Download Honors Biology Name Cells Notes, continued… PROKARYOTIC

Honors Biology
Name
Cells Notes, continued…
PROKARYOTIC AND EUKARYOTIC CELLS
Cells either be divided into one of two major categories. Cells can be
A. PROKARYOTIC
includes: domains Bacteria & Archaea
or
B. EUKARYOTIC
includes: 1. protists
2. fungi
3. plants
4. animals
Structural Differences
Prokaryotic
Eukaryotic
1.___no nucleus_________________________ 1._nucleus present______________________
2.___unicellular_________________________ 2._uni or multicellular __________________
3.___no membrane bound organelles________ 3._have membrane bound organelles___________
4.__smaller, simpler (1 – 10 microns)_________ 4.__larger, more complex (>10 microns)
5. 1 circular chromosome, maybe plasmid
5. Several to many linear chromosomes
Structural Similarities
1. plasma membrane (cell membrane)
2. cytosol (cytoplasm) – gel like fluid with variety of solutes in water (ions, sugars, nucleotides, etc)
3. have ribosomes (prok are smaller)
4. have DNA and RNA (universal genetic code system)
5. may have flagella (slight differences prok/euk structure)
6. all prok have cell walls (not cellulose – use proteins/other carbs); SOME euk have cell walls (fungi – chitin, plants –
cellulose – some protists – cellulose)
Look at the illustrations of these two different types of cells and notice the differences and similarities.
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EUKARYOTIC CELL STRUCTURE
Plasma Membrane (cell membrane)
***WITHOUT A PLASMA MEMBRANE THERE WOULD BE NO DISTINCT CELL STRUCTURE!!!***
1. Function
1. Selectively (Semi) Permeable – allows only certain substances to enter/leave
2. Surrounds and Protects the cell contents. Separates one cell from another and from the environment.
Other functions of the cell membrane will be discussed under structure.
2. Structure.
1. Lipid bilayer (2 layers of phospholipids)
*Cholesterol is found in the membrane of animal cells only*
2. Proteins are embedded within the bilayer. Some go all the way through and some are just on periphery/partly
embedded.
The proteins in the membrane can have various functions. Some of these are:
a. Receptors- receive messages from the outside of the cell and then send the message to the cell interior. Hormones
or other molecules are the messenger molecules that bind the receptor. Both receptor/messenger molecules are
involved in cell-to-cell communication.
b. Channels (or transport)- allow philic substances (polar/ionic) to pass into or out of the cell
c. Enzymes – many reactions occur ON (or near) cell membrane
Three important factors that determine where molecules will pass across the membrane, either into or out of the cell, are
polarity, charge and size. Decide where the following five substances will pass, and why.*We will do this chart in class
Philic
Phobic
Philic
Where it passes through
Polar
Nonpolar
Charged
Bilayer
Protein Pore
Water
Fatty acids
Glucose
Amino Acids
Ions
Steroids
Note: Most molecules other than lipids will need to move through protein channels in order to pass across the membrane.
Even though water can pass across the bilayer because it is a very small molecule, most water passes through channels
called aquaporins.
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NOTE: There are other cell membranes in addition to the plasma membrane. These membranes surround or are a part of
many cell organelles. The structure of these membranes is similar to that of the plasma membrane. All of these membranes
are semipermeable, but the specific function will change from organelle to organelle. The reason the function changes is
because the types and amounts of proteins and phospholipids within the membrane will vary.
NOTE: Since prokaryotic cells do not have any intracellular membranes, they must use their plasma membrane for any
chemical reactions that require a membrane surface. An example would be the chemical reactions of cell respiration that
occur on the mitochondrial cristae membrane of eukaryotes must occur on the plasma membrane of some prokaryotes
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Cell Communication
Messenger molecules like hormones can be secreted from 1 cell into
the body and travel to other cell via the blood stream. Messenger
molecules allow cells to communicate with each other. In this
diagram the hormone is “telling” cell 2 to produce a new protein
Cells communicate with each other by way of hormones or other messenger
molecules binding to receptors of other cells
Steps of cellular communication
1. Hormone binds to receptor (on
cell 2) and the receptor changes
shape (shown as 1).
