Chapter 4
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All living organisms are made up of cells
Cells are the basic units of structure and
function in living organisms.
All cells come from cells that existed before
them by cellular reproduction.
Schwann, Schleiden and Virchow are credited
with coming up with the basics of the cell
theory
http://www.youtube.com/watch?v=dscY_2QQbKU
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Every cell has the following main
characteristics:
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Plasma membrane covering
Cytoplasm
Their genes are made of DNA
Ribosomes are tiny organelles that assemble
proteins
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Antone von Leeuwenhoek assembled the first
microscope that was useful for scientific
research.
Compound light microscopes reflect light
through a set of lenses and the specimen to
magnify the specimen.
See handout for the parts of the microscope – you must know it.
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Two important characteristics that determine
the quality of a light microscope:
◦ Magnification – an increase in the apparent size of
an object. We calculate magnification by the
following:
Magnification of eyepiece x magnification of
objective = total magnifying power
• Resolution – the measure of clarity of an image. As
the magnification increases, the resolution of the
image decreases.
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Some microscopes use beams of electrons for
magnification instead of light – electron
microscopes
Scanning electron microscope (SEM) – used to
study the detailed architecture of the surface
of the object. Forms a 3D image, but does
not show the inside of the object.
Transmission electron microscope (TEM) –
used to provide a detailed 2D image of the
inside structure of the object that is viewed.
•http://micro.magnet.fsu.edu/primer/java/el
ectronmicroscopy/magnify1/index.html
•http://www5.pbrc.hawaii.edu/microangela/i
ndex.html
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http://www.cellsalive.com/howbig.htm
Cells are microscopic, they are visible only
with light microscopes. Most of their size
ranges from 1-100 µm.
The cells are small, because they have to be
able to carry materials from one side of the
cell to the next in a short period of time.
Cells must have a large enough surface area
to be able to take in nutrients and oxygen
and release waste quickly.
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Prokaryotic cells – small cells (about 1-10
µm) that do not have a nucleus and
organelles that are covered with membranes
Prokaryotic cells are found in Bacteria and
Archaea (two main domains of life).
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Nucleoid region – part of the prokaryotic cell
where the DNA is found
Cell membrane – innermost covering of the
cell
Cell wall – made up of a special mix of
polysaccharides and proteins (antibiotics
break it down)
Capsule – outside of the cell wall, protective
covering (not all bacteria have it)
Flagella (sing. Flagellum) – moves bacteria
Pili – used to stick them to surfaces and for
conjugation (exchange of genetic materials
between bacteria)
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Cytoplasm – dissolves substances and holds
organelles
Ribosomes – organelles that make proteins in
the cytoplasm
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http://www.ted.com/talks/lang/eng/bonnie_bassler_on_how_bacteria_communicate.html
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http://www.youtube.com/watch?v=RGfs328X8Kw – artificial bacteria
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http://www.youtube.com/watch?v=tqOVYpkZ0qs – bacteria song
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Protists, Fungi, Plants, and Animals
Have nucleus and organelles that are
surrounded by phospholipid membranes
(membrane-bound organelles)
Much larger and more complex than
prokaryotic cells. (10-100 µm)
Reproduce sexually and asexually
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http://www.youtube.com/watch?v=Y3u_GDIj7RI&feature=related
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Nucleus
◦ Control center of cell; contains most of the cell’s
DNA
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Nucleolus
◦ Location where ribosomes are synthesized, made
up of DNA, RNA and proteins
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Nuclear envelope
◦ Protects the DNA in the nucleus, nuclear pores
allow the exchange of materials.
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Amazing cells: http://learn.genetics.utah.edu/content/begin/cells/insideacell/
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Ribosomes
◦ Protein synthesis – mushroom-shaped organelle
that is made up of RNA and proteins
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Rough ER
◦ Comprised of a network of tubes and flattened
sacs.
◦ Continuous with plasma membrane and nuclear
membrane and made up of the same material
◦ Site of protein synthesis (consists of ribosomes) and
protein folding (this is where many proteins get
their secondary and tertiary structures).
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Smooth ER
◦ Site of lipid and carbohydrate metabolism
◦ No ribosomes
◦ Membrane structure, so it is also made up of
phospholipids and proteins
◦ Detoxification
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Golgi Apparatus
◦ Connected with ER; flattened disc-shaped sacs,
stacked one on top of the other
◦ Modification, storage, and packaging of proteins.
◦ “Tags” proteins so they go to the correct destination
◦ “The mailroom of the cell”
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Lysosomes (in animal cells and some protists)
◦ Digestion of nutrients, bacteria, and damaged
organelles; destruction of certain cells during
embryonic development
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Peroxisomes
◦ Diverse metabolic processes break down H ions into
hydrogen peroxide
◦ Detoxification
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Vacuoles
◦ Digestion (like lysosomes); storage of chemicals,
cell enlargement; water balance, really large in
older plant cells
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Chloroplasts
◦ Conversion of light energy to chemical energy of
sugars (site of photosynthesis)
◦ Double membrane structure
You must be able to draw and label the parts of
chloroplasts
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Mitochondria
◦ Conversion of chemical energy of food to chemical
energy – cellular respiration
◦ Bound by double membrane
You must be able to draw and label the parts of
mitochondria
http://multimedia.mcb.harvard.edu/anim_mitochondria.html
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Cytoskeleton (including cilia, flagella, and
centrioles in animal cells)
◦ Maintenance of cell shape; anchorage for
organelles; movement of organelles within cells;
cell movement; mechanical transmission of signals
from exterior of cell to interior. Cilia and flagella
move the cell or move substances on the cell.
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Cell walls (in plants, fungi, and protists)
◦ Maintenance of cell shape and skeletal support;
surface protection; binding of cells in tissues
◦ Made up of cellulose in plants, chitin in fungi and
different types of materials in prokaryotes.