Transcript PowerPoint to accompany Hole’s Human Anatomy and

Chapter 3
Lecture
PowerPoint
Cells
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3.1: 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.
2
3.2: A Composite Cell
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• Also called a ‘typical’
cell
• Major parts include:
• Nucleus
• contains DNA
Phospholipid bilayer
Flagellum
Nucleus
Chromatin
Nuclear envelope
Nucleolus
Rough
Endoplasmic
reticulum
Centrioles
Mitochondrion
Smooth
Endoplasmic
reticulum
• Cytoplasm
• cellular contents
between plasma
membrane &
nucleus
• Cell membrane
• selective barrier
Ribosomes
Cell membrane
Basal body
Microtubules
Microvilli
Secretory
vesicles
Cilia
Golgi
apparatus
Microtubule
Microtubules
Lysosomes
3
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
• CAMS
• Self-markers
4
Cell Membrane
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Extracellular side
of membrane
Fibrous protein
Glycolipid Carbohydrate
Glycoprotein
“Heads” of
phospholipid
Double
layer of
Phospholipid
molecules
“Tails” of
phospholipid
Cell membrane
(a)
Cell membrane
(b)
a: © Biophoto Associates/Photo Researchers, Inc.
Cholesterol Globular
molecules protein
Cytoplasmic side
of membrane
Hydrophobic
fatty acid
“tail”
Hydrophilic
Phosphate
“head”
5
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
Cell Adhesion Molecules
(CAMs)
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• 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
White blood cell
Attachment
(rolling)
Selectin
Carbohydrates
on capillary wall
Adhesion
receptor proteins
Adhesion
Integrin
Blood vessel
lining cell
Exit
Splinter
7
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.
8
Organelles
Endoplasmic Reticulum (ER)
• Connected, membrane-bound
sacs, canals, and vesicles
• Transport system
• Rough ER
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Membranes
Membranes
• Studded with ribosomes
• Smooth ER
• Lipid synthesis
• Added to proteins
arriving from rough ER
• Break down of drugs
Ribosomes
(b)
(c)
Ribosomes
• Free floating or connected to ER
• Provide structural support and enzyme activity
to amino acids to form protein (protein synthesis)
9
Organelles
Golgi apparatus
• Stack of flattened,
membranous sacs
• Modifies, packages
and delivers proteins
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Vesicles
• Membranous sacs
• Store substances
Mitochondria
• Membranous sacs with
inner partitions
• Generate energy
Inner membrane
Cristae
Outer membrane
(a)
(b)
a: © Bill Longcore/Photo Researchers, Inc.
10
Organelles
Lysosomes
• Enzyme-containing
sacs
• Digest worn out cell
parts or unwanted
substances
Centrosome
• Two rod-like centrioles
• Used to produce cilia
and flagella
• Distributes
chromosomes during cell
division
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Peroxisomes
• Enzyme-containing
sacs
• Break down organic
molecules
Centriole
(cross-section)
Centriole
(longitudinal section)
(a)
(b)
a: © Don W. Fawcett/Visuals Unlimited
11
Organelles
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Cilia
• Short hair-like projections
• Propel substances on cell
surface
Flagellum
• Long tail-like projection
• Provides motility to sperm
(a)
a: © Oliver Meckes/Photo Researchers, Inc.