2. Receptor with new shape can
now bind to another protein (2) it
couldn’t bind to before.
3. The #2 protein then changes
shape and can bind to #3 protein
that it couldn’t bind before.
4. This domino effect continues
until a transcription factor (TF)
changes shape and can bind to the
promoter of a specific gene.
5. The gene is then transcribed by
RNA polymerase and translation
will produce the new protein.
The new protein can then change
the function of cell 2 in some way
(Ex: enzyme) or it can be secreted
from cell 2 and carry a message to
another cell. (Ex: pancreas cell
produces and secretes insulin)
Note: This is just one example of how transcription factors get activated so
they can turn on genes. Sometimes the signal or message does not have to
come from outside the cell, it can come from inside the cell.
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Cell Wall
A. Structure and Function
1. _Outer boundary – outside the plasma membrane
2. _Supports and protects the cell, gives it structure
Organisms that contain cell walls:
Plants/Protists (algae) – cellulose (polysaccharide)
Fungi – chitin (polysaccharide)
Bacteria – peptidoglycan (a polymer of sugars and amino acids)
Cytoplasm
A. Structure
1. CYTOSOL: Semi-liquid gel like material, mostly water with dissolved chemicals like a) nutrients (sugar), salts,
minearls, vitamins and b) wastes
2. Contains all organelles and structures between the Cell Membrane and the Nuclear Membrane
B. Function
1. Site of many chemical reactions (has substrates/enzymes for reactions)
2. Constantly in motion due to cytoplasmic streaming facilitated by the cytoskeleton. Aids in movement of materials
in the cell for more efficient function.
Microfilaments and Microtubules (microtubules make up centrioles, flagella, cilia, spindle fibers … Cytoskeleton
contain both microfilaments and microtubules )
Microfilaments:
1. Slender protein filaments found in the cytoplasm
2. Have the ability to move, can cause movement of cell and cell structures.
Microtubules:
1. Helps to give the cell an internal structure, Also have the ability to move and aid in movement of the cell/cell
structures
2. Long, hollow tubular structures composed of protein.
Many cell structures are made from microfilaments and microtubules. One of them is the cytoskeleton that we will
examine now. The other structures we will look at later in the unit.
Cytoskeleton
A. Structure
1. A network of microfilaments and microtubules that extent throughout the cytoplasm from PM to PM. (connected to
membrane)
2. Flexible NOT rigid. Dynamic structure that is constantly assembled and disassembled depending on cell needs.
B. Function
1. Gives cell its shape, help suspend organelles in the cell.
2. Aids in movement of cytoplasm/ Moves cell structures like chloroplasts and secretory vesicles. Aids in whole cell
movement of amoeba or WBC.
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Nucleus
A. Structure
1. Surrounded by a double membrane – TWO phospholipid bilayers – Called a nuclear envelope. The outer membrane
is often continuous with the RER.
2. Membrane has pores surrounded by proteins which allow mRNA, tRNA, units of ribosomes and other large
molecules to pass.
3. Contains DNA (normally in chromatin form) plus nucleolar regions.
4. Nucleolus: the nucleolar region is a densely clustered region of chromatin from several different chromosomes.
These genes code for rRNA. It is the site in the cell where rRNA and protein come together to form the large and
small subunits of the ribosomes. Cell has 1 or more nucleoli.
B. Function
1. Controls all cell functions because it contains the gene segments that code
for proteins that are responsible for the cell’s structure & function.
2. Location of RNA synthesis (transcription): mRNA, tRNA and rRNA for
synthesis of cellular proteins.
Endoplasmic Reticulum (ER)
A. Structure
1. Tube-like channels and flattened sacs composed of a single membrane (bilayer) lipids & proteins. Extends
throughout the cell.
