CELLS: - the Scientia Review
CELLS: - the Scientia Review
CELLS: - the Scientia Review
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<strong>CELLS</strong>:<br />
How <strong>the</strong>y started<br />
What <strong>the</strong>y are<br />
How to see <strong>the</strong>m<br />
Megan Riley<br />
Lauren McCarthy<br />
Nick Murray
Table of Contents<br />
What Is a Cell? 2<br />
Origins of Cells 3<br />
Robert Hooke 4<br />
Stanley Miller and Howard Urey 5<br />
Stromatolites 7<br />
Organelles 8<br />
Nucleus 9<br />
Ribosomes 10<br />
Chromosomes 11<br />
Cytoplasm 12<br />
Centioles 13<br />
Chloroplast 14<br />
Cytoskeleton 15<br />
Endoplasmic Reticulum 16<br />
Golgi Apparatus 18<br />
Mitochondrion 19<br />
Vacuole 20<br />
Lysosome 21<br />
Plasma Membrane 22<br />
Cell Wall 23<br />
Prokaryotic Cells 24<br />
Archaea 25<br />
Bacteria 26<br />
Eukaryotic Cells 27<br />
Protists 28<br />
Fungi 29<br />
Animal 30<br />
Plant 31<br />
Osmosis 32<br />
What Is a Microscope? 33<br />
History of Microscopes 34<br />
Origins 35<br />
The First Microscope 36<br />
Advances in Microscopes 37<br />
Hooke’s Microscope 38<br />
Optical Microscopes 39<br />
Electron Microscopes 40<br />
Interesting Images 42<br />
Glossary 44<br />
About <strong>the</strong> Authors 45<br />
Illustration Credits 46<br />
1
What is a Cell?<br />
All living organisms are made up of<br />
small units called cells. A cell is a<br />
collection of living matter enclosed<br />
by a membrane. Unicellular<br />
organisms are creatures that are<br />
made up of only one cell. The<br />
organisms known best, such as<br />
plants and animals, are<br />
multicellular, meaning <strong>the</strong>y are<br />
made up of more than one cell. An<br />
organism can have up to trillions of<br />
cells.<br />
Animals Cells<br />
Unicellular Organisms<br />
2
Origins of Cells<br />
Because cells are <strong>the</strong> basic unit of life, it<br />
is natural that we would wonder where<br />
<strong>the</strong>y came from; however, this question<br />
has remained unanswered. There are<br />
many <strong>the</strong>ories about how early<br />
molecules could produce life. A few<br />
hypo<strong>the</strong>ses involve deep-sea vents and<br />
lightening as <strong>the</strong> energy source that<br />
converted molecules into cells. The<br />
Miller-Urey experiment provided <strong>the</strong><br />
evidence to support <strong>the</strong> most<br />
commonly accepted hypo<strong>the</strong>sis (see<br />
pages 5-6).<br />
Did you know?<br />
Cells have been on earth for approximately 4 billion years.<br />
Modern humans have only been around for 200,000.<br />
3
Robert Hooke<br />
Robert Hooke was an English<br />
scientist who worked in a variety<br />
of scientific fields. He looked<br />
through a microscope at a piece<br />
of cork and named <strong>the</strong> small<br />
rectangles he saw cells.<br />
In addition to<br />
discovering cells,<br />
Robert Hooke made<br />
his own microscope.<br />
This image shows a piece of cork under a<br />
microscope. You can see <strong>the</strong> small dots or cells.<br />
In 1665, this news<br />
was extraordinary<br />
because cells were<br />
considered <strong>the</strong><br />
smallest parts of<br />
matter at that<br />
time.<br />
4
Stanley Miller and Howard Urey<br />
Stanley Lloyd Miller and<br />
Harold Urey, two American<br />
biochemists, worked<br />
toge<strong>the</strong>r on experiments in<br />
<strong>the</strong> 1950s. They engineered<br />
a device that used <strong>the</strong><br />
chemicals scientists predict<br />
were originally present on<br />
earth to produce organic<br />
compounds. At <strong>the</strong> time,<br />
<strong>the</strong>y thought only five<br />
organic compounds had<br />
been produced, but<br />
reanalysis shows that <strong>the</strong>re<br />
were actually twenty-two<br />
different molecules.<br />
5
Their experiments<br />
Miller and Urey added compounds into <strong>the</strong> largest<br />
