Cell Structure

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Chapter 7

• Cell Structure Function

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Section 7-1

• Life is Cellular

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• What led to the discovery of the cell?
• The Microscope
• Remember!
• Cells make up all living things.

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The Discovery of the Cell

• Early Microscopes
• Scientists didnt use microscopes until the
  1600s.
• Robert Hooke -one of the 1st to look at cells
  under a microscope.
• Gave cells their name.
• P. 169, fig. 7-1
• He was looking at dead cork cells.

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Cork Cells (Hooke)
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Robert Hooke
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• At about the same time as Hooke, Anton van
  Leeuwenhoek used a tiny microscope to look at
  pond water.
• He discovered the new world of microorganisms.

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The Cell Theory

• In 1838, Matthias Schleiden stated that all
  plants are made of cells.
• In 1839, Theodore Schwann stated that all animals
  were made of cells.
• In 1855, Rudolf Virchow stated that cells could
  only come from other cells.

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The Cell TheoryP. 170

1. All living things are made of cells.
2. Cells are the basic units of structure function
   in living things.
3. New cells are produced from existing cells.

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Exploring the Cell

• Today, modern biologists use more powerful
  microscopes techniques.
• Some of the tools they use
• Fluorescent labels light microscopy
• Able to follow molecules moving through a cell.
• Confocal light microscopy
• Scans cells w/ a laser to make 3D images of cells
  their parts.
• High-resolution video
• Enables us to make movies of cells as they grow,
  divide, develop.

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• http//www.kent.edu/projects/cell/video/fatheadmin
  now2.mpg

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Another New Method

• Electron Microscopes (EM)
• Can view things 1 million times smaller than that
  of a light microscope.
• 2 types of EMs
• Transmission Electron Microscopes (TEM)
• Scanning Electron Microscopes (SEM)

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• TEM
• Lets us see cell structures large protein
  molecules.
• Cells txs must be cut into ultra-thin slices
  before they are examined.
• 2D cross sectional image.

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• TEM

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• SEM
• 3D images of cells
• Objects dont have to be thinly sliced to view.

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• SEM

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• Remember!
• EMs can only view the nonliving.

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• In the 1990s, researches perfected a new class
  of microscope.
• The Scanning Probe Microscope
• Produces images by tracing the surfaces of
  samples w/ a fine probe.
• Can observe single atoms.
• Used to see DNA protein molecules.

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• Scanning Probe Microscope

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Prokaryotes Eukaryotes

• Cells come in all shapes sizes.
• But, all cells have 2 characteristics in common
• They have a cell membrane at some point in their
  lives.
• They contain DNA.

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• Cells fall into 2 categories based on if they
  have a nucleus.
• Nucleus large membrane bound organelle.
• Contains cells DNA.
• Controls many of the cells activities.
• Organelle specialized structure that performs
  important functions w/in the cell.
• Tiny organs

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• The 2 categories are
• Prokaryotes
• Cells dont contain a nucleus.
• Eukaryotes
• Cells do contain a nucleus.
• Pro before
• Eu true
• Karyon kernel

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Prokaryotes

• Generally smaller simpler than eukaryotic
  cells.
• Prokaryotes have DNA, but its not contained in a
  nucleus.
• All are unicellular.
• Despite their simplicity, prokaryotes
• Grow
• Reproduce
• Respond to their env.
• Some are mobile.
• Ex
• Bacteria

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Eukaryotes

• Generally larger more complex than prokaryotes.
• Eukaryotes contain membrane bound organelles a
  nucleus (DNA).
• Eukaryotes can be unicellular or multicellular.
• Ex
• Plants
• Animals
• Fungi
• Protists

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Pro-k vs. Eu-k
Prokaryotes
Eukaryotes
Nucleus Endoplasmic reticulum Golgi
apparatus Lysosomes Vacuoles Mitochondria Cytoskel
eton
Cell membrane Contain DNA
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Plant vs. Animal Cell
Animal Cells
Plant Cells
Cell membrane Ribosomes Nucleus Endoplasmic
reticulum Golgi apparatus Lysosomes Vacuoles Mitoc
hondria Cytoskeleton
Centrioles
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Section 2

• Eukaryotic Cell Structure

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Comparing the Cell to a Factory

• Organelles literally means little organs.
• Specialized structures that carry out specific
  functions in a cell.