2. Interior space (lumen) is fluid filled and contains enzymes & proteins needed for reactions
B. General Functions
1. Transports molecules (proteins) to different parts of the cell
2. Provides a high surface area for reactions to take place. Also, an internal space (lumen) for reactions
3. Transport vesicles pinch or bud off from the ER to move materials throughout the cell.
Specific Functions of the RER and SER
RER 1Rough ER- membrane contains ribosomes that synthesize proteins to be sent to the Golgi.
2 site (lumen) where proteins produced can be modified
SER 1Smooth ER – no ribosomes, continuous with RER
2Site of protein modification, Site of synthesis of lipids, site of detoxification of harmful substances. (SER
contains the enzymes needed for these reactions to occur)
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Vesicle
A. Structure
1. Small membrane sac that is produced by pinching or budding off membranes from the golgi or ER
B. Function
1. Varies – carries different materials throughout the cell OR can store cellular materials
Ribosomes
A. Structure
1. Small organelle- NOT SURROUNDED BY MEMBRANE. Made up of a large and small subunit that join during
translation.
2. Made of rRNA and proteins, assembled from genes in the nucleolus.
B. Function
1. site of translation of genetic information into proteins
Ribosomes can be found either:
a. Freely floating in the cytoplasm
b. bound in the RER
(both are structurally identical and interchangeable)
Some proteins need to be translated on free ribosomes, and some need to be translated on bound ribosomes. The
differences will be discussed later.
Ribosome Production
In order to produce a ribosome you need to produce rRNA and ribosomal proteins.
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rRNA is transcribed from genes in the nucleolus region of the nucleus.
mRNA that codes for the ribosomal proteins is transcribed from genes on chromatin outside of the nucleolus.
The mRNA travels out of a nuclear pore and binds to a small ribosomal subunit. The large subunit joins and the
protein is translated.
The ribosomal proteins travel into the nucleus and will combine with the rRNA in the nucleolus region to form
the separate ribosomal subunits.
The separate ribosomal subunits will then travel out of the nuclear pores into the cytoplasm. They will only
come together to form a complete ribosome when an mRNA attaches for translation. Otherwise they float
around as separate subunits.
Anytime you see a complete ribosome (both subunits together), it is in the process of translation.
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Ribosome Production diagram
True or False? “You need a ribosome to make a ribosome”. Explain your answer.
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Golgi Apparatus (Golgi Bodies)
A. Structure
1. Stacks of flattened, pita-like sacs made of membrane (containing
many enzymes)
B. Function
1. Process and refine proteins that were synthesized on ribosomes
attached to the RER. Proteins are transported to the Golgi as shown
below.
2. Package refined proteins in vesicles that transport the proteins to
different destinations based on the proteins functions
a. Secretory Protein – (hormones like Insulin) packaged in secretory vesicle that fuses with cell membrane
b. Lysosomes – enzymes for hydrolysis are packaged in a vesicle that remains in the cytoplasm.
c. Membrane Proteins- membrane proteins needed for organelles or plasma membrane may be formed in the
membrane of the ER. They bud off and travel to the Golgi where they are formed into a vesicle that can fuse with an
organelle or PM and become part of the membrane. If a protein is NOT embedded in the vesicle membrane, but is on
the interior of the vesicle it can be deposited within the interior of an organelle when the vesicle fuses with it.
Lysosomes
A. Structure
1. Small, membrane bound organelles that contain many hydrolytic (digestive) enzymes, (they hydrolyze proteins,
lipids, carbs, n. acids) Form as vesicles that bud off the golgi,
Enzymes in the lysosome require an acidic pH (~5) for optimal activity. The membrane of the lysosome helps to
provide a separate, optimal environment for the enzymes and protects the contents of the cytoplasm from the
enzymes’ action.
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B. Function
1. Fuse with food vesicles formed when the cell engulfed food or a foreign substance (white blood cells engulfing
bacteria) After fusing, enzymes hydrolyze food/substance. Single-celled protozoans like Amoeba and Paramecium
white blood cells, products of hydrolysis are used by the cell.
2. Can fuse with worn out organelles and break them down. Products of the breakdown may be recycled and used
again by the cell.
