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Cells
Cells and organelles

The building blocks
of life
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Your Body’s Cells Come in Many
Shapes and Sizes
All organisms are
composed of cells
the human body
contains trillions of
cells
There are over 200
kinds of cells in the
human body
Cells have different functions
Neurons
Red Blood Cells
Sperm
Egg
Hair Cells (Sound Receptors)
Cell Structure
Cell structure
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Three basic parts
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Cell membrane
Nucleus
Cytosol + Organelles
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Nucleus
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Cytoplasm
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Contains DNA
Directs protein synthesis →
controls cell functions
a gel that fills the interior of
the cell
Houses many organelles
Cell membrane
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forms the boundary of the cell
controls what gets into the cell
– water and food
What are the cell’s main jobs?
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Transporting materials into and out of the cell
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Synthesizing proteins
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Making ATP
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Cell movement
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Growth and repair – creating new cells
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Cell Membrane –
transport of materials into cell
Cell membrane
Ribosomes, ER-Golgi
Mitochondria
Cytoskeleton
Protects Cell
Houses Proteins Allows Transport of Materials
Connects Cells with other Cells
Cell membranes are made of
lipid
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A cell is mostly water
The rest of the cell consists of 4 types of
biological molecules:
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Lipids (fats)
Carbohydrates
Proteins
Nucleic acids
Lipids
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Fats and other molecules
that are not soluble in water
Main functions:
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dissolve in water
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Important component of cell
membranes
Store energy for the cell
All are carbon-based molecules
The cell membrane

Fat soluble
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The membrane is
composed of 2 layers
of lipids
The lipid bilayer is
made up of a special
kind of lipid called
phospholipids
Lipids are a key component
of cell membranes
The cell membrane
Water
soluble
Fat soluble
Fat soluble
Phospholipids
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Spontaneously form a lipid bilayer
When mixed with water, phospholipids
arrange themselves in two layers
Water-soluble phosphate groups attract
water; the lipid tails repel water
The cell membrane is not a static
structure
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Phospholipid bilayer
Embedded proteins
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Transport molecules
into the cell
Receive signals from
other cells
Enzymes
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Membrane function
How do molecules cross the cell
membrane?
Speed up chemical
reactions
Fluid mosaic model 1:27
http://www.youtube.com/watch?v=Qqsf_UJcfBc
Transport across membranes
Cell membranes are selective

charged molecules
and ions
−+
Some types of transport do
NOT need energy
H 2O
aquaporin
noncharged
molecules
macromolecule
−+
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Diffusion
Most require energy
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Use membrane vesicles
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phospholipid
molecule
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protein
Endocytosis
Exocytosis
Use membrane transport
proteins
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Active transport
Water cannot cross the
phospholipid bilayer
Diffusion

charged molecules
and ions
−+
H 2O
aquaporin
noncharged
molecules
−+
macromolecule
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No energy is
needed
Lipid-soluble
compounds and
gases
phospholipid
molecule
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protein
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oxygen
carbon dioxide
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charged molecules
and ions
−+
H 2O
aquaporin
noncharged
molecules
−+
macromolecule
phospholipid
molecule
protein
Water flows into and
out of the cell
through transport
proteins
Active Transport Requires Energy
Facilitated Diffusion
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Pumps from Low to High Concentration
Some molecules, like glucose, require transport proteins to
provide easier entry into the cell
Transported across the membrane from high concentration to
low concentration
No energy is required
Lower solute concentration
Solute
Higher solute concentration
Transport of really BIG
molecules
Summary
Endocytosis
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Molecules are brought
into the cell
Exocytosis
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Molecules inside the cell
exit from the cell
Both types of transport
use membrane vesicles
and require energy
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cell membrane, exo and endocytosis
 http://www.youtube.com/watch?v=K7yku3sa4Y8&NR=1
Endocytosis
Exocytosis
Cell functions
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Transporting materials into and out of the cell
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Synthesizing proteins
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Synthesizing protein
Nucleus
Organelles involved
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Nucleus
Ribosomes
ER-Golgi
Golgi
Endoplasmic
reticulum (ER)
Ribosomes 
These organelles
help assemble
proteins and move
them to various
parts of the cell
Synthesizing protein:
Ribosomes
The Nucleus
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the largest organelle in a
cell
contains a cell's genetic
library
DNA carries instructions
for making proteins
(which make up your body)
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Synthesizing protein:
ER-Golgi
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ER
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Golgi
New proteins are folded
into their proper shape in
the ER
Both ER and Golgi modify
the proteins
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Mitochondria
break down
glucose to
produce ATP
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Provide energy for the
cell
Convert the energy of
food molecules into
usable energy for the
body, or ATP
Process is called
cellular respiration
Some proteins are secreted
from the cell
Cellular respiration
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Mitochondria –
the cell’s “powerhouse”
e.g., add chains of sugars
The Golgi packages the
proteins in vesicles and
delivers them to other parts
of the cell
Ribosomes
assemble chains of
amino acids to
create a protein
Where did mitochondria come
from?
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Sugar (Glucose)
Theory of endosymbiosis
Mitochondria
• double membrane
• circular DNA
• able to replicate
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Mitochondria were once
free-living bacteria
Traded a free-living
existence for a safe and
constant environment
inside a larger cell.
Symbiotic relationship
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the sheltering cell
receives a supply of ATP
in return for protecting
the mitochondria
Maintaining Cell Shape
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Cytoskeleton – the
infrastructure of the cell
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How cells move –
Flagella and cilia
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A network of fibers that
lie underneath the cell
membrane
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Functions:
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Extensions from a cell that aid in
movement
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Helps cell maintain its
shape
Helps the cell move
Transports vesicles from
one part of the cell to
another
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Cytoskeleton microtubules are stained
with a fluorescent green dye
Contain microtubules
Flagella
propel the cell in an undulating
whiplike motion.
What human cell uses a flagellum
to move?
Cilia
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Shorter and more numerous
move in a coordinated back-andforth motion.
Fantastic vesicle traffic 2:25
http://www.youtube.com/watch?v=7sRZy9PgPvg&feature=related
What are Stem Cells?
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Embryonic stem cells
Unspecialized cells
Have the potential to form
any cell type in the body,
or pluripotent
Can keep dividing and
make unlimited copies of
themselves
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Originate as inner mass
cells in an embryo
Pluripotent - can develop
into any of the 220 cell
types of the adult
Need chemical signals to
differentiate
Ethical concerns
Stem cell research video - Ireland CD - Ch1
Adult stem cells
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Replenish cells that turnover rapidly
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iPS cells (reprogrammed cells)
Not pluripotent – they are part way
along the road to differentiation
Have the potential to develop into
most of the cells in their specific
tissue
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Found in bone marrow and skin
Stem cells in the bone marrow give
rise to the many types of blood cells:
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red blood cells, white blood cells,
platelets
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Mature body cell
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iPS cells = induced pluripotent
stem cells
Mature body cells (skin cells
or fat cells) that are
reprogrammed
Important step toward treating
diseases with a patient’s own
‘repaired’ cells