12
© Colin Anderson/Brand X/CORBIS
Organelles
Microfilaments and microtubules
• Thin rods and tubules
• Support cytoplasm
• Allows for movement of
organelles
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Microtubules
Inclusions
• Temporary nutrients
and pigments
Microfilaments
© M. Schliwa/Visuals Unlimited
13
Cell Nucleus
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• 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
Nucleus
Nuclear
envelope
Nucleolus
• Chromatin
• Fibers of DNA and proteins
• Stores information for synthesis of
proteins
Chromatin
Nuclear
pores
(a)
14
3.3: 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
15
Simple Diffusion
• Movement of substances from regions of higher
concentration to regions of lower concentration
• Oxygen, carbon dioxide and lipid-soluble substances
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Permeable
membrane
A
B
(1)
Solute molecule
Water molecule
A
B
(2)
Time
A
B
(3)
16
Animation:
How Diffusion Works
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17
Facilitated Diffusion
• Diffusion across a membrane with the help of a channel or
carrier molecule
• Glucose and amino acids
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Region of higher
concentration
Transported
substance
Region of lower
concentration
Protein carrier
molecule
Cell
membrane
18
Animation:
How Facilitated Diffusion
Works
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19
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
Selectively
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Protein molecule
Water molecule
permeable
membrane
A
A
B
B
(1)
(2)
Time
20
Animation:
How Osmosis Works
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21
Osmosis and Osmotic
Pressure
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• 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)
(a)
(b)
(c)
© David M. Phillips/Visuals Unlimited
22
Filtration
• Smaller molecules are forced through porous membranes
• Hydrostatic pressure important in the body
• Molecules leaving blood capillaries
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Capillary wall
Blood
pressure
Tissue fluid
Blood
flow
Larger molecules
Smaller molecules
23
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
Cell membrane
Region of higher
concentration
Region of lower
concentration
Phospholipid
molecules
Transported
particle
(a)
Carrier protein
with altered shape
Cellular
energy
(b)
24
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
25
Animation:
How the Sodium-Potassium
Pump Works
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26
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
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
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Cell
Particle
membrane
Nucleus Nucleolus
Phagocytized
particle
Vesicle
28
Endocytosis
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Cell
Particle
membrane
Phagocytized
particle
Vesicle
Nucleus Nucleolus
Receptor-ligand
combination
Molecules
outside cell
Vesicle
Receptor
protein
Cell
membrane
Cell
membrane
indenting
Cytoplasm
(a)
(b)
(c)
29
(d)
Exocytosis
• Reverse of endocytosis
• Substances in a vesicle fuse with cell membrane
• Contents released outside the cell
• Release of neurotransmitters from nerve cells
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Endoplasmic
reticulum
Golgi
apparatus
Nucleus
30
Transcytosis
• Endocytosis followed by exocytosis
• Transports a substance rapidly through a cell
• HIV crossing a cell layer
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HIV-infected
white blood cells
Anal or
vaginal canal
Viruses bud
HIV
Receptor-mediated endocytosis
Lining of anus
or vagina
(epithelial cells)
Cell
membrane
Exocytosis
Receptor-mediated
endocytosis
Virus infects
white blood cells on
other side of lining
31
3.4: The Cell Cycle
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• Series of changes a cell
undergoes from the time it
forms until the time it divide
• Stages:
• Interphase
• Mitosis
• Cytokinesis
G2 phase
S phase:
genetic
material
replicates
G1 phase
cell growth
Proceed
to division
Remain
specialized
Apoptosis
Cytokinesis
Restriction
checkpoint
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
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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.
(a)
Early Interphase
of daughter cells—
a time of normal cell
growth and function.
Restriction
checkpoint
Nuclear
envelope
Chromatin
fibers
Centrioles
Cleavage
furrow
Prophase
Chromosomes condense and
become visible. Nuclear
envelope and nucleolus
disperse. Spindle apparatus
forms.
Aster
Microtubules
(e)
(b)
Centromere
Late prophase
Spindle fiber
Sister
chromatids
Chromosomes
Nuclear
envelopes
Telophase and Cytokinesis
Nuclear envelopes begin to
reassemble around two daughter
nuclei. Chromosomes decondense.
Spindle disappears. Division of
the cytoplasm into two cells.
(d)
(c)
Mitosis
Cytokinesis
G1 phase
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.
© Ed Reschke
S phase
G2 phase
Interphase
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
• Contact (density dependent) inhibition
• Tumors are the consequence of a loss of cell cycle control
39
Tumors
• Two types of tumors:
• Benign – usually remains
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localized
• Malignant – invasive and
Normal cells
(with hairlike cilia)
can metastasize; cancerous
• Two major types of genes
cause cancer:
• Oncogenes – activate
other genes that increase cell
division
Cancer cells
• Tumor suppressor
genes – normally regulate
mitosis; if inactivated they are
unable to regulate mitosis
• Cells are now known as
“immortal”
© 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
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Sperm
Sebaceous
gland cell
Egg
Progenitor
cell
Progenitor cell
Fertilized
egg
Skin cell
Stem cell
Progenitor
cell
Progenitor
cell
Stem cell
Neuron
Progenitor
cell
Progenitor
cell
Astrocyte
Progenitor
cell
Progenitor
cell
Progenitor
cell
Bone cells
Progenitor
cell
one or more steps
Fibroblasts (a connective tissue cells)
Blood cells and platelets
produces another stem cell
(self-renewal)
43
3.7: Cell Death
Apoptosis:
• Programmed cell death
• Acts as a protective mechanism
• Is a continuous process
44