Transcript 1.2b Cells

CELL STRUCTURE AND
FUNCTION
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Body Organization
• The fundamental units that make up all
living things are called cells.
• When cells cluster together and perform
the same function, they are called tissues.
• When tissues cluster together and perform
the same function, they are called organs.
• Organs cluster together to form organ
systems, which result in the total
organism.
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Organization
Cells Tissues  Organs
 Organ systems  Organism
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All Cells On Earth
• Are enclosed in a membrane that
maintains internal conditions different
from the surroundings.
• Have DNA as the genetic material.
• Can interconvert forms of energy.
• Can interconvert chemical materials.
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Every cell has three things in common:
• Metabolism (using up oxygen and sugars).
• Responds to its environment
• Capable of maintaining homeostasis within
itself and within the body.
– HOMEOSTASIS is maintaining a balanced
internal environment, such as temperature,
pH, glucose levels, etc.
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CELL ORGANIZATION
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CYTOPLASM
• Jelly-like substance in the cell around the organelles.
• This is where many of the chemical activities (cellular
metabolism) of the cell occur.
• Cytoplasm contains mostly water and things dissolved in
water (sugars like glucose, and energy molecules =ATP)
Cytoskeleton: made up of long protein fibers that extend
throughout cytoplasm.
1) Maintains cell shape
2) Movement
a) muscle cell contraction
b) moving organelles within the cell
c) moving the cell itself
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ORGANELLES
• Small structures (miniature organs) that occur
within the cell and have various functions.
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PLASMA MEMBRANE
NUCLEUS
MITOCHONDRIA
ENDOPLASMIC RETICULUM
GOLGI COMPLEX
VESICLES
CILIA AND FLAGELLA
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PLASMA MEMBRANE
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Surrounds the entire cell.
Functions of the Plasma Membrane:
– Plasma membranes are selectively
permeable. This means that the plasma
membrane allows some substances to
enter or leave a cell more easily than
others.
– Communication with other cells and the
environment
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PLASMA MEMBRANE
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NUCLEUS
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Usually the largest structure in a cell.
Functions of the nucleus: Stores DNA
(genetic material that makes up
chromosomes). Our genes are on the
chromosomes) The majority of genetic
material within the cell is contained in
the nucleus
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MITOCHONDRIA
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Cells have hundreds of mitochondria.
Function of mitochondria is to make ATP
(energy molecules).
NOTE: Mitochondria must have OXYGEN to
convert nutrients to ATP for energy.
Therefore, the mitochondria are the organelles
that carry out cellular respiration, converting
the chemical energy of foods such as sugar
into the chemical energy of a molecule called
ATP.
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CELL ORGANIZATION
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RER
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ROUGH ENDOPLASMIC RETICULUM
(endoplasmic = within cytoplasm;
reticulum = network; rough = surface of
membrane covered with RIBOSOMES.
The function of ribosomes (and
therefore, function of RER) is to make
proteins.
Ribosomes make proteins out of
amino acids.
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• The messenger RNA carries the blueprint of the DNA’s
amino acid sequence into the cytoplasm; it then carries it
into the ribosomes within the RER.
• The ribosome has the RNA that translates the blueprint
into an exact copy of the original DNA strand, and the
protein is formed within the ribosome (like a protein
factory).
• The protein is then taken out and carried through the
canals of the reticulum like a boat going down a canal in
Venice. The protein then floats into the Golgi complex,
where it will be packaged for shipment like a Fed-Ex
center.
• Some of these proteins will be used to make enzymes.
Enzymes are required for the cell to undergo various
reactions. Elevated body temperatures may denature
enzymes.
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Golgi
Complex
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GOLGI COMPLEX
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The Golgi apparatus is a complex
system of membranous channels and
saccules continuous with the plasma
membrane.
Function of Golgi complex:
– Packages the proteins made by the RER
and sends them where they need to go (like
a UPS center!)
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RER to Golgi Complex
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SMOOTH ENDOPLASMIC
RETICULUM
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No ribosomes
Function of SER
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Involved in metabolism (making use of
carbohydrates (sugars) and lipids (fats).
Stores calcium (necessary for every cell)
Detoxifies harmful substances (alcohol,
drugs, etc)
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NOTE: in CSI, when they suspect poisoning,
they first look at the SER in the liver.
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VESICLES
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Spheres of membranes with something inside.