3. _Programmed destruction of cells in an organism can occur when lysosomes break open. This occurs during
developmental changes like metamorphosis of frog & breakdown of webbing between fingers/toes of human fetus.
Cells that contain lysosomes
a. Animal Cells
b. Some animal-like protists (protozoans)
Tay-Sachs Disease
Occurs when a person has a genetic mutation that prevents them from producing an important lysosomal
enzyme that degrades lipids. These lipids accumulate in the brain tissue and cause death in the early years
of life.
Proteins produced at the free floating ribosomes and those produced at the ribosomes on the RER have different
functions. The following diagram shows how the various organelles of the cell function together. This example shows
how cells produce proteins that need to be secreted out of the cell (secretory proteins). It will include coding of,
production, refinement, packaging, and transport of a secretory protein.
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ENDOMEMBRANE SYSTEM OF A EUKARYOTIC CELL
Note: Notice the relationship among the different membranes within the cell. Although each membrane has a unique
arrangement of lipids and proteins to suit its function, these membranes are related through direct physical contact, or
through the transfer of membrane-bound vesicles. The latter occurs by the pinching off (budding) of a section of
membrane (vesicle), and its later fusing with the membrane of another organelle, or the plasma membrane. Membrane
structures can fuse with each other because they are made of similar material.
Big picture found on the next page…
Steps in the Production, Modification, Transport, and Sorting of a Secretory Protein
1. Transcription of mRNA in the nucleus. Ribosomes produced in nucleolus, migrate to RER (ribosome
receptor proteins on membrane of RER).
2. Translation of polypeptide at the ribosome on the RER.
3. Polypeptide moves into lumen of RER. Enzymes in the lumen of the RER modify/ refine the polypeptide:
Some amino acids(s) removed (ex: methionine); Sometimes sugar added to make glycoprotein; Tertiary or
quaternary structure established.
4. Modified polypeptide transported through the lumen of ER.
5. ER membrane pinches or buds off into a transport vesicle. A transport vesicle is just a part of the ER
membrane surrounding the protein. The vesicle is now carried by the cytoskeleton through the cytoplasm to the
Golgi complex.
6. The vesicle fuses with the membrane of the Golgi stack.
7. Enzymes in the Golgi modify the proteins further. Final refinement occurs here. Some sugars are removed,
proteins are further modified, sorted into different batches depending on their destinations, and packaged into
vesicles.
8. Proteins move in vesicles from one stack to the next for more modification.
9. Final sorting and packaging of proteins into vesicles so they can move to their final destinations (proteins
are sorted and batched together for their correct destination)
10. Vesicle buds off the Golgi and travels to the cell membrane.
11. The vesicle fuses to the cell membrane and releases the protein into the intercellular fluid (exocytosis!).
12. Protein travels through the bloodstream to other body cells where they are needed.
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****WE WILL DO THIS DIAGRAM IN CLASS TOGETHER!!***
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Differences between the production of a secretory protein, lysosomal enzymes, and membrane proteins such as
receptors or channels on the plasma membrane or on organelle membranes
Proteins produced at ribosomes on the rough ER and Golgi
Secretory, lysosomal enzymes, and membrane proteins are produced by the following steps because they are
usually used in cells other than those in which they are produced.
• Translated on the ribosomes, modified on the rough ER and Golgi
• Secretory proteins (messenger molecules, antibodies)
• Lysosomal enzymes
• Membrane proteins (channel proteins, enzymes, receptors)
Proteins produced at free floating ribosomes
The proteins produced at free floating ribosomes are modified in the cytoplasm and are primarily used right in
the cell in which they are produced.
• Translated on free floating ribosomes, modified by enzymes in the cytosol
• RNA polymerase, DNA polymerase
• Transcription factors
• Proteins in microtubules and microfilaments
These are the 3 possible products of the EMS (Endomembrane system) of the cell:
***WE WILL DO THESE DRAWINGS IN CLASS****
1. Secretory Protein ex) insulin, growth hormone, adrenalin (=messenger molecules, i.e. hormones) – meant to be
secreted, travel to other cells.