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• Cell biologist divide cells into 2 parts
• The nucleus
• The cytoplasm
• Cytoplasm portion of the cell outside the
  nucleus.
• Cytoplasm is a gelatinous-like material.

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Cytoplasm
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Nucleus

• The nucleus is the control center of the cell.
• It contains almost all the cells DNA w/ it the
  coded instructions for making proteins other
  important molecules.
• Surrounding the nucleus is a double membrane
  called the nuclear envelope.

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• On the nuclear envelope you will find nuclear
  pores.
• Allow materials to move in out of the nucleus.
• Ex
• Proteins
• RNA
• Other molecules

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• Chromatin a granular material visible w/in the
  nucleus.
• It consists of DNA tightly coiled around
  proteins.
• Most of the time chromatin is spread throughout
  the nucleus.
• However, when a cell divides, chromatin condenses
  to form chromosomes.

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• Another structure found in most nuclei is a
  nucleolus.
• The nucleolus assembles ribosomes.
• P. 176, fig. 7-7

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Ribosomes

• Ribosomes small particles of RNA protein found
  throughout the cytoplasm.
• Ribosomes make proteins by following coded
  instructions that come from the nucleus.
• These instructions are RNA.
• Cells that are major protein producers often have
  numerous ribosomes.

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Endoplasmic Reticulum (ER)

• Endoplasmic Reticulum an internal membrane
  system in cells in which lipid components of the
  cell membrane are assembled some proteins are
  modified.

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• There are 2 portions to an ER
• The rough ER
• The smooth ER
• The rough ER
• Involved in the synthesis of proteins.
• It is said to be rough b/c it has ribosomes found
  on its surface.
• Newly made proteins enter the rough ER get
  modified.

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• The Smooth ER
• No ribosomes found on the surface.
• Contains collections of enzymes that perform
  special tasks such as
• Synthesis of membrane lipids
• Detoxification of drugs
• Liver cells tend to have a large amounts of
  smooth ER.

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• RER
• SER

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Golgi Apparatus (GA)

• Proteins made in the ER move to the Golgi
  Apparatus (GA).
• The GA looks like a stack of closely apposed
  membranes.

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• The GAs modifies, sorts, packages proteins
  other materials from the ER.
• These proteins can be stored in the cell or
  secreted out of the cell.
• Kind of like UPS.
• P. 178, fig. 7-9

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Lysosomes

• The clean up crew.
• Lysosome small organelles filled w/ digestive
  enzymes.
• Lysosomes are involved in
• Breaking down old organelles.
• Digesting foreign matter in the cell.

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• Tay-Sachs -a disease is caused by lysosomes that
  fail to properly do their job.
• Fatal by the age of 4.
• More common in eastern European Jews.

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Vacuoles

• Vacuoles an organelle that stores materials such
  as
• Water
• Salts
• Proteins
• Carbs
• Plants have large central vacuoles that can hold,
  water wastes.
• P. 179, fig. 7-10

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Mitochondria Chloroplasts

• The power plants of a cell.
• Most cells get their energy (E) in 2 ways
• Food (Heterotrophs)
• Sun (Autotrophs)

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• Mitochondria
• Can be found in almost all eukaryotic cells.
• Including plant cells.
• Converts chemical E into compounds that are easy
  for the cell to use.
• Ex ATP (Adenosine Triphosphate)

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• Mitochondria are enclosed by 2 membranes.
• An outer membrane
• An inner membrane
• Highly folded on itself.
• Creates more surface area for chemical reactions.

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• Chloroplasts
• Found in plants some other orgs.
• They capture sunlight convert it into chemical
  E by photosynthesis.
• This chemical E is then converted to ATP by
  mitochondria in the plant.
• Also surrounded by 2 membranes.
• Contains a green pigment called chlorophyll.