container and <strong>the</strong>n started <strong>the</strong> experiment with an<br />
electric spark. You can fur<strong>the</strong>r see how <strong>the</strong><br />
apparatus worked. In <strong>the</strong> end it produced <strong>the</strong> first<br />
stages of cell development.<br />
6
Stromatolites<br />
s<br />
Stromatolites are layered<br />
structures formed of sediment and<br />
microorganisms, mostly<br />
cyanobacteria, which are known as<br />
green-blue algae or blue-green<br />
bacteria. Stromatolites are large<br />
fossils, and each layer in to <strong>the</strong><br />
center of <strong>the</strong> stromatolite allows<br />
scientists to look far<strong>the</strong>r into <strong>the</strong><br />
past as <strong>the</strong>y can look at ancient<br />
fossils of bacteria. These are some<br />
of <strong>the</strong> first records of life on earth.<br />
This is not your<br />
ordinary rock! The<br />
layers of this rock<br />
preserve <strong>the</strong><br />
earliest cells on<br />
earth.<br />
7
Organelles<br />
Located inside cells, organelles aid in<br />
biological processes. Some<br />
organelles, such as mitochondria and<br />
chloroplasts, are responsible for<br />
converting energy that <strong>the</strong> cell can<br />
use. O<strong>the</strong>r organelles, such as <strong>the</strong><br />
Golgi Apparatus, works in packaging<br />
proteins for transport. Eukaryotic<br />
cells have membrane enclosed<br />
organelles, while prokaryotic cells do<br />
not.<br />
8
Nucleus<br />
Every cell has a nucleus, a sphere located inside<br />
<strong>the</strong> cytoplasm. A nuclear membrane encloses <strong>the</strong><br />
nucleus but has openings for transport between <strong>the</strong><br />
nucleus and cytoplasm. Inside <strong>the</strong> nucleus is a<br />
nucleolus. This is a smaller sphere composed of<br />
RNA, which functions in producing ribosomes.<br />
Even though <strong>the</strong> nucleus is part of a larger unit<br />
(<strong>the</strong> cell), it has its own parts as well.<br />
9
Ribosomes<br />
Ribosomes are components of<br />
cells that make proteins. The DNA<br />
and RNA in a cell are known as<br />
<strong>the</strong> genetic code. The ribosomes<br />
follow this code and build<br />
proteins based on what <strong>the</strong> DNA<br />
tells <strong>the</strong>m to do. Ribosomes are<br />
made from RNA and protein.<br />
Ribosomes from different types<br />
of cells have different RNA<br />
sequences.<br />
10
Chromosomes<br />
Also located inside <strong>the</strong> nucleus are<br />
chromosomes, or strands of DNA that<br />
contain all <strong>the</strong> genetic coding for <strong>the</strong><br />
organism. Chromosomes come in<br />
pairs; every organism has a certain<br />
number of chromosome pairs. Each<br />
human has 46 chromosomes in 23<br />
pairs.<br />
These are <strong>the</strong> pairs of<br />
human chromosomes.<br />
Males have one X and<br />
one Y chromosome,<br />
whereas females have<br />
two Xs. Are <strong>the</strong><br />
chromosomes at <strong>the</strong><br />
right from a male or a<br />
female?<br />
11
Cytoplasm<br />
The cytoplasm is <strong>the</strong> part of <strong>the</strong> cell that is<br />
enclosed by <strong>the</strong> cell or plasma membrane.<br />
Every cell has cytoplasm. In prokaryotic cells,<br />
this is where all <strong>the</strong> functions of <strong>the</strong> cell take place.<br />
In eukaryotic cells, each important function has an<br />
organelle that focuses solely on that event. These<br />
organelles are located inside <strong>the</strong> cytoplasm.<br />
12
Centrioles<br />
Centrioles are long, thin,<br />
cylinders near <strong>the</strong> nucleus that are<br />
involved in cell division, or <strong>the</strong><br />
production of new cells. Each<br />
centriole has nine tubes, and each<br />
of <strong>the</strong>se nine tubes is composed of<br />
