Transcript PowerPoint to accompany Hole’s Human Anatomy and

Chapter 3: Cells
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3.1: Introduction
Cell:
basic organizational structure of the human body
•50-100 trillion cells in the human body.
Differentiation: cell specialization
Result: cells vary in size and shape and function.
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3.2: A Composite or Typical Cell
Major parts include:
Nucleus
Cell membrane
Phospholipid bilayer
Nucleus
Chromatin
Nuclear envelope Nucleolus
Cell membrane
Cytoplasm: everything
inside cell
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Cell or Plasma Membrane
• Outer limit of the cell: inside living, outside not
• 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
“Heads” of
phospholipid
“Tails” of
phospholipid
Cell membrane Cell membrane
• Cholesterol stabilizes the membrane
Cell Membrane Proteins
Receptors
Pores, channels and carriers
Enzymes
Self-markers
CAMS
Extracellular side
of membrane
Glycolipid Carbohydrate
Fibrous protein
Glycoprotein
Double
layer of
Phospholipid
molecules
Cholesterol Globular
molecules protein
Cytoplasmic side
of membrane
Hydrophobic
fatty acid
“tail”
Hydrophilic
Phosphate
“head”
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Cell Adhesion Molecules (CAMs)
• Guide cell movement
White blood cell
• Selectin – allows white blood
cells to “anchor”
• Integrin – guides white blood
cells through capillary walls
Attachment
(rolling)
Selectin
Carbohydrates
on capillary wall
Adhesion
receptor proteins
Adhesion
Integrin
Blood vessel
lining cell
Exit
Splinter
• Important for growth of
embryonic tissue, nerve cells
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Cytoplasm
Two major components
Cytosol =
watery substance, gel-like in aperence,
matrix that makes up body of cell
Organelles =
solid structures that carry out main
functions of cell
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Organelles
Endoplasmic Reticulum (ER)
Transport system
• Rough ER
Membranes
Membranes
• Studded with ribosomes
Ribosomes
Free floating or connected to ER
Provide structural support, help
form protein
• Smooth ER
Ribosomes
(b)
(c)
Lipid synthesis: lipids added to proteins
arriving from rough ER
Break down of drugs
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Golgi apparatus
• Stack of flattened, membranous sacs
• Modifies, packages and delivers proteins
Vesicles
• Membranous sacs
• Store substances
Inner membrane
Cristae
Outer membrane
Mitochondria
(a)
(b)
• Membranous sacs with inner partitions
• Generate energy
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Lysosomes
• Enzyme-containing sacs
• Digest worn out cell parts or unwanted substances
Peroxisomes
• Enzyme-containing sacs
• Break down organic molecules
Centriole
(cross-section
)
Centrosome
•Two rod-like centrioles
•Produce cilia and flagella
•Distributes chromosomes
during cell division
Centriole
(longitudinal section)
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Cilia
• Short hair-like projections
• Propel substances on cell surface
Flagellum
• Long tail-like projection
• Provides motility to sperm
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Microfilaments and microtubules
• Thin rods and tubules
• Support cytoplasm
• Allow for movement of organelles
Microtubules
Inclusions
Temporary nutrients
and pigments
Microfilaments
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Cell Nucleus: control center of the cell
Nuclear envelope
•Porous double membrane
•Separates nucleoplasm from cytoplasm
Nucleus
Nuclear
envelope
Nucleolus
Chromatin
•Fibers of DNA and proteins
•Stores information for synthesis of proteins
Chromatin
Nuclear
pores
Nucleolus
•Dense collection of RNA and proteins
•Site of ribosome production
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3.3: Movements Into & Out of the Cell
Passive Processes: (Physical)
Require no cellular energy
Active Processes: (Physiological/biochemical)
Require cellular energy
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Simple Diffusion
Movement of substances from regions of higher concentration to
regions of lower concentration
Main action of oxygen, carbon dioxide and lipid-soluble substances
Solute molecule
Permeable
membrane
A
B
(1)
Water molecule
A
B
(2)
A
B
(3)
Time
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Facilitated Diffusion
Region of higher
concentration
Diffusion across a membrane
with the help of a channel or
carrier molecule
Transported
substance
Typical of:
Glucose and amino acids
Region of lower
concentration
Protein carrier molecule
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Cell
membrane
Osmosis
Movement of water through a