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• Chloroplasts

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Organelle DNA

• Chloroplasts mitochondria contain their own
  DNA.
• No other organelles do.
• It is believed that both of these organelles are
  ancient descendants of prokaryotes.
• This is called the endosymbiotic theory.

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Cytoskeleton

• Cytoskeleton a network of protein filaments that
  helps the cell maintain its shape.
• It is also involved in movement.
• The cytoskeleton is made up of
• Microfilaments
• Microtubules

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• Microfilaments
• Threadlike
• Made of actin
• Forms a tough, flexible framework that supports
  the cell.
• Also responsible for cytoplasmic movement of the
  cell.

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• Microtubules
• Hollow tube-like structures
• Made of tubulin
• Critical to maintaining cell shape.
• Also form structures called spindles during cell
  division.
• Tubulin is also used to make centrioles.
• Located near the nucleus.
• Help organize cell division.

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• Microtubules also help w/ movement.
• They make up cilia flagella.
• P. 181, fig. 7-11

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Section 7-3

• Cell Boundaries

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• All cells are surrounded by a thin barrier called
  the cell membrane.
• Many cells also have a strong supporting layer
  around that membrane called the cell wall.

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Cell Membrane

• Cell membranes regulate what enters leaves a
  cell.
• They also aid in protection support.
• Nearly all cell membranes are a flexible, double
  layered sheet called a lipid bilayer.
• P. 182, fig. 7-12

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• Along w/ lipids, the cell membrane also has
  proteins carbohydrates embedded in it.
• The lipid bilayer is often called a mosaic, b/c
  it is made up of many different parts.

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• The proteins form channels pumps for moving
  materials across the membrane.
• The carbohydrates act like ID cards, allowing
  individual cells to identify one another.

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• http//www.youtube.com/watch?vQqsf_UJcfBcfeature
  related
• http//www.youtube.com/watch?vvh5dhjXzbXc

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Cell Walls (CWs)

• Found in
• Plants
• Algae (Protists)
• Fungi
• Many prokaryotes (not all)
• CWs lie outside the cell membrane.

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• Most cell walls allow certain substances to pass
  through.
• Such as
• H20
• CO2
• O2
• Its main function is to support protect the
  cell.

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• Most CWs are made of fibers of carbohydrate
  protein.
• Plant CWs are made of cellulose.
• Cellulose is a tough carbohydrate fiber.
• The fiber in your diet.

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Diffusion Through Cell Boundaries

• The movement of molecules from one side of the
  cell membrane to the other.

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Measuring Concentration

• Recall what a solution is.
• Whats a solute?
• Whats a solvent?
• Concentration the mass of solute in a given
  volume of solution, or mass/volume.
• Lets figure concentration of a solution.
• If you dissolved 12g of salt in 3L of water, the
  concentration would be 12g/3L 4 g/L

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Diffusion

• Diffusion process of molecules moving from an
  area of high concentration to an area of low
  concentration.
• Equilibrium when the concentration of a solute
  is the same throughout a solution.
• Diffusion will go on until EQ is reached.

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• What does diffusion have to do w/ a cell
  membrane?
• P. 184, fig. 7-14
• Diffusion requires no E output by the cell.
• Its free!

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Osmosis

• Biological membranes are selectively permeable.
• Some substances can pass some cant.
• Water passes very easily.
• However, many solutes cant.
• Osmosis the diffusion of water through a
  selectively permeable membrane.

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How Osmosis Works

• H2O moves from an area of high H2O concentration
  to an area of low H2O concentration.
• Water moves across the membrane until EQ is
  reached.

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Osmosis
Section 7-3
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• http//www.youtube.com/watch?vsdiJtDRJQEcfeature
  related

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3 types of Osmotic SolutionsP. 186, fig. 7-16

• Isotonic
• Concentrations are equal on both sides of the
  membrane.
• Normal looking cells
• Hypertonic
• Solution outside the cell has a higher solute
  concentration than the inside of the cell.
• Water leaves the cell.
• Cells shrink
• Hypotonic
• Solution has a lower solute concentration than
  the cell.
• Water enters the cell.
• Cells swell

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Plant Cells
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Plant Cells

• http//www.youtube.com/watch?vGOxouJUtEhEfeature
  related

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Turgid
Flaccid
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Red Blood Cells
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Osmotic Pressure

• Osmosis exerts a pressure known as osmotic
  pressure.
• Osmotic pressure -the pressure exerted by the
  flow of water through a semi permeable membrane.
• This can cause serious problems for a cell.
• Cells can swell to the point of bursting.

