EXPLORING_THE_CELL.PDF

EXPLORING

the Cell

W hat cells do, and

how cell biologists

study them

A publication of

T HE A MERICAN S OCIETY FOR

C ELL B IOLOGY

EXPLORING

the Cell

Photo Credits

Metaphase (cover): Conly Rieder, Cynthia Hughes.

CD95 in apoptosis (pg.1 and pg.16): Thomas Schwarz / Rockefeller University Press.

EM of cells on head of pin (pg.2): Tony Brain / Science Photo Library.

Blood vessels in skin (pg.2): Gabriele Bergers, Douglas Hanahan, Lisa Coussens / UBC Press.

DNA to RNA to protein (pg.3): ASCB.

Membrane compartments (pg.3): L. Andrew Staehelin.

Actin (pg.4): John Heuser.

Metabolism diagram (pg.4): Garland Publishing.

Dividing Drosophila embryo (pg.5): David Sharp, Jonathan Scholey / Rockefeller University Press.

Listeria movement (pg.6): Julie Theriot.

Immune cells escaping blood (pg.6): Martin Sandig / Company of Biologists.

Matrix degradation in pancreatic development (pg.7): Francisco Miralles / Rockefeller University Press.

Colon cancer cell invasion (pg.7): Kathy O’Connor, Arthur Mercurio / Rockefeller University Press.

Resorbing cell (pg.8): Teresa Burgess, Stephen Kaufman.

Osteoclast activity with and without OPGL (pg.8): Teresa Burgess, Stephen Kaufman / Rockefeller University Press.

Mitochondrial fusion (pg.8): Jodi Nunnari.

Glucose and iron entry (pg.9): Gary Herman / Rockefeller University Press.

Clathrin-coated pit (pg.9): John Heuser.

Dynamin spiral (pg.9): Kohji Takei, Pietro DeCamilli / Macmillan.

DNA replication (pg.10): Ronald Berezney / Rockefeller University Press.

Single kinesin motor (pg.10): Ron Vale / Rockefeller University Press.

Traffic light for cell (pg.11): R. Bruce Nicklas / Rockefeller University Press.

Cytokinesis and actin (pg.12): Yu-Li Wang / Rockefeller University Press.

Oscillator in frog eggs (pg.13): Marc Kirschner / National Academy of Sciences (USA).

Peroxisome formation (pg.13): Sarah South, Stephen Gould.

Gap junctions (pg.14): Paul Lampe / Rockefeller University Press.

Vesicle EM (pg.14): Peggy Weidman, John Heuser / Rockefeller University Press.

Golgi (pg.14): L. Andrew Staehelin / Rockefeller University Press.

Stripe formation in fly (pg.14): Henry Krause / Company of Biologists.

Photoreceptor cells and ommatidium (pg.15): Ernst Hafen / Cell Press.

Survivin (pg.16): Dario Altieri / Macmillan.

Worm cell death (pg.16): H. Robert Horvitz, Michael Hengartner / Macmillan.

Cell attachment (pg.17): Eduardo Almeida, Caroline Damsky.

Sympathetic neuron (pg.17): Paul Letourneau.

www.furman.edu/~snyder/careers/careers.html

Provides links to sites with information on career planning for anyone

interested in broad aspects of biologically oriented careers.

www.primex.co.uk/iob/d31.html

The Institute of Biology has produced a set of careers literature to help

school and college students discover the range of careers open in biology.

www.microscopy-uk.org.uk/mag/indexmag.html

Interactive magazine introducing students to instrumentation.

Acknowledgements

www.studyweb.com/

Commercial site has organized over 63,000 URLS of educational and

classroom importance.

This booklet was prepared with the generous support of

www.ed.gov/free

Internet teaching resources aimed primarily at the K-12 audience,

from 49 federal agencies. Animations, interviews and tutorials.

SmithKline Beecham

www.stanford.edu/group/Urchin/index.html

Over 150 web pages for high school biology teachers.

by the American Society for Cell Biology Education Committee:

www.sciencenet.org.uk/index.html

All areas of science are covered with a strong focus on biology and medicine.

Frank Solomon (Chair), Robert Bloodgood, Robert Blystone,

vector.cshl.org/dnaftb

Geared towards people without a scientific background.

Kay Broschat, Joan Brugge, Sarah Elgin, Elizabeth Gavis, Arthur Lander,

www.tulane.edu/~dmsander/garryfavweb.html

A general virology resource.

J. Richard McIntosh, Constance Oliver, Linda Silveira, Samuel Silverstein,

science-education.nih.gov/homepage.nsf

Web site for high school students and teachers.

www.nhgri.nih.gov/DIR/VIP

Site has a glossary of 150 genetic terms with illustrations and audio

tracks where various scientists at NIH describe the sense of the term.

Roger Sloboda and Christopher Watters.

Image research and text by William Wells.

pbs.org/wgbh/aso/tryit/dna/#

DNA workshop.

Layout and design by Designer’s Ink.

www.hoflink.com/~house/index.html

800 web resources for Biology teachers and students.

Managing Editor: Elizabeth Marincola.

www.cotf.edu

Bioblast - NASA funded multimedia project for teachers and students.

www4.nas.edu/beyond/beyounddiscovery.nsf

National Academy of Science case studies of recent technology and

medical advances.

For more information about the ASCB, contact the Society at

9650 Rockville Pike

www.classroom.net/home.asp

Adventure learning programs with interactive expeditions.

Bethesda, Maryland 20814

www.biologylessons.sdsu.edu

Biology lessons and teacher guides.

