1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Review of
normal
cellular
structure and
function

2. 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. 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
Smooth
Endoplasmic
reticulum
Rough
Endoplasmic
reticulum
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Golgi
apparatus
Secretory
vesicles

4. 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. 5
Cell Membrane
Cell membraneCell membrane
(b)(a)
“Heads” of
phospholipid
“Tails” of
phospholipid
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a: © Biophoto Associates/Photo Researchers, Inc.
Fibrous proteinCarbohydrateGlycolipid
Glycoprotein
Extracellular side
of membrane
Cytoplasmic side
of membrane
Cholesterol
molecules
Globular
protein
Double
layer of
Phospholipid
molecules
Hydrophobic
fatty acid
“tail”
Hydrophilic
Phosphate
“head”
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6. Cell Membrane
Electrochemical 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. 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 of
embryonic tissue
• Important for growth of nerve
cells
Adhesion
White blood cell
Integrin
Selectin
Exit
Splinter
Attachment
(rolling)
Blood vessel
lining cell
Carbohydrates
on capillary wall
Adhesion
receptor proteins
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8. 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. 9
Organelles
Endoplasmic Reticulum (ER)
• Connected, membrane-bound
sacs, canals, and vesicles
• Transport system
• Rough ER
• Studded with ribosomes
• Smooth ER
• Lipid synthesis
• Added to proteins
arriving from rough ER
• Break down of drugs
Ribosomes
• Free floating or connected to ER
• Provide structural support and enzyme activity
to amino acids to form protein (protein synthesis)
Membranes
Ribosomes
Membranes
(b) (c)
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10. 10
Organelles
Golgi apparatus
• Stack of flattened,
membranous sacs
• Modifies, packages
and delivers proteins
Vesicles
• Membranous sacs
• Store substances
Inner membrane
Outer membrane
Cristae
(a) (b)
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a: © Bill Longcore/Photo Researchers, Inc.
Mitochondria
• Membranous sacs with
inner partitions
• Generate energy

11. 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)
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a: © Don W. Fawcett/Visuals Unlimited

12. 12
Organelles
Cilia
• Short hair-like projections
• Propel substances on cell
surface
Flagellum
• Long tail-like projection
• Provides motility to sperm
(a)
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© Colin Anderson/Brand X/CORBIS

13. 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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14. 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
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Nucleus
Nucleolus
Chromatin
(a)
Nuclear
pores
Nuclear
envelope

15. 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. 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)
Permeable
membrane
A B
(1)
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17. 17
Animation:
How Diffusion Works
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18. 18
Facilitated Diffusion
• Diffusion across a membrane with the help of a channel or
carrier molecule
• Glucose and amino acids
Region of higher
concentration
Transported
substance
Region of lower
concentration
Protein carrier
molecule
Cell
membrane
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19. 19
Animation:
How Facilitated Diffusion
Works
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20. 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)
Selectively
permeable
membrane
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21. 21
Animation:
How Osmosis Works
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22. 22
Osmosis and Osmotic
Pressure
• Osmotic Pressure – ability of osmosis to generate
enough pressure to move a volume of water
• Osmotic pressure increases as the concentration
of nonpermeable solutes increases
• Isotonic – same osmotic
pressure
• Hypertonic – higher osmotic
pressure (water loss)
• Hypotonic – lower osmotic
pressure (water gain)
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© David M. Phillips/Visuals Unlimited
(b)
(a)
(c)

23. 23
Filtration
• Smaller molecules are forced through porous membranes
• Hydrostatic pressure important in the body
• Molecules leaving blood capillaries
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Capillary wall
Larger molecules
Smaller molecules
Blood
pressure Blood
flow
Tissue fluid

24. 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.
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Carrier protein Binding site
(a)
(b)
Cellmembrane
Carrier protein
with altered shape
Phospholipid
molecules Transported
particle
Cellular
energy
Region of higher
concentration
Region of lower
concentration

25. 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. 26
Animation:
How the Sodium-Potassium
Pump Works
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27. 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

28. 28
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 VesiclePhagocytized
particle
Cell
membrane
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29. 29
Endocytosis
Cytoplasm
Vesicle
(a) (b) (c) (d)
Receptor
protein
Cell
membrane
Molecules
outside cell
Cell
membrane
indenting
Receptor-ligand
combination
Nucleus Nucleolus
Particle VesiclePhagocytized
particle
Cell
membrane
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30. 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
Endoplasmic
reticulum
Golgi
apparatus
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31. 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
Cytokinesis
Restriction
checkpoint
Remain
specialized
Proceed
to division
S phase:
genetic
material
replicates
G1 phase
cell growth
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32. 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. 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. 34
Mitosis
Telophase and Cytokinesis
Nuclear envelopes begin to
reassemble around two daughter
nuclei. Chromosomes decondense.
Spindle disappears. Division of
the cytoplasm into two cells.
Anaphase
Sister chromatids separate to
opposite poles of cell. Events
begin which lead to cytokinesis.
Metaphase
Chromosomes align along
equator, or metaphase plate
of cell.
Prophase
Chromosomes condense and
become visible. Nuclear
envelope and nucleolus
disperse. Spindle apparatus
forms.
Late Interphase
Cell has passed the
restriction checkpoint
and completed DNA
replication, as well as
replication of centrioles
and mitochondria, and
synthesis of extra
membrane.
Early Interphase
of daughter cells—
a time of normal cell
growth and function.
Cleavage
furrow
Nuclear
envelopes
Nuclear
envelope
Chromatin
fibers
Chromosomes
Spindle fiber
Centromere
Aster
Centrioles
Late prophase
Sister
chromatids
Microtubules
Mitosis
Cytokinesis
S phase
G1 phase
Interphase
Restriction
checkpoint
(a)
(b)
(c)(d)
(e)
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© Ed Reschke
G2 phase

35. 35
Animation:
Mitosis and Cytokinesis
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36. 36
Cytoplasmic Division
• Also known as cytokinesis
• Begins during anaphase
• Continues through telophase
• Contractile ring pinches cytoplasm in half

37. 37
Animation:
Control of the Cell Cycle
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38. 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. 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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40. 40
Animation:
How Tumor Suppressor Genes
Block Cell Division
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41. 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. 42
Stem and Progenitor Cells
one or more steps
Sperm
Egg
Fertilized
egg
Stem cell
Stem cell
Progenitor cell
Progenitor
cell
Progenitor
cell
Blood cells and platelets
Fibroblasts (a connective tissue cells)
Bone cells
Progenitor
cell
Astrocyte
Neuron
Skin cell
Sebaceous
gland cell
produces another stem cell
(self-renewal)
Progenitor
cell
Progenitor
cell
Progenitor
cell
Progenitor
cell
Progenitor
cell
Progenitor
cell
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43. 43
3.7: Cell Death
Apoptosis:
• Programmed cell death
• Acts as a protective mechanism
• Is a continuous process