three tubules, or smaller tubes.<br />
Can you see <strong>the</strong> nine tubes each composed of three tubules?<br />
13
Chloroplasts<br />
The left image illustrates <strong>the</strong> structure of a single<br />
chloroplast; <strong>the</strong> photograph on <strong>the</strong> right displays <strong>the</strong><br />
chloroplasts within a plant cells.<br />
Chloroplasts are <strong>the</strong> organelles<br />
responsible for food production in plant cells.<br />
They contain chlorophyll, a green pigment<br />
that helps a plant convert sunlight into<br />
energy, stored in <strong>the</strong> form of sugar. This<br />
process is called photosyn<strong>the</strong>sis, and it occurs<br />
I <strong>the</strong> mesophyll cells inside of a leaf.<br />
14
Cytoskeleton<br />
Composed of microtubules, <strong>the</strong><br />
cytoskeleton helps <strong>the</strong> cell maintain<br />
its shape. They provide internal<br />
strength and structure and help keep<br />
all <strong>the</strong> organelles in <strong>the</strong> correct place.<br />
The cytoskeleton is also responsible<br />
for helping substances move around<br />
<strong>the</strong> cell.<br />
In this color<br />
enhanced<br />
photograph, <strong>the</strong><br />
cytoskeleton can<br />
be seen as <strong>the</strong><br />
green fiber-like<br />
structure. The blue<br />
dot is <strong>the</strong> nucleus<br />
and <strong>the</strong> red outline<br />
is <strong>the</strong> cell<br />
membrane of this<br />
cell.<br />
15
Smooth & Rough ER<br />
The rough endoplasmic reticulum has <strong>the</strong> same<br />
basic structure and functions as <strong>the</strong> smooth<br />
endoplasmic reticulum except that it has ribosomes<br />
scattered over its surface. These ribosomes are<br />
responsible for manufacturing protein for <strong>the</strong> cell.<br />
The smooth endoplasmic reticulum is a<br />
tubular network in <strong>the</strong> cytoplasm. It is attached<br />
both to both <strong>the</strong> nuclear and cell membrane and<br />
aids in <strong>the</strong> movement of materials throughout <strong>the</strong><br />
cell. Various cell materials are separated and<br />
stored here.<br />
16
Endoplasmic Reticulum<br />
Here you can see <strong>the</strong> two types of endoplasmic<br />
reticulum; <strong>the</strong> smooth endoplasmic reticulum has no<br />
ribosomes.<br />
17
Golgi Apparatus<br />
Located near <strong>the</strong> nucleus, <strong>the</strong> Golgi<br />
apparatus is <strong>the</strong> structure in which<br />
proteins and lipids that have been<br />
manufactured are packaged. This<br />
means <strong>the</strong>y are prepared to be taken<br />
out of <strong>the</strong> cell and transported<br />
elsewhere in <strong>the</strong> organism. This<br />
structure is made up of layers of<br />
membranes that form sacs.<br />
The Golgi Apparatus processes and packages proteins and<br />
lipids.<br />
18
Mitochondrion<br />
The<br />
mitochondrion<br />
is sometimes<br />
called <strong>the</strong><br />
power house of<br />
<strong>the</strong> cell.<br />
The mitochondrion is <strong>the</strong> second largest organelle<br />
in <strong>the</strong> cell. This organelle has a unique genetic<br />
structure, and <strong>the</strong>re is a <strong>the</strong>ory that mitochondria<br />
used to be independent, free-living cells that<br />
became imbedded in o<strong>the</strong>r cells as organelles. This<br />
part of <strong>the</strong> cell is responsible for producing ATP<br />
(adenosine triphosphate) which cells use as energy.<br />
19
Vacuole<br />
A vacuole is part of plant and fungal<br />
cells, as well as some protist and<br />
animal cells. Vacuoles are sacs filled<br />
with water, waste, and o<strong>the</strong>r cellular<br />
substances.<br />
This is a<br />
vacuole in a<br />
plant cell.<br />
20
Lysosome<br />
The lysosome is a vesicle, or sac, that<br />
transports <strong>the</strong> cells waste to <strong>the</strong> cell<br />