301-530-7153; 301-530-7139 (fax);

www.microbeworld.org

Facts, stories and vivid images. Links to microbe.org that helps stu-

dents explore the mysteries and wonders of microbes.

ascbinfo@ascb.org or www.ascb.org/ascb.

www.hhmi.org/GeneticTrail/

Blazing a genetic trail. Families and scientists joining in seeking the

flawed genes that cause disease.

schmidel.com/bionet.cfm

A guide to biology and chemistry educational resources on the web.

www.ncsu.edu/servit/bodzin/

A resource for primary, secondary, and university science educators.

Links to other science web sites.

Cloning figure (pg.18): FASEB.

Ultraviolet light triggers DNA damage in skin cells. This causes a protein,

CD95, to gather on the surface of the cells, forming the bright red

clusters seen here. The clusters send a signal to the cell to commit

suicide rather than risk becoming cancerous; see page 16.

EXPLORING

Cell biologists study life’s basic unit

the Cell

A parts list

What do cells do?

Cells move

What cells do, and

Cells eat

Cells reproduce

Cells communicate

Cells die

how cell biologists

Cloning

Animals and research

study them

Cover photograph:

A cell going through the cell division stage called mitosis. The

chromosomes, in blue, have duplicated and are lined up in the middle

of the cell by the spindle (yellow). The chromosomes contain DNA,

the information store of the cell. Tiny motor proteins in the cell use

the tracks of the spindle fibers to distribute one copy of each

chromosome to each of the two new cells. The red keratin filaments

form a protective cage around the spindle and the chromosomes.

EXPLORING

the Cell

What cells do, and

how cell biologists

study them

and oxygen and to remove wastes. Shown below at

top right is a magnified cross-section of normal skin;

the surface of the skin is at top. The top layer of cells

is thin and is fed by blood vessels below (in red). At

bottom right is a similar section from cancerous cells.

The top layer of cells has reproduced aggressively,

and has induced the growth of a large number of

blood vessels from below (in red, and in brown at

bottom left).

step is an undergraduate degree, commonly in one of

the sciences. Next, the student usually pursues a Ph.D.,

which typically takes about five or six years of courses

and laboratory work in several areas. In most Ph.D.

programs, the student is supported by grants that are

sufficient to live on and to pay tuition; in return the

student may help teach undergraduates. Once a sci-

entist has received the Ph.D., 3-6 years of indepen-

dent post-doctoral laboratory

work, under the supervision of a

professor, often follows.

Many cell biologists carry

out research in biotechnology or

drug companies. They use their

broad knowledge of how cells

work, and of technologies for

studying cells, to explore the cell’s

normal and abnormal function

and how to correct its defects.

Finding drugs is no longer a ques-

tion of hit-or-miss, but is highly dependent on un-

derstanding the biology of a disease as well as how

cells misbehave.

Cell biologists also bring valuable skills and

education to teaching (both high school and college),

the law (particularly patent law), policymaking (help-

ing government make informed laws and regula-

tions), business and finance (particularly in biotech-

nology) and writing (for newspapers, magazines,

popular books and textbooks).

A cancer needs food so it

attracts its own blood supply

Cell biologists study life’s basic unit

Cells are life’s basic building block. Cells are small—

above we see a few thousand bacterial cells on the

point of a pin. But a few trillion human cells together

becomes a person who can think, eat and talk. The

fate of the cells determines in large part the develop-

ment, health and lifespan of the person.

Many conditions and diseases start with one cell.

Sperm that can’t move properly can cause infertil-

ity. Arthritis or diabetes can be triggered by immune

cells that mistakenly attack the body’s own proteins.

And cancer results from cells growing when and

where they shouldn’t.

Cancerous cells ignore the normal limits on

growth. Once the cancer has grown to a certain stage,

it needs to attract blood vessels to supply it with food

What can a cell biologist do?

An education in cell biology is preparation for many different careers.

Cell biologists enjoy a range of careers , includ-

ing research in universities and biotechnology or

drug companies . Cell biologists are well trained in

critical and analytical thinking, skills that are desir-

able in many professions in addition to research,

including education and business.

To become an independent researcher, the first

Humans, plants and bacteria are all made from cells.

A parts list

Information is stored in DNA, read into RNA,

and converted into protein.

Each cell contains the information to create tens of thousands of proteins.

The cell is a self-sustaining machine, and the

information store that directs the machine’s op-

eration is DNA (top of diagram on left). DNA is

made up of building blocks called bases . Each hu-

man cell (except older red blood cells) has about

six billion bases of DNA. The DNA is organized

into genes, which vary in size from a few hundred

to over a million bases each. Groups of genes are

creates a lipid bilayer membrane , which surrounds

the cell and acts as its boundary. Lipid bilayers are

also used to define the nucleus (where the DNA is

kept, reproduced and read), the mitochondria (where

energy is produced), the endoplasmic reticulum and

Golgi (where proteins are sorted so they can be sent

to different locations), and the chloroplast (where

plants harvest light energy and make oxygen).

hooked together to make a chromosome .

Special proteins select genes to be copied into

RNA (middle of diagram on left). The RNA is then

converted by an established code into protein (bot-

tom of diagram on left). With a few exceptions,

each gene yields one protein.

Membranes create compartments.

The cell uses membranes to organize and segregate its activities.

Fat is an important component of a cell. The

shape of certain fat molecules makes them perfect for

making a barrier in the cell. The water-loving ends of

these fat molecules stick outward, and the water-

averse ends point inward, mixing only with each other.

A double layer of fat molecules in this arrangement

Above we see part of a green algae cell. The cell

has been frozen, opened and viewed with an electron

microscope. This reveals the membranes of the nucleus

(N, with nuclear pores for moving molecules in and

out), Golgi stacks (G) and chloroplast (C).

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