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8/7/2019 Cell Structure Index Cards
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Erick Camacho CellStructure
Cell theory: the basic unit of structure
and function of all living organisms is the cell.
Virchows Theory (1855): all cells
arise from pre-existing cells by cell division.
Partially Permeable: refers to the
thin membrane surrounding all cells and
controls the exchange between the cell andits environment; allows a controlled traffic of
materials across it in both directions.
Light Microscope: uses light as a
source of radiation
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Electron Microscope: uses electrons
as a source of radiation.
Ultrastructure: the fine or detailed
structure of a cell as revealed by the electron
microscope.
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Similar Features of Plant and Different Features of Plant
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Animal Cells
Each cell is surrounded by aplasma membrane.
Each cell has a nucleus.Each cell has a mass of looselycoiled threads known aschromatin.
Both contain nucleolus, which ismade of loops of DNA fromseveral chromosomes.
Both contain cytoplasm, which isan aqueous material, varying inconsistency.
Both contain organelles, whichare defined as functionally andstructurally distinct parts of a cell.
Both contain mitochondria, which
specialize in aerobic respiration.Both contain the Golgi apparatus,which is part of a complex internal
and Animal Cells
The animal cell contains thecentriole, which specializes in
nuclear division. The plant cells are generallarger and are surrounded by acell wall outside the plasmamembrane.
The plant cell containsplasmodesmata, which links
neighboring plant cells.The plant cells also contain alarge central vacuole andchloroplasts.
Plant cells also contain thetonoplast, which control theexchange between the vacuole
and the cytoplasm.
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sorting and distribution systemwithin the cell.
Nucleus: the largest cell organelle;
surrounded by two membranes known as the
nuclear envelope.
Centrioles: a hollow cylinder about
0.4 m long, formed from a ring of
microtubules.
oThese microtubules are used to grow the spindle
fibers for nuclear division.
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Golgi Apparatus: a stack of flattened sacs. This
stack is constantly being formed at one end from
vesicles which bud off from the ER, and broken down atthe other end to form Golgi Vesicles.
o The apparatus collects, processes and sorts
molecules, read for transport in Golgi Vesicles
either to other parts of the cell or out of the cell.
oGolgi Vesicles are also used to make lysosomes.
Ribosomes: the components of cells that
make proteins from all amino acids.
Lysosomes: spherical sacs, surrounded by a single
membrane and having no internal structure.
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o They contain hydrolytic enzymes which must be
kept separate from the rest of the cell to prevent
damage.
o They are responsible for the breakdown of
unwanted structures.
Mitochondria: bean-shaped with inner membrane.
They break down sugar molecules into energy. Theirmain function is to carry out the later stages of aerobic
respiration, and as a result they make ATP, which is the
universal energy carrier in cells.
Endoplasmic Reticulum: there are two types ofEndoplasmic Reticulum:
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oRough ER: where the ER is covered by ribosomes;
transports the proteins throughout the cell.
oSmooth ER : lacks ribosomes and appears
smooth; synthesizes lipids and steroids,
metabolizes carbohydrates and steroids, and
regulates calcium concentration
Plasma membrane: separates the interior of allcells from the outside environment. The cell membrane
is selectively-permeable to ions and organic molecules
and controls the movement of substances in and out of
cells.
Cilia: long, thin extensions that can move in a
wave-like manner.
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o A few of these extensions are called flagella.
o If there are many of them and they are relatively
short then they are known as cilia.
Eye-piece graticule: a transparent
scale, usually with 100 divisions, placed withthe object on the microscope eyepiece so
that it can be seen at the same time as the
object and be measured.
Stage micrometer: used to calibrate
the eye-piece graticule.
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Magnification: the number of times larger an
image is compared with the real size of the object.
oMagnification =
Resolution: defined as the ability to
distinguish between two separate points.
Electromagnetic Spectrum: the
range of different wavelengths.
oThe longer the electromagnetic waves, the lower
their frequency.
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oWavelengths change with energy: the greater the
energy, the shorter the wavelength.
The limit of resolution is about one
half the wavelength of the radiation
used to view the specimen.
The electron microscope is used mainly
because electrons are negatively chargedparticles and free electrons behave like
electromagnetic wavelength.
They are a very suitable form of
radiation for microscopy because
o their wavelength is extremely short
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o they are negatively charged particles, which
means that they can be focused easily using
electromagnets.
There are two types of electron
microscopes:
oThe TEM (transmission electron microscope): the
beam of electrons is passed through the specimenbefore being viewed.
o The SEM (scanning electron microscope): the
electron beam is used to scan the surfaces of
strictures and only the reflected beam is observed.
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The one disadvantage of using a SEM is that it
cannot achieve the same resolution as a transmission
electron microscope.
Prokaryotes: organisms that lack nuclei.
o
Prokaryotes are referred to as bacteria.
Eukaryotes: organisms whose cells
possess nuclei.
o Eukaryotes are referred to as animals, plants,
fungi etc.
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Specialized cells show division of labor
by being grouped into tissues. The tissues are
then further grouped into organs and the
organs into systems.
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Tissue: a collection of cells, together
with any intercellular secretion produced by
them, that is specialized to perform one ormore particular functions.
oThe study of tissues is called histology.
Organ: part of the body which forms a structural
and functional unit and is composed of more than onetissue.
System: a collection or organs with a particular
function.
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