membrane where it is carried out of<br />
<strong>the</strong> cell. If a lysosome opens, <strong>the</strong> cell<br />
breaks down because <strong>the</strong> digestive<br />
enzymes in <strong>the</strong> lysosome destroys all<br />
of <strong>the</strong> cell parts.<br />
A lysosome can destroy a cell.<br />
21
Plasma Membrane<br />
This is <strong>the</strong> outside of <strong>the</strong> cell, also known as <strong>the</strong> cell<br />
membrane which encloses all <strong>the</strong> cell’s organelles.<br />
This double layer of lipid molecules has embedded<br />
proteins.<br />
The plasma membrane is <strong>the</strong> flexible<br />
layer that surrounds <strong>the</strong> cell. This<br />
part of <strong>the</strong> cell allows certain<br />
molecules to pass in and out of <strong>the</strong><br />
cell interior, while o<strong>the</strong>r molecules<br />
are blocked. Proteins are placed<br />
throughout <strong>the</strong> cell membrane and<br />
allow materials that are too large to<br />
pass through <strong>the</strong> membrane itself.<br />
22
Cell Wall<br />
A cell wall is a rigid structure made<br />
of cellulose fibers surrounding a cell<br />
membrane. There are two layers—<br />
<strong>the</strong> first is flexible and forms around<br />
<strong>the</strong> membrane, while <strong>the</strong> outer<br />
layer is much stronger and doesn’t<br />
form until after <strong>the</strong> cell has grown<br />
to its full size. These cell walls are<br />
usually found in plant cells.<br />
The light green<br />
structure shown to<br />
<strong>the</strong> left is a cell wall<br />
which protects <strong>the</strong><br />
cell more than a cell<br />
membrane; it also<br />
constricts <strong>the</strong> cell<br />
because it prevents<br />
flexibility.<br />
23
Prokaryotic Cells<br />
Prokaryotic cells function without a<br />
nuclear membrane or organelles.<br />
All biological processes happen<br />
directly in <strong>the</strong> cytoplasm instead of<br />
individual organelles. These small<br />
cells are only about <strong>the</strong> size of<br />
animal cell mitochondria.<br />
Prokaryotic cells are not part of<br />
multicellular organisms.<br />
As you can see, prokaryotic cells lack a nucleus. The<br />
DNA is located directly in <strong>the</strong> cytoplasm.<br />
24
Archaea<br />
Originally confused with true bacteria,<br />
cells of Archaea are rod-shaped or<br />
spherical in shape. They were<br />
originally considered a part of <strong>the</strong><br />
bacteria kingdom, but biochemical<br />
research shows that <strong>the</strong> two cell<br />
groups are not related. These cells live<br />
in some of <strong>the</strong> most extreme<br />
environments on earth. They are most<br />
closely related to <strong>the</strong> earliest cells on<br />
earth.<br />
25
Bacteria<br />
Bacterial cells have three basic<br />
shapes: rods, spheres, and<br />
spirals. They can live in nearly<br />
every environment on Earth.<br />
They interact with organisms<br />
in all <strong>the</strong> o<strong>the</strong>r kingdoms.<br />
Did you know?<br />
There are<br />
approximately 40<br />
million bacteria<br />
cells in one gram of<br />
soil and 1 million<br />
bacteria in 1/1000<br />
liter of fresh water!<br />
The number of<br />
bacteria in <strong>the</strong><br />
human body<br />
outnumbers human<br />
cells 10 to 1.<br />
This is a picture of E. coli bacteria taken under a<br />
scanning electron microscope. E. coli bacteria can<br />
cause food poisoning in humans.<br />
26
Eukaryotic Cells<br />
Eukaryotic cells are different from<br />
prokaryotic cells because <strong>the</strong><br />
nucleus is surrounded by a nuclear<br />
membrane. There is sometimes a<br />
combination of membrane-bound<br />
organelles inside eukaryotic cells as<br />
well. All kingdoms of multicellular<br />
organisms are composed of<br />
eukaryotic cells.<br />