2. Lysosomal Enzyme ex) lipases, proteases, sucrases, nucleases, maltase – digestive enzymes in lysosome for use inside
cell
3. Membrane-bound Protein proteins that must be embedded in a lipid bilayer. Ex) transport proteins, channel proteins,
enzymes, receptor proteins
Notice that all of these proteins are produced on ribosomes that are attached to the ER. This is because they need to be
inside a vesicle, or part of a vesicle membrane at some point in their production. Proteins that are produced on free
ribosomes are usually proteins that are needed within the cytoplasm of the cell. Examples of these types of proteins would
be: cytoplasmic enzymes, and proteins making up microtubules and microfilaments, nuclear enzymes, ribosomal proteins
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***WE WILL DO THIS DRAWING IN CLASS****
Mitochondria
A. Structure
1. Oval shaped organelle with a double membrane
2. Has an inner membrane called the cristae membrane. The cristae is folded many times to increase surface area for
the enzymes needed for C/R. Many of the reactions of C/R take place at the cristae.
3. Inner fluid filled space is called the matrix (meaning background substance). Reactions of C/R can take place here
too.
4. Contains its own DNA (small, circular pieces like plasmids); also contains ribosomes in the matrix (protein
synthesis to occur)
B. Function
1. Site of Cellular Respiration (C/R) where glucose is broken down in the presence of Oxygen in order to produce
usable cell energy in the form of ATP
2. C6H12O6 + 6O2  6CO2 + 6 H2O
Because of their function, mitochondria are often referred to as the “power houses” of the cell. Most eukaryotic
cells contain mitochondria, but they are especially abundant in animal muscle and liver cells.
Remember that plant cells also contain mitochondria, in addition to chloroplasts. These two organelles have
totally different functions. Many students confuse this issue and think that only animal cells contain mitochondria,
while plant cells contain only chloroplasts.
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Chloroplasts
A. Structure
1. Double Membrane bound organelle.
2. Contain tiny disc shaped vesicles called thylakoids. The thylakoids contain the chlorophyll pigment which makes
the organelle green. In addition to other molecules important in P/S. Chlorophyll is the molecule that absorbs the
light.
3. Grana = a stack of thylakoids
4, Stroma – liquid inside the chloroplast surrounding the thylakoids
B. Function
1. The site of Photosynthesis (P/S) in autotrophic organisms
2. Light energy is converted into chemical energy of glucose. The reactions of P/S take place within the thylakoid
membrane and in the stroma.
3. 6CO2 + 6 H2O  C6H12O6 + 6O2
Refer to page 334 in your textbook OR the four slide PPT
The Endosymbiosis Hypothesis
The Endosymbiosis Hypothesis helps to explain how eukaryotic organisms with many organelles may have evolved from
less complex prokaryotes. Specifically, it helps to explain how mitochondria and chloroplasts may have evolved. It is
believed that these structures were once free-living prokaryotes that were engulfed by other prokaryotes, and eventually
became unable to live independently. They entered a symbiotic relationship with the organism that engulfed them.
Mitochondria were probably aerobic prokaryotes that later became organelles that were responsible for aerobic respiration
within a larger organism, while chloroplasts were probably photosynthetic prokaryotes that later became organelles
responsible for photosynthesis.
Theory –
Prokaryotic internal parasite or nondigested organism evolved to present day
mito/chloroplast.
All eukaryotic cells have mitochondria, only
some with chloroplast … so mitochondria
evolved first.
Evidence for the Endosymbiosis Hypothesis
Mitochondria and chloroplasts:
1. Contain genes that code for SOME enzymes needed in their
functions.
2. Contain smaller, bacterial-like ribosomes
3. Reproduce by a process similar to binary fission in bacteria
4. Composed of a double membrane (due to engulfing)
5. Size is comparable to bacteria
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A plastid is a type of organelle bound by a double-membrane that is found in plant cells. A chloroplast is one type of
plastid, but there are several others.
