1.3 Cell Structures
Essential tasks of the cell
All living cells must:
• Obtain food + energy
• Convert energy from an external source to a usable form
• Build + maintain mculs that make up cell structures
• Carry out chemical reactions
• Eliminate wastes
• Reproduce
• Keep records of how to build structures
Two Basic Cell Types
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Prokaryotic Cells
No nucleus; nucleoid
Smaller
Simple internal structure
• No membrane-bound
Organelles
Ex. Bacteria
Eukaryotic Cells
Nucleus
Larger
More complex
internal structure
Membrane bound
organelles
Ex. Plants,
animal, fungi
Cell Structures
• All cells have:
– Cell membrane
– Cytoplasm
– Cytoskeleton
Eukaryotic cells have nucleus and other
organelles!
http://www.cellsalive.com/cells/membrane.htm http://en.wikipedia.org/wiki/Cell_membrane McGraw-Hill Ryerson Biology 11
The Cell Membrane
:
• Is composed of lipids (molecules that store energy) and proteins.
• Is the outermost covering of animal cells, which gives the cells
their definite shape.
• Is a semi-permeable barrier which allows only certain molecules
to pass through.
• Contains proteins that act as pumps, enzymes, etc.
• Has the ability to connect one cell to an adjacent cell.
The “Gatekeeper”’s Function:
The cell membrane surrounds the
protoplasm of a cell and
separates the content of the
cell from the outside
environment. It provides the
shape of the cell and attaches
certain cells together to form
tissues.
The cell membrane determines what enters and exits the cell
based on what the cell needs to survive.
The membrane surrounds the entire cell which allows
nothing to get into the cell without passing through the
membrane first.
The cell membrane was discovered by Karl
Wilhelm von Nageli in 1855
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Description:
an organized structure of DNA and protein that is found in cells.
-The DNA molecule may be circular or linear, and can be composed of 10,000
to 1,000,000,000[1] nucleotides in a long chain
Chromosomes also contain DNA-bound proteins, which serve to package the
DNA and control its functions.
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Function:
Chromosomes function is to control all the activities of a living cell.
Chromosomes are essential for the process of cell division and are responsible
for the replication, division and creation of daughter cells, that contain correct
sequences of DNA and proteins.
Structure:
A molecule of DNA is a very long, coiled structure that contains many
identifiable subunits known as genes.
In prokaryotes, or cells without a nucleus, the chromosome is merely a circle
of DNA. In eukaryotes, or cells with a distinct nucleus, chromosomes are much
more complex in structure.
Facts:

Chromosomes were discovered in 1842 by Karl Wilhelm von Ngeil.
http://en.wikipedia.org/wiki/Chromosome
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Description
is the combination of DNA and other proteins that make up chromosomes.
chromatin is organized in seven progressive levels of organizational
complexity, which coils the DNA into more and more compact forms through
combination of proteins.
It is found inside the nuclear envelope of eukaryotic cells.
Function
The functions of chromatin are to package DNA into a smaller volume to fit
in the cell, to strengthen the DNA to allow mitosis and meiosis, and to
control gene expression and DNA replication.
Structure
The structure of chromatin is determined and stabilized through the
interaction of the DNA with DNA-binding proteins.
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Facts
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Chromatin was discovered by Walter Flemming in 1879.
http://en.wikipedia.org/wiki/Chromatin
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Mitachondrion
Endoplasmic reticulum
Peroxisome
Lysosome
Golgi apparatus
Vacuole
Vesicle
Non-membrane bound organelles:
ribosome
cilia
flagella
General
Information
The mitochondrion of a cell works like a
power plant. It produces adenosine
triphosphate (ATP) which the cell uses for
energy. It works a bit like our brain's
pituitary gland, as it controls cell growth,
and cell death. Depending on the
organism and type of cell, there can be
various amounts of mitochondria.
Mitochondria also contain
DNA.(deoxyribonucleic acid)
Cutaway Diagram of a
Mitochondrion
The outer membrane acts as the “skin” of the
organelle, with the inner membrane acting as a
second layer of “skin.” The matrix is the space inside
the inner membrane. Cristae is the space formed by
the infoldings of the inner membrane. There is
intermembrane space between the outer and inner
membranes.
Summary
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The mitochondria of a cell keep it
going. Without mitochondria, cells
would not live. Mitochondria are
complicated, essential organelles.
There are two types: Rough and Smooth. They are named so because one type has ribosomes
attached to it (Rough) and the other does not (Smooth). Both made of a series of membranes,
the Rough ER looks like many flattened cavities surrounding the nucleus of a cell, and the
Smooth ER appears to be many small tubes. The Smooth is outside of the Rough. The interior
of the ER is called the lumen.
The Rough ER has a variety of jobs, often depending on what type of cell it is in. It creates
membranes and secretory proteins. It is what aids in the creation of insulin in the pancreatic
cells, and antibodies in leukocytes.
The Smooth ER creates lipids and metabolizes carbohydrates. It receives proteins from the
ER and moves them to other places. In liver cells,
it makes enzymes that helps remove toxins. In the
brain it synthesizes hormones.
The shape and placement of the ER allows
transportation of membranes and such to be easier
because it is in the middle of the cell and has a large
surface area. The Endoplasmic Reticulum is
essentially a shipping department, because it
‘packages’ and transports important proteins.
http://biology.about.com/library/weekly/aa041300a.htm
Peroxisomes
Characteristics:
-Spherical shape, surrounded by
lipids and proteins, lipid plasma
bilayer membrane, and
crystalline core.
Functions:
-Peroxisomes help get rid of
toxins within the cell. –
- In plants they also assist in the
process of Photosynthesis.