selectively permeable
Selectively permeable
membrane
membrane from regions of
higher concentration to regions
of lower concentration
A
Protein molecule
Water molecule
A
B
B
Water moves toward a
higher concentration
of solutes
(1)
(2)
Time
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Osmotic Pressure
Osmotic Pressure – ability of osmosis to generate
pressure to move a volume of water
increases as the concentration of solutes increases
Relative terms: comparing 2 solutions
(inside of cell to outside environment)
Isotonic – both have same osmotic pressure
Hypertonic – higher osmotic pressure
outside (result: cell water loss)
Hypotonic – lower osmotic pressure
outside (result: cell water gain)
(a)
(b)
(c)
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Filtration
Smaller molecules are forced through porous membranes
• Cause: Hydrostatic pressure
• Common in blood capillaries
Capillary wall
Tissue fluid
Blood
pressure
Blood
flow
Larger molecules
Smaller molecules
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Active Transport
Carrier molecules transport substances across a membrane from
regions of lower concentration to regions of higher concentration
Exs: Sugars, amino acids, sodium ions, potassium ions
Carrier protein
Binding site
Cell membrane
Region of higher
concentration
Phospholipid
molecules
Carrier protein
with altered shape
Region of lower
concentration
Transported
particle
Cellular
energy
Na-K Pump: Creates balance by “pumping” three (3) sodium
(Na+) OUT and two (2) potassium (K+) INTO the cell
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Endocytosis
Cell engulfs a substance by forming a vesicle around the substance
Three types:
• Pinocytosis – substance mostly water
• Phagocytosis – substance a solid
• Receptor-mediated endocytosis – requires substance to bind to
a membrane-bound receptor
Cell
membrane
Nucleus
Particle
Phagocytized
particle
Vesicle
Nucleolus
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Receptor-mediated endocytosis
requires substance to bind to a membrane-bound receptor
Molecules
outside cell
Receptor-ligand
combination
Vesicle
Receptor
protein
Cell
membrane
Cell
membrane
indenting
Cytoplasm
(a)
(b)
(c)
(d)
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Exocytosis
• Reverse of endocytosis
• Substances in a vesicle fuse with cell membrane
• Contents released outside the cell
Ex: Release of neurotransmitters from nerve cells
Endoplasmic
reticulum
Golgi
apparatus
Vesicle
Nucleus
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Transcytosis
Endocytosis followed by exocytosis
• Transports a substance rapidly through a cell
• EX: HIV crossing a cell layer (seen below)
Anal or
vaginal canal
HIV-infected
white blood cells
Viruses bud
HIV
Receptor-mediated endocytosis
Lining of anus
or vagina
(epithelial cells)
Exocytosis
Cell
membrane
Virus infects white blood cells
on other side of lining
Receptor-mediated
endocytosis
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3.4: The Cell Cycle
Series of changes a cell undergoes
from the time it forms until the time
it divides
Stages:
Interphase:
cell growth, structures
S phase:
genetic
Mitosis:
material
replicates
cell divison
(4 phases)
Proceed
to division
cytokinesis
cytoplasm divides
Remain
specialized
G2 phase
Cell growth
G1 phase
cell growth
Cytokinesis
Restriction
checkpoint
Apoptosis
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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
Growth factors and hormones stimulate cell division
Contact (density dependent) inhibition: presence of a certain
amount of cells stops division
Tumors: consequence of loss of cell cycle control
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Tumors
Two types:
Benign – usually remains localized
Malignant – invasive and can
metastasize; cancerous
Normal cells
(with hairlike cilia)
Genes that cause cancer:
Oncogenes – activate other
genes that increase cell division
Tumor suppressor genes –
normally regulate mitosis;
inactivated unable to regulate
mitosis
Some cancer cells (HeLa) are
now known as “immortal”
Cancer cells
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3.6: Stem and Progenitor Cells
Stem cell:
Can divide to form two new stem cells or a stem cell and a
progenitor cell
Types
Totipotent – can give rise to every cell type
Pluripotent – can give rise to a restricted number of cell types
Progenitor cell:
Committed to be a specific cell type (pluripotent)
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3.7: Cell Death
Apoptosis:
• Programmed cell death
• Acts as a protective mechanism
• Is a continuous process
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