This is a typical eukaryotic cell, but look for<br />
differences among <strong>the</strong> various types of eukaryotic<br />
cells.<br />
27
Protists<br />
There are a wide variety of<br />
protists, and <strong>the</strong>y are <strong>the</strong> only<br />
eukaryotic cells that are unicellular<br />
for a major part of <strong>the</strong>ir life cycles.<br />
They can survive in a variety of<br />
aquatic environments ranging<br />
from ponds and streams to mud<br />
and even <strong>the</strong> hair of polar bears.<br />
Protists are eukaryotic and unicellular for<br />
most of <strong>the</strong>ir life cycles.<br />
28
Fungi<br />
Fungal cells, or fungi, have a cell<br />
wall like plant cells, but <strong>the</strong> wall is<br />
made up of chitin instead of<br />
cellulose (see page 23). These<br />
cells obtain <strong>the</strong>ir energy by<br />
decomposing o<strong>the</strong>r dead<br />
organisms. Even though fungal<br />
cells have cell walls like plants,<br />
<strong>the</strong>y have been discovered to be<br />
more closely related to animal<br />
cells.<br />
These fungi are<br />
commonly known<br />
as mushrooms.<br />
They can be seen<br />
feasting on <strong>the</strong><br />
dead bark present.<br />
29
Animal<br />
Animal cells are eukaryotic and contain all <strong>the</strong><br />
organelles except for a cell wall and chloroplasts.<br />
The cell wall was lost through evolution as animal<br />
cells needed <strong>the</strong> capability to be more flexible than<br />
plant cells. Animals obtain energy by eating and<br />
digesting food not by converting sunlight into sugar,<br />
so <strong>the</strong>y do not have a need for chloroplasts.<br />
Here is a illustration of an animal cell with all its typical organelles.<br />
30
Plant<br />
Plant cells are also eukaryotic and have organelles<br />
including chloroplasts and cell walls. They have a<br />
large vacuole which acts as one large storage tank<br />
for <strong>the</strong> waste products of <strong>the</strong> cell.<br />
Look at this plant cell compared to <strong>the</strong> animal cell on<br />
<strong>the</strong> previous page. Do you notice different organelles?<br />
31
Osmosis<br />
Osmosis is <strong>the</strong> movement of water particles<br />
through <strong>the</strong> plasma membrane. This membrane is<br />
partially permeable which means that some particles<br />
can move through it while some cannot. This process<br />
allows <strong>the</strong> cell to maintain <strong>the</strong> correct amount of<br />
nutrients in <strong>the</strong> cell.<br />
Did you know?<br />
The average animal cell is composed of 95% water and 5% diluted salts. Cells<br />
in isotonic solutions (<strong>the</strong> same percentages) maintain <strong>the</strong>ir shape. Cells in<br />
hypertonic solutions are in solutions with more salt solutes than water. This<br />
means that water leaves <strong>the</strong> cell. Cells in hypotonic solutions show <strong>the</strong><br />
opposite effect.<br />
32
What Is a Microscope?<br />
A microscope is a tool used to<br />
cause small objects to appear<br />
larger. It is used to see close-up<br />
views of small objects so <strong>the</strong>y<br />
can be examined easily. The main<br />
types of microscopes are optical<br />
microscopes and electron<br />
microscopes. The pictures from<br />
microscopes can appear as <strong>the</strong>y<br />
are currently occurring like a<br />
movie or <strong>the</strong>y can be static<br />
pictures and unmoving.<br />
Microscopes are helpful to<br />
doctors and scientists to examine<br />
different organisms or molecules.<br />
Most common<br />
type of<br />
microscope: <strong>the</strong><br />
optical<br />
microscope<br />
33
History<br />
The first microscopes were simple<br />
glass lenses. No one knows when<br />
<strong>the</strong>se lenses were invented. The<br />
first records of such lenses are<br />
those of <strong>the</strong> ancient Romans,<br />
