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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

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