Plastids other than chloroplasts:
1. Leucoplast place where starch is stored for the plant. (many in potato!)
2. Chromoplast stores many pigments  responsible for making colors of flowers and some leaves.
Vacuoles
A. Structure
1. Fluid filled sac made of membrane-similar to vesicles.
B. Function
1. Like vesicles, they have varied functions
Vacuoles can be found in many different organisms, where they have varied functions.
a. Central vacuole in plants Stores H2O, pigments, wastes, and other molecules. Plant cells grow in size by taking
up water into its vacuoles. Eventually smaller vacuoles fuse to form one large, central vacuoles
b. food vacuole in protists Food istaken in and a membrane folds around it to form a food vacuole. May
fuse with lysosome for digestion.
c. contractile vacuole in protists pumps out excess water that is constantly entering the cell. Otherwise the
cell would swell and burst
Paramecium: are fresh-water
protists. The concentration of
water in their environment is VERY
HIGH. As such, it tends to move
into the body of the paramecium,
where the concentration of water
is LOWER. This is natural diffusion
of water from [high]  [low]
Cilia and Flagella
A. Structure
1. Extension of the plasma membrane. The inside of these structures contain a 9 + 2 (9 sets of two, plus two in the
center) organization of microtubules responsible for movement
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B. Function
1. They whip back & forth causing the cell to move. Sometimes they function to move materials over the cell.
Differences between cilia and flagella:
Cilia
shorter than flagella and many present
on one cell
Cilia are found:
1. human respiratory tract
Mucus is moved up & out of resp tract
2. Paramecium
help to move food into the organism
and help to move the entire organism
Flagella
long and only 1 or a few present per cell
Flagella are found:
1. sperm cells - movement
2. Some protists – for movement
3. Some bacteria (slightly different structure in prok cells)
Note that centrioles are only found in
Centrioles
animal cells.
A. Structure
1. small pair of organelles found outside the nucleus at right angles to each other. Composed of microtubules in a
slightly different arrangement (9 sets of 3) compared to cilia and flagella.
B. Function
1. Found only in animal cells – may play some role in cell division (function isn’t well understood)
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COMPARISON OF CELLULAR STRUCTURES *We will do this together in class*
STRUCTURE
Prokaryotes
Protists
Fungi
Plants
Animals
Cell Wall
Cell Membrane
Cytoplasm
Vacuoles
Chloroplasts
Centrioles
Nuclear
Membrane
Nucleolus
Chromosomes
Ribosomes
Mitochondria
ER
Golgi Apparatus
Lysosomes
Microtubules
Cytoskeleton
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How Cells Are Studied
1. Microscopes
A. Compound Light Microscope _Uses a combination of lenses (objective and ocular), can see live
specimens in color. Sample must be thin enough for light to pass through it on the slide. Relatively
inexpensive and easy to use.
Light microscopes use light and class lenses to magnify the image. Although they are very important tools that
are necessary to study cellular structure, they can only magnify the image clearly up to about 2000X. If you
want to study cell structure in more detail you must use an electron microscope. This type of microscope uses
electrons instead of light and magnetic lenses instead of glass and can therefore increase the magnification and
clarity of the image.
B. Transmission Electron Microscope (TEM) – 2D image, gives greatest magnification, can see
interior detail of the cell.
C. Scanning Electron Microscope (SEM) 3D image, see surface features of the cell.
Micrograph
Microscopes are used to study the stricter of cells, but if you want to learn about the function of the various cell
organelles you have to study their biochemistry and metabolism. In order to do this you must first isolate the
organelles from each other in a process known as cell fractionation
2. Cell Fractionation – Process used to separate different cell parts so their specific functions can be studied.
1. Break open cells – allow contents to spill out
2. Spin in centrifuge at different speeds to allow different cell structures to settle out according to size
(largest first)
3. Collect isolated cell parts and study their functions.
Cell Fractionation Animation http://www.sumanasinc.com/webcontent/animations/content/cellfractionation.html
Virtual Microscopy http://micro.magnet.fsu.edu/primer/virtual/virtual.html
University of Delaware Virtual Microscope https://www.udel.edu/biology/ketcham/microscope/
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