Seneca and Pliny <strong>the</strong> Elder. This<br />
was during <strong>the</strong> first century, and<br />
<strong>the</strong> Romans didn’t have many uses<br />
for <strong>the</strong> lenses. They used <strong>the</strong><br />
lenses to burn objects and to<br />
magnify smaller objects. This was<br />
somewhat like a magnifying glass.<br />
A common<br />
magnifying glass<br />
34
The Origin of <strong>the</strong> Microscope<br />
During <strong>the</strong> 13 th century, that’s <strong>the</strong><br />
1200s, lenses were used to create<br />
spectacles. This aided in <strong>the</strong> sight of<br />
people who had problems with sight.<br />
The lenses in <strong>the</strong> spectacles were first<br />
named lenses at this time.<br />
Soon, <strong>the</strong>se advances were used to<br />
create a simple microscope. It was a<br />
short tube with one lens on each side.<br />
These early microscopes were able to<br />
magnify objects to a size time times of<br />
what <strong>the</strong>y would normally look like.<br />
The first lenses were enclosed in <strong>the</strong><br />
tube-like structure above.<br />
35
The First Microscope<br />
The first real microscope was built by<br />
two Dutchmen, Zaccharias and Hans<br />
Janssen. They were putting multiple<br />
lenses into a tube and found that<br />
looking through it made objects far<br />
larger than earlier microscopes. This<br />
concept was expanded into <strong>the</strong><br />
compound microscope and <strong>the</strong><br />
telescope. Galileo, <strong>the</strong> fa<strong>the</strong>r of<br />
astronomy and physics, also<br />
experimented with <strong>the</strong>se devices and<br />
greatly improved <strong>the</strong>m. He added a<br />
focusing device and increased <strong>the</strong><br />
magnification.<br />
Galileo, <strong>the</strong> fa<strong>the</strong>r of<br />
astronomy and physics<br />
36
Advances in Microscopes<br />
The next advances in microscopes<br />
were contributed by Antonie van<br />
Leeuwenhoek. He spent most of<br />
his life studying lenses and<br />
invented new ways to perfect a<br />
lens. He made a lens by hand that<br />
magnified images by 270 times.<br />
He was <strong>the</strong> first person to use a<br />
microscope to view microscopic<br />
life. He viewed bacteria, yeast,<br />
and countless o<strong>the</strong>r creatures<br />
with his microscope.<br />
Leeuwenhoek’s<br />
microscope<br />
37
Hooke’s Microscope<br />
Over <strong>the</strong> next few years, different<br />
improvements were made to <strong>the</strong><br />
microscope. Robert Hooke (see<br />
page 4) built a copy of<br />
Leeuwenhoek’s microscope and<br />
made a few improvements to <strong>the</strong><br />
magnification.<br />
Robert Hooke’s<br />
microscope<br />
Currently, microscopes have<br />
magnification of up to 1250 times<br />
in ordinary light. This is as small as<br />
magnification can get on an<br />
ordinary microscope. A special<br />
type can view smaller objects but<br />
we’ll talk about that later.<br />
38
Optical Microscopes<br />
All of <strong>the</strong>se early microscopes are classified as<br />
optical microscopes. Sometimes called light<br />
microscopes, <strong>the</strong>y use <strong>the</strong> properties of light and<br />
groups of lens to enlarge images. They are very<br />
useful for viewing small objects but <strong>the</strong>y can’t view<br />
an object that is less than <strong>the</strong> wavelength of light.<br />
Visibilty also suffers with extremely small sizes.<br />
Did you know?<br />
Wavelengths of different colors<br />
The wavelength of<br />
light that humans<br />
can see is between<br />
390 to 750<br />
nanometers. This is<br />
a size so small that<br />
it would take 25400<br />
lengths of 750<br />
nanometers to<br />
reach across a<br />
penny.<br />
39
Electron Microscopes<br />
Ano<strong>the</strong>r type of microscope is <strong>the</strong><br />
