPhosphate“head”
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cell MembraneElectrochemical Gradient
• due to selective permeability
• difference in concentration of chemicals across membrane
• difference in distribution of charges across the membrane
• difference is the membrane potential
7
Cell Adhesion Molecules (CAMs)
• Guide cells on the move
• Selectin – allows white blood cells to “anchor”
• Integrin – guides white blood cells through capillary walls
• Important for growth ofembryonic tissue
• Important for growth of nerve cells
Adhesion
White blood cell
Integrin
Selectin
Exit
Splinter
Attachment(rolling)
Blood vessellining cell
Carbohydrateson capillary wall
Adhesionreceptor proteins
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8
Cytoplasm
• Cytosol = water
• Organelles = solids
Cytoplasm is really like a Jello fruit salad where the Jello is the cytosol and the fruits (oranges, grapes, bananas,
maybe walnuts, etc.) are the organelles.
9
OrganellesEndoplasmic Reticulum (ER)
• Connected, membrane-bound sacs, canals, and vesicles• Transport system• Rough ER
• Studded with ribosomes• Smooth ER
• Lipid synthesis• Added to proteinsarriving from rough ER
• Break down of drugsRibosomes
• Free floating or connected to ER• Provide structural support and enzyme activityto amino acids to form protein (protein synthesis)
Membranes
Ribosomes
Membranes
(b) (c)
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10
OrganellesGolgi apparatus• Stack of flattened, membranous sacs• Modifies, packagesand delivers proteins
Vesicles• Membranous sacs• Store substances
Inner membrane
Outer membrane
Cristae
(a) (b)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Bill Longcore/Photo Researchers, Inc.
Mitochondria• Membranous sacs with inner partitions• Generate energy
11
Organelles
Lysosomes• Enzyme-containing sacs• Digest worn out cell parts or unwanted substances
Peroxisomes• Enzyme-containing sacs• Break down organic molecules
Centrosome• Two rod-like centrioles• Used to produce cilia and flagella• Distributes chromosomes during cell division
(a) (b)
Centriole(cross-section)
Centriole(longitudinal section)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Don W. Fawcett/Visuals Unlimited
12
Organelles
Cilia• Short hair-like projections• Propel substances on cell surface
Flagellum• Long tail-like projection• Provides motility to sperm
(a)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Oliver Meckes/Photo Researchers, Inc.
© Colin Anderson/Brand X/CORBIS
13
Microfilaments and microtubules• Thin rods and tubules• Support cytoplasm• Allows for movement of organelles
Organelles
Inclusions
• Temporary nutrients and pigments
Microtubules
Microfilaments
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© M. Schliwa/Visuals Unlimited
14
Cell Nucleus
• Is the control center of the cell
• Nuclear envelope• Porous double membrane• Separates nucleoplasm from cytoplasm
• Nucleolus• Dense collection of RNA and proteins• Site of ribosome production
• Chromatin• Fibers of DNA and proteins• Stores information for synthesis of proteins
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Nucleus
Nucleolus
Chromatin
(a)
Nuclearpores
Nuclearenvelope
15
Movements Into and Out of the Cell
Passive (Physical) Processes
• Require no cellular energy and include:
• Simple diffusion• Facilitated diffusion• Osmosis• Filtration
Active (Physiological) Processes• Require cellular energy and include:
• Active transport• Endocytosis• Exocytosis• Transcytosis
16
Simple Diffusion
• Movement of substances from regions of higher concentration to regions of lower concentration• Oxygen, carbon dioxide and lipid-soluble substances
Time
Solute molecule
Water molecule
A B A B
(2) (3)
Permeablemembrane
A B
(1)
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17
Animation:How Diffusion Works
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18
Facilitated Diffusion• Diffusion across a membrane with the help of a channel or carrier molecule• Glucose and amino acids
Region of higherconcentration
Transportedsubstance
Region of lowerconcentration
Protein carriermolecule
Cellmembrane
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19
Animation:How Facilitated Diffusion
Works
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20
Osmosis• Movement of water through a selectively permeable membrane from regions of higher concentration to regions of lower concentration• Water moves toward a higher concentration of solutes
Time
Protein molecule
Water molecule
A
B
A B
(1) (2)
Selectivelypermeablemembrane
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
21
Animation:How Osmosis Works
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22
Osmosis and Osmotic Pressure
• Osmotic Pressure – ability of osmosis to generateenough pressure to move a volume of water
• Osmotic pressure increases as the concentrationof nonpermeable solutes increases
• Isotonic – same osmotic pressure• Hypertonic – higher osmotic pressure (water loss)• Hypotonic – lower osmotic pressure (water gain)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© David M. Phillips/Visuals Unlimited
(b)
(a)
(c)
23
Filtration
• Smaller molecules are forced through porous membranes• Hydrostatic pressure important in the body• Molecules leaving blood capillaries
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Capillary wall
Larger molecules
Smaller molecules
Bloodpressure Blood
flow
Tissue fluid
24
Active Transport
• Carrier molecules transport substances across a membrane from regions of lower concentration to regions of higher concentration• Sugars, amino acids, sodium ions, potassium ions, etc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Carrier protein Binding site
(a)
(b)
Cel
l mem
bra
ne
Carrier proteinwith altered shape
Phospholipidmolecules Transported
particle
Cellularenergy
Region of higherconcentration
Region of lowerconcentration
25
Active Transport:Sodium-Potassium Pump
• Active transport mechanism• Creates balance by “pumping” three (3) sodium (Na+) OUT and two (2) potassium (K+) INTO the cell• 3:2 ratio