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• Fortunately, animal cells are in a isotonic
  solution dont come into contact w/ pure H2O.
• If they did they would burst.
• Also, plant cells bacterial cells have cell
  walls that prevent the cell from bursting.

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Facilitated Diffusion

• Facilitated diffusion movement of specific
  molecules across CMs via protein channels.
• P. 187, fig. 7-17
• There are hundreds of protein channels that allow
  only certain substances to cross different
  membranes.

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• This process does not require E.
• It acts just as diffusion.
• It goes from high to low concentrations.

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Facilitated Diffusion

• http//www.d.umn.edu/sdowning/Membranes/diffusion
  animation.html

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Active Transport

• When cells move materials against the
  concentration gradient, they are using Active
  Transport.
• This process requires E.
• Active transport is carried out by transport
  proteins or pumps found in the membrane.

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• Transport of larger molecules can be done through
  2 active transport processes
• Endocytosis
• P. 188, fig. 7-18
• Exocytosis
• For each of these processes, the shape of the
  membrane changes.

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Endo Exo

• http//www.youtube.com/watch?vK7yku3sa4Y8feature
  related

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Molecular Transport

• Endocytosis process of taking material into the
  cell by infolding or pocketing of the CM.
• This process forms a vacuole in the cell.
• This process works for
• taking in food
• larger molecules
• other cells
• 2 examples of endocytosis are
• Phagocytosis
• Pinocytosis

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• Phagocytosis extensions of cytoplasm surround a
  particle package it w/in food vesicles.
• Amoebas use this method
• Fig. 7-18

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• Pinocytosis the process of taking in liquids
  from the surrounding env.

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• Many cells also release large amounts of material
  from the cell.
• This process is called exocytosis.
• Ex
• The removal of water by a contractile vacuole is
  an example of this kind of active transport.

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• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter6/animations.html

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Section 7-4

• The Diversity of Cellular Life

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Unicellular Organisms

• Unicellular orgs. made of one cell.
• Unicellular orgs. can
• grow
• respond to the env.
• reproduce
• transform E

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• Unicellular orgs. dominate life on Earth.
• Examples on P. 190, fig. 7-20

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Multicellular Organisms

• Orgs. made up of many cells.
• Multicellular orgs. have cells that are
  specialized.
• Cell Specialization process in which cells
  develop in different ways to perform different
  tasks.
• P. 191, fig. 7-21

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Specialized Animal Cells

• Examples of specialized cells in animals
• Red blood cells
• Transport O2 throughout the body.
• Pancreatic cells
• Produce enzymes that aid in digestion.
• Contain cells specialized for making proteins.
• These cells have numerous ribosomes.
• Muscle cells
• Able to contract relax, causing movement of our
  bones.

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Specialized Plant Cells

• Guard cells of the stomata
• Monitor a plants internal conditions, makes
  changes accordingly.

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Levels of Organization

• The levels of organization in a multicellular
  org. are as follows
• Individual Cells
• Tissues
• Organs
• Organ systems
• Organism
• P. 192, fig. 7-22

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Examples

• neurons (nerve cells)
• nervous tissue
• brain
• central nervous system
• human

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• Tissue a group of similar cells that perform a
  specific function.
• Ex
• The collection of cells in the pancreas that make
  proteins.
• Most animals have 4 types of tx
• Muscle
• Epithelial
• Nervous
• connective

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• Organs many groups of txs working together.
• Each muscle is an organ.
• However, it also contains nervous tx,
  connective tx.

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• Organ system a group of organs working together
  to perform a specific function.
• Digestive system
• Reproductive system
• Nervous system
• Altogether, organ systems make up the organism.

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Body Systems