electron microscope. It can be used<br />
to view objects that are smaller<br />
than <strong>the</strong> wavelength of light. This is<br />
done by using a beam of electrons<br />
in place of light. The electrons are<br />
<strong>the</strong>n used to form a magnified<br />
image of <strong>the</strong> object. This method is<br />
far more effective than one using<br />
light. The magnification from an<br />
electron microscope is able to reach<br />
levels up to 1,000,000 times <strong>the</strong><br />
normal magnification. The worst<br />
problem with electron microscopes<br />
is that <strong>the</strong>y are very expensive and<br />
cannot be used to magnify living<br />
cells.<br />
40
The electron microscope was first<br />
designed and built by Ernst Ruska,<br />
a physicist, and Max Knoll, an<br />
engineer, in 1931. This first<br />
version could only magnify up to<br />
400 times. Two years after that,<br />
scientists built a more advanced<br />
version that could magnify more<br />
than <strong>the</strong> best optical microscope<br />
in <strong>the</strong> world. This basic design has<br />
remained in use with few changes<br />
made to it. There are both<br />
scanning and transmission<br />
electron microscopes, which<br />
differ in whe<strong>the</strong>r <strong>the</strong> beam of<br />
electron is used to scan <strong>the</strong><br />
outside surface or see interior<br />
structure of a cell.<br />
A modern electron microscope<br />
41
Interesting Images<br />
Using <strong>the</strong> electron microscope<br />
A virus viewed using a<br />
scanning electron<br />
microscope<br />
An ant viewed using a<br />
scanning electron microscope<br />
42
A tardigrade, a<br />
microscopic waterdwelling<br />
animal, is<br />
often called a<br />
water-bear because<br />
of <strong>the</strong> way it<br />
moves. It is an<br />
unusual creature<br />
that can survive <strong>the</strong><br />
most extreme<br />
climates.<br />
Photograph taken<br />
using a scanning<br />
electron<br />
microscope<br />
A spider<br />
photographed<br />
using a scanning<br />
electron<br />
microscope<br />
43
Glossary<br />
Cell division: when one cell splits into two cells<br />
Cell wall: rigid structure surrounding <strong>the</strong> cell membrane<br />
Cell: a collection of living matter enclosed by a membrane<br />
Centrioles: long and thin cylinders near <strong>the</strong> nucleus responsible for cell division<br />
Chloroplasts: an organelle responsible for turning sunlight into energy for a plant cell<br />
Chromosomes: strands of condensed DNA<br />
Cytoplasm: inner “filling” of <strong>the</strong> cell where all <strong>the</strong> biological processes take place in prokaryotic cells<br />
cytoskeleton: <strong>the</strong> part of <strong>the</strong> cell that helps its maintain its shape<br />
Endoplasmic Reticulum: tubuluar network in <strong>the</strong> cytoplasm attached to both <strong>the</strong> nucleus and <strong>the</strong><br />
plasma membrane<br />
Eukaryotic cells: uni or multi cellular cells with or without organelles<br />
Golgi Apparatus: an organelle where proteins and lipids are packaged<br />
Green chlorophyll: <strong>the</strong> substance in chloroplasts that is responsible for photosyn<strong>the</strong>sis<br />
Lipds: fats<br />
Microscope: a tool used to make small objects appear larger<br />
microtubules: hollow cylinders that make up <strong>the</strong> cytoskeleton<br />
Mitochondrion: organelle responsible for <strong>the</strong> production of energy<br />
Multicellular: having more than one cell<br />
Nuclear Membrane: a membrane enclosing <strong>the</strong> nucleus that allows materials to pass in adn out of<br />
<strong>the</strong> nucleus<br />
Nucleolus: a small sphere inside <strong>the</strong> nucleus where RNA are stored<br />
Nucleus: a sphere located into <strong>the</strong> cytoplasm that acts as <strong>the</strong> control center for <strong>the</strong> cell<br />