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LYSOSOMES: contains digestive enzymes to
dissolve bacteria. When a bacterium is discovered
within a cell, a lysosome bubble will fuse onto it and
release its contents in an effort to dissolve the
invader. If there was a defect in the lysosome of
a white blood cell, the bacteria could
accumulate within the cell and kill a person by
infection.
TRANSPORT VESICLES: moves material from
RER to Golgi complex, or from Golgi complex to
cell membrane, etc.
STORAGE VESICLES
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Vesicles
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CILIA AND FLAGELLA
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Some cells have hair-like structures that move
the cell.
The longer structures are called flagella and
shorter ones are cilia.
Sperm cells, for instance, have flagella, which
they use to move from one place to another.
Cells in our trachea have cilia which can move
mucous along the top of the cell (when you
cough up mucous).
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Cilia
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Flagella
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Flagella Movement
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SUMMARY OF CELL FUNCTION
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SUMMARY
OF CELL
FUNCTION
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SUMMARY OF CELL
FUNCTION
• Each cell is near a blood vessel, which gives the
cell nutrients it needs and takes products out of
the cell to distribute to the rest of the body.
• The nucleus has DNA which tells the ribosomes
what kind of proteins to make at the moment.
• The ribosomes get the amino acids from the
bloodstream to build the protein molecule.
• The protein is taken to the Golgi complex, where
it is packaged and sent to a storage vesicle.
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SUMMARY OF CELL
FUNCTION
• The cytoskeleton fibers move the vesicle to the
plasma membrane where it is released from the
cell and picked up by the bloodstream and taken
to where it is needed in the body.
• The bloodstream drops off sugars to the cell,
which are taken to the mitochondria to be
broken down into ATP, which is the energy
molecule used to fuel all the functions of the cell.
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Cellular (aerobic) Respiration
• A process whereby cells use oxygen, produce
carbon dioxide, produce energy, and form ATP.
• Breathing involves the lungs supplying oxygen to
our cells and removing carbon dioxide. We often use
the word “respiration” instead of breathing. Respiration
refers to an exchange of gases: an organism obtains
oxygen and from its environment and releases carbon
dioxide as a waste product.
• Respiration can also apply to an individual cell when it
harvests energy from food molecules; this is called
cellular respiration.
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Breathing and Cellular Respiration
• Breathing and cellular
respiration are closely
related.
• As a gymnast goes
through her routine,
her lungs take up
oxygen from the air
and pass it to her
bloodstream.
• The bloodstream
carries the oxygen to
her muscle cells.
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Breathing and Cellular Respiration
• Mitochondria in the muscle cells
use the oxygen in cellular
respiration, converting energy
from glucose to generate ATP,
which the cells then use to
contract.
• Simultaneous contraction of
thousands of cells, precisely
controlled by the nervous system,
makes the gymnast’s body move.
• The gymnast’s bloodstream and
lungs also perform the vital
function of disposing of the
carbon dioxide waste produced
by cellular respiration.
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Energy
• Our body cells require a continuous supply of
energy just to stay alive-- to keep the heart
pumping blood, to breathe, maintain body
temperature, and digest food.
• These and other life-sustaining activities use as
much as 75% of the energy a person takes in as
food during a typical day.
• Whether you are sleeping or active, your cells
are busy with cellular respiration, producing ATP
just to maintain your body.
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Riding a Bicycle
• 514 calories an hour
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Running
• 865 calories an hour
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Walking
• 200 calories an hour
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Cell Surfaces
• Protect, support, and join cells
together
• To function in a coordinated way
as part of a tissue, the cells must
have junctions, structures that
connect them to one another.
• Animal cells are embedded in a
sticky layer that helps hold the
cells together in tissues and
provide protection and support as
well. This allows contact from
one cell to another.
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Cell Walls
• Plant cell walls consist of cellulose fibers
embedded in a matrix of polysaccharides
and proteins.
• Plant cell walls are multilayered structures.
• Wood is primarily composed of plant cell
walls.
• Plant cell walls protect plant cells but they
are still a layer that is permeable to selected
substances.
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Rate of Cell Division
• The rate of cell division is close to the rate of cell
death.
• 200 billion red blood cells die every day, so 200
billion red blood cells have to be made every
day.
• Too few = anemia; too many is also a problem.
• So, the body needs to do two things:
– Control the rate of cell division
– Control the rate of cell death
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Inner Life of a Cell
• Inner Life of a Cell
• http://www.youtube.com/watch?v=yKW4F0Nu-UY
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