26
Animation:How the Sodium-Potassium
Pump Works
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Secondary Active Transport• uses the energy stored in a concentration gradient
– the gradient is established through active transport• symporters move substances in the same direction while
antiporters move substances in opposite directions
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Endocytosis• Cell engulfs a substance by forming a vesicle around the substance• Three types:
• Pinocytosis – substance is mostly water• Phagocytosis – substance is a solid• Receptor-mediated endocytosis – requires the substance to bind to a membrane-bound receptor
Nucleus Nucleolus
Particle VesiclePhagocytizedparticle
Cellmembrane
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29
Endocytosis
Cytoplasm
Vesicle
(a) (b) (c) (d)
Receptorprotein
Cellmembrane
Moleculesoutside cell
Cellmembraneindenting
Receptor-ligandcombination
Nucleus Nucleolus
Particle VesiclePhagocytizedparticle
Cellmembrane
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30
Exocytosis• Reverse of endocytosis• Substances in a vesicle fuse with cell membrane• Contents released outside the cell• Release of neurotransmitters from nerve cells
Nucleus
Endoplasmicreticulum
Golgiapparatus
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31
The Cell Cycle
• Series of changes a cell undergoes from the time it forms until the time it divide• Stages:
• Interphase• Mitosis• Cytokinesis
Apoptosis
G2 phase
Prophase
Metaphase
AnaphaseTelophase
Cytokinesis
Restrictioncheckpoint
Remainspecialized
Proceedto division
S phase:geneticmaterialreplicates
G1 phasecell growth
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32
Interphase
• Very active period• Cell grows• Cell maintains routine functions• Cell replicates genetic material to prepare for nuclear division• Cell synthesizes new organelles to prepare for cytoplasmic division• Phases:
• G phases – cell grows and synthesizes structures other than DNA• S phase – cell replicates DNA
33
Mitosis
• Produces two daughter cells from an original somatic cell• Nucleus divides – karyokinesis• Cytoplasm divides – cytokinesis • Phases of nuclear division:
• Prophase – chromosomes form; nuclear envelope disappears• Metaphase – chromosomes align midway between centrioles• Anaphase – chromosomes separate and move to centrioles• Telophase – chromatin forms; nuclear envelope forms
34
Mitosis
Telophase and CytokinesisNuclear envelopes begin toreassemble around two daughternuclei. Chromosomes decondense.Spindle disappears. Division ofthe cytoplasm into two cells.
AnaphaseSister chromatids separate toopposite poles of cell. Eventsbegin which lead to cytokinesis.
MetaphaseChromosomes align alongequator, or metaphase plateof cell.
ProphaseChromosomes condense andbecome visible. Nuclearenvelope and nucleolusdisperse. Spindle apparatusforms.
Late InterphaseCell has passed therestriction checkpointand completed DNAreplication, as well asreplication of centriolesand mitochondria, andsynthesis of extramembrane.
Early Interphaseof daughter cells—a time of normal cellgrowth and function.
Cleavagefurrow
Nuclearenvelopes
Nuclearenvelope
Chromatinfibers
Chromosomes
Spindle fiber
Centromere
Aster
Centrioles
Late prophase
Sisterchromatids
Microtubules
Mitosis
Cytokinesis
S phase
G1 phase
Interphase
Restrictioncheckpoint
(a)
(b)
(c)(d)
(e)
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© Ed Reschke
G2 phase
35
Animation:Mitosis and Cytokinesis
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36
Cytoplasmic Division
• Also known as cytokinesis • Begins during anaphase• Continues through telophase• Contractile ring pinches cytoplasm in half
37
Animation:Control of the Cell Cycle
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38
3.5: Control of Cell Division• Cell division capacities vary greatly among cell types
• Skin and blood cells divide often and continually• Neuron cells divide a specific number of times then cease
• Chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock
• Cells divide to provide a more favorable surface area to volume relationship
• Growth factors and hormones stimulate cell division• Hormones stimulate mitosis of smooth muscle cells in uterus• Epidermal growth factor stimulates growth of new skin
• Tumors are the consequence of a loss of cell cycle control
• Contact (density dependent) inhibition
39
Tumors• Two types of tumors:
• Benign – usually remains localized• Malignant – invasive and can metastasize; cancerous
• Two major types of genes cause cancer:
• Oncogenes – activate other genes that increase cell division• Tumor suppressor genes – normally regulate mitosis; if inactivated they are unable to regulate mitosis
• Cells are now known as “immortal”
Normal cells(with hairlike cilia)
Cancer cells
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© Tony Brain/Photo Researchers, Inc.;
40
Animation:How Tumor Suppressor Genes
Block Cell Division
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41
3.6: Stem and Progenitor Cells
• Stem cell:• Can divide to form two new stem cells
• Self-renewal• Can divide to form a stem cell and a progenitor cell• Totipotent – can give rise to every cell type• Pluripotent – can give rise to a restricted number of cell types
• Progenitor cell:• Committed cell• Can divide to become any of a restricted number of cells • Pluripotent
42
Stem and Progenitor Cells
one or more steps
Sperm
Egg
Fertilizedegg
Stem cell
Stem cell
Progenitor cell
Progenitorcell
Progenitorcell
Blood cells and platelets
Fibroblasts (a connective tissue cells)
Bone cells
Progenitorcell
Astrocyte
Neuron
Skin cell
Sebaceousgland cell
produces another stem cell(self-renewal)
Progenitorcell
Progenitorcell
Progenitorcell
Progenitorcell
Progenitorcell
Progenitorcell
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43
3.7: Cell Death
Apoptosis:
• Programmed cell death
• Acts as a protective mechanism
• Is a continuous process