-Peroxisomes also are a big part
of the cell metabolism process.
-They also help with breaking
down fats and fatty acids.
-The Peroxisomes also help with
the breakdown of alcohols in the
cell, much like a small version of
the liver but for a cell.
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Sources:
-http://en.academic.ru/pictures/enwiki/80/Peroxisome.jpg
-http://www.wisegeek.com.what-is-a-peroxisome.htm
-http://micro.magnet.fsu.edu/cells/peroxisomes/images/per
oxisomesfigure1.jpg
Peroxisomes
Structure Functions:
- The structure of the
Peroxisomes give
them the ability to
breakdown toxins and
convert them into by
products like hydrogen
peroxide or just
oxygen and water.
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- The structure also helps with the
metabolism process in the way that
it can easily take in lipids and
proteins and start the breakdown
into energy that the sell uses
• Extra Info:
• -Peroxisomes have the ability to
break into another peroxisome if the
cell needs another, much like DNA
Ribosome
Description
Ribosome's are made from complexes of RNAs and proteins. It is divided
into two subunits. One subunit is larger than the other.
The ribosome makes proteins from all amino acids. The ribosome reads the
information in the RNA and uses it to create proteins. This process is known
as translation. The smaller subunit binds to the mRNA while the larger
subunit binds to the tRNA and the amino acids. The ribosome finishes
reading a mRNA and then the two subunits split apart.
The ribosomes nickname is Protein Factories.
Ribosomes were observed in the 1950’s by George Palade. The term
"ribosome" was proposed in 1958 by Richard B. Roberts.
Cilia and Flagella
Cilia
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Hair like features used
to push cell or particles
located on the outside
of cell
Many hair like structures
beat to move the cell
Cilia means ‘eyelash’ in
Latin
Flagella
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A tail like projection
from the outside of a
cell used for movement
Tail whips back and
forth to push cell
forward i.e. Sperm
cells
Cilia and Flagella
http://www.dnatube.com/video/363/Cilia-and-Flagella
Website Information http://www.dnatube.com/video/363/Cilia-and-Flagella
Structures Unique to ….
Animal cells:
 Centrioles
Plant cells:
 Cell wall
 Plastids (chloroplast, amyloplast,
chromoplast)
 Crystals
The chloroplast is surrounded by a
double-layered composite
membrane with an intermembrane
space; further, it has reticulations, or many infoldings,
filling the inner spaces. The chloroplast has its own DNA,
which codes for redox proteins involved in electron
transport in photosynthesis; this is termed the plastome.
Chloroplast is one of the groups of organelles
in plant cells called plastids. This gives green
plants their color and transfers the energy in
sunlight into stored energy in carbohydrates
during photosynthesis.
Chloroplast was first suggested by Mereschkowsky in 1905
after an observation by Schimper in 1883 that chloroplasts
closely resemble cyanobacteria.
URL: http://en.m.wikipedia.org/wiki/Chromoplast?wasRedirected=true
URL: http://en.m.wikipedia.org/wiki/Chloroplast?wasRedirected=true
Amyloplasts are nonpigmented organelles found in
some plant cells.
They are responsible for the synthesis and storage
of starch granules, through the polymerization of
glucose. Amyloplasts also convert this starch back
into sugar when the plant needs energy.
Large numbers of amyloplasts can be found in fruit and in
underground storage tissues of some plants, such as in potato
tubers.
URL: http://en.m.wikipedia.org/wiki/Amyloplast?wasRedirected=true
Chromoplasts in the
traditional sense are
found in coloured organs
of plants such as fruit and
floral petals, to which
they give their distinctive
colors. This is always
associated with a massive
increase in the
accumulation of
carotenoid pigments. The
conversion of
chloroplasts to
chromoplasts in ripening
is a classic example.
Chromoplasts are
plastids responsible for
pigment synthesis and
storage. They, like all
other plastids (including
chloroplasts and
leucoplasts), are
organelles found in
specific photosynthetic
eukaryotic species.
The term "chromoplast" is occasionally utilized to include any plastid that has pigment, mostly to
emphasize the contrast with the various types of leucoplasts, which are those plastids that have no
pigments. In this sense, chloroplasts are a specific type of chromoplast. Still, "chromoplast" is more
often used to denote those plastids with pigments other than chlorophyll.
URL: http://en.m.wikipedia.org/wiki/Chromoplast?wasRedirected=true
Cell Wall
 Identifying Characteristics
 How the structure relates to
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of the Cell Wall
- Tough, flexible but sometimes
fairly rigid layer that surrounds
some types of cells.
 - Located outside the Cell
Membrane.
 - Provides structural support and
protection.
 - Acts as a filtering mechanism.
the function
The structure of the Cell Wall
relates to the function because the
structure of the Cell Wall is rigid
and tough to offer protection
against any stress that may be
present. The structure and the
function also relate because the
Cell Wall limits the entry of any
toxic molecules.
 The structure of the Cell Wall is the
function, it serves as a wall.
 Cell Wall’s Function
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Determining Cell Shape
- the shape of a plant is determined
by the cell wall, the cell wall is like a
skeleton acting as the main
supporting structure of a cell.
Strength
- provides strength to the cell, since
the cell wall is also flexible
Controlling Turgor Pressure
- an important function of a cell is to
maintain Turgor Pressure, Turgor
Pressure is the pressure applied by
the cell constituents on the cell wall.
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Passage of Substances
- the cell wall allows the movement
of small molecules like protein to go
in and out. But limits the large more
toxic molecules it will allow in.
Protection
- the cell wall is the first line of
defense against attacks.