Organelles: parts of a cell responsible for aiding <strong>the</strong> cell in biological processes<br />
Organic compounds:<br />
Osmosis: <strong>the</strong> movement of water particles across a membrane<br />
Photosyn<strong>the</strong>sis: <strong>the</strong> process in which sunlight is turned into energy<br />
Plasma Membrane: flexible material that surrounds a cell<br />
Prokaryotic cells: unicellular cells without organelles<br />
Ribosomes: components of <strong>the</strong> cell that make proteins<br />
RNA: <strong>the</strong> part of a cell that manufactures proteins<br />
Stromatolites: layered structured formed of sediment and microorganisms<br />
Tubules: small tubes<br />
Vacuole: an organelle is a sac filled with liquids<br />
Vesicle: a sac<br />
44
About <strong>the</strong> Authors<br />
Megan Riley, Nick Murray, and Lauren McCarthy<br />
are all junior students who attend <strong>the</strong><br />
Massachusetts Academy of Ma<strong>the</strong>matics and<br />
Science. Megan Riley has won a first place award<br />
in <strong>the</strong> Massachusetts State Science Fair; in her<br />
spare time she cheerleads and volunteers at her<br />
church. Nick enjoys hiking and swimming. His<br />
favorite subject is math. In his free time he mods<br />
video games and tries to write. Lauren rides<br />
horseback; her favorite subject is biology, and<br />
she wants to become an equine veterinarian.<br />
Nick Murray Lauren McCarthy Megan Riley<br />
45
46<br />
Illustration Credits<br />
<br />
http://micro.magnet.fsu.edu/cells/centrioles/images/centriolesfigure1.jpg<br />
<br />
http://library.thinkquest.org/C004535/media/golgi_apparatus.gif<br />
<br />
http://upload.wikimedia.org/wikipedia/commons/0/09/FluorescentCells.jpg<br />
<br />
http://www.abcbodybuilding.com/magazine03/mitochondria.jpg<br />
<br />
http://www.greetin.gs/phoebecell/photogallery/vacuole.jpg<br />
<br />
http://www.astbury.leeds.ac.uk/facil/ElectronMicro/F20microscope.jjp<br />
<br />
http://www.geology.sdsu.edu/seminars/fall08/stromatolite.jpg<br />
<br />
http://www.stolaf.edu/people/giannini/cell/lys/lysosomesfigure1.jpg<br />
<br />
http://www.cartage.org.lb/en/<strong>the</strong>mes/Sciences/Zoology/AnimalPhysiology/A<br />
natomy/AnimalCellStructure/Nucleus/cellnucleus.jpg<br />
<br />
http://www.ikkeweer.net/cats-o<strong>the</strong>rfiles/chromo.gif<br />
<br />
http://brainiedeal.files.wordpress.com/2009/06/whattttttttttttttt.jpg<br />
<br />
http://www.redesepalcala.org/olivaryescuela/divulgacion/3_Feria_Sevilla/Pro<br />
yecto/RobertHooke.jpg<br />
<br />
http://universe-review.ca/I11-40-SMiller.jpg<br />
<br />
http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment<br />
<br />
http://www.bio.miami.edu/~cmallery/150/phts/c8.1x4.chloroplasts.jpg<br />
<br />
http://en.wikivisual.com/images/1/11/Chloroplast-new.jpg<br />
<br />
http://sciencecity.oupchina.com.hk/biology/student/glossary/img/cytoplasm.j<br />
pg<br />
<br />
http://www.ucl.ac.uk/~sjjgsca/cellEndoMembranes.gif<br />
<br />
http://www.ccs.k12.in.us/chsBS/kons/kons/eukaryotic%20cell/cytoplasm_and<br />
_its_associated_str_files/image002.jpg<br />
<br />
http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment<br />
<br />
http://en.wikipedia.org/wiki/Robert_Hooke<br />
<br />
http://en.wikipedia.org/wiki/Stromatolite<br />
<br />
http://library.thinkquest.org/C004535/media/cell_membrane.gif<br />
<br />
http://biology.unm.edu/ccouncil/Biology_124/Images/cellwall.jpeg<br />
<br />
http://images.encyclopedia.com/getimage.aspx?id=2792724<br />
<br />
http://en.wikipedia.org/wiki/Escherichia_coli<br />
<br />
http://www.molecularexpressions.com/cells/animals/images/animalcell.jpg<br />
<br />
http://scienceblogs.com/clock/upload/2006/11/a2%20animal%20cell.png<br />
<br />
http://kdhellner.tripod.com/sitebuildercontent/sitebuilderpictures/.pond/pro<br />
tist.jpg.w300h223.jpg<br />
<br />
http://en.wikipedia.org/wiki/File:Osmotic_pressure_on_blood_cells_diagram.<br />
svg