Cell Biology

Science Explorer – Cells and Heredity

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 Cell Lesson Index
 1.1 - Discovering Cells
 1.2 - Looking Inside Cells
 1.3 - Chemical Compounds in Cells
 1.4 - The Cell in its Environment
 2.1 - Photosynthesis
 2.2 - Respiration
 2.3 - Cell Division
 2.4 - Cancer
Science Explorer
Cells and Heredity

1.1 - DISCOVERING CELLS

1.1 - Discovering Cells - Related Videos

 The Discovery of Cells

 Cell Theory
 Parts of a Compound Microscope
 How to use a Microscope
 Greg Mendel – Meiosis Song
 Objectives
1. How did the invention of the
microscope contribute to scientists’
understanding of living things?
2. What is the cell theory?
3. How does a lens magnify an object?
Cells
 Cells are the basic
units of structure
and function in
living things.
 Most cells are too
small to be seen
with the naked eye.
Microscope
 The invention of
the microscope
made it possible for
people to discover
and learn about
cells.
Microscopes
 A microscope is
an instrument that
makes small
objects look larger.
 Some microscopes
do this by using
lenses to focus
light.
 Simple Microscope

 A simple light
microscope contains
only one lens.
Compound Microscope
 A light microscope
that has more than
one lens is called a
compound
microscope.
 Cells

 One of the first

people to observe
cells was Robert
Hooke.
Cells
 In 1663, Hooke
observed the
structure of a thin
slice of cork using
a compound
microscope he had
built himself.
Cells
 At about the same
time, Anton van
Leeuwenhoek
began to construct
microscopes and
use them to
observe tiny
objects.
Cells
 Leeuwenhoek was
the first person to
see the single-
celled organisms
that are now called
bacteria.
Plant Cells
 In 1838 Matthais
Schleiden
concluded that all
plants are made up
of cells.
Animal Cells

 The next year,

Theodor Schwann
concluded that all
animals are also
made up of cells.
Cell Theory
 In 1855 Rudolf
Virchow proposed
that new cells are
formed only from
existing cells.
Cell Theory
 The observations
and conclusions of
Hooke,
Leeuwenhoek,
Schleiden,
Schwann, Virchow,
and others led to
the development of
the cell theory.
Cell Theory
 The cell theory
states;
◦ all living things are
composed of cells
◦ cells are the basic
unit of structure and
function in living
things
◦ all cells are
produced from other
cells.
Microscope Properties
 For a microscope
to be useful, it must
combine two
important
properties—
magnification and
resolution.
 Microscope Magnification
 Magnification is the
ability to make things
look larger than they
are.
 The lens or lenses in
a light microscope
magnify an object by
bending the light that
passes through them.
 Microscope Magnification

 A lens that
magnifies is
thicker in the
center than at
the edges and
is called a
convex lens.
Compound Microscope
Magnification
 Because a
compound
microscope uses
more than one
lens, it can magnify
an object more
than a simple
microscope.
Compound Microscope
Magnification
 The total
magnification of
a compound
microscope is
equal to the
magnifications
of the two
lenses
multiplied
together.
 Resolution
 The ability to clearly
distinguish the
individual parts of an
object is called
resolution.
 Resolution is another
term for the
sharpness of an
image.
Electron Microscopes
 Since the 1930s,
scientists have
developed different
types of electron
microscopes,
which use a beam
of electrons instead
of light to examine
a specimen.
Electron Microscopes
 Because they use
tiny electrons to
produce images,
the resolution of
electron
microscopes is
much better than
the resolution of
light microscopes.
END – 1.1
Science Explorer
Cells and Heredity

1.2 - LOOKING INSIDE CELLS

1.2 - Looking Inside Cells - Related
Videos
 Cell Membrane – Cell Wall  Nucleus
 Cell Organelles  Passive and Active Transport
 Cell Wall  Powering the Cell Mitochondria
 Cell Wall and Plasma Membrane  Ribosomes
 Chloroplasts  The Cytoplasm Blues
 Chromatin  The Nucleus
 Cytoskeleton – Cytoplasm  The Plasma Membrane
 Endoplasmic Reticulum  Transport Across the Cell
 Eukaryotic Cells Membrane
 Golgi Apparatus  Vacuoles – Vesicles
 Journey Inside the Cell  Voyage inside the Cell Membrane
 Lysosomes  What are Vacuoles?
 Mitochondria ATP Synthesis
Objectives
1. What role do the cell membrane and
nucleus play in the cell?
2. What functions do other organelles in
the cell perform?
3. How do bacterial cells differ from
plant and animal cells?
Organelles
 Inside a cell are
tiny structures
called organelles,
which carry out
specific functions in
the cell.
 Organelles include
the cell wall, cell
membrane, and
nucleus.
Cell Wall
 The cell wall is a
rigid layer of
nonliving material
that surrounds
plant cells. It helps
protect and support
a cell. Although the
cell wall is stiff,
many materials can
pass through it.
Cell Membrane
 In cells that
do not have
cell walls, the
cell
membrane is
the outside
boundary that
separates the
cell from its
environment.
 Cell Membrane
 There are tiny
openings, or pores,
in the cell membrane
through which
materials can enter
or leave the cell.
Cell Membrane
 One of the cell
membrane’s
main functions
is to control
what
substances
come into and
out of a cell.
 Nucleus
 The nucleus
is a large,
oval
structure that
acts as the
“brain” of the
cell.
Nucleus
 You can think of
the nucleus as the
cell’s control
center, directing all
of the cell’s
activities.
Nuclear Membrane
 The nucleus is
surrounded by a
nuclear membrane.
Nuclear Membrane
 Materials pass in
and out of the
nucleus through
small openings, or
pores, in the
nuclear membrane.
Chromatin
 Floating in the nucleus are thin strands called
chromatin, which contains the genetic
material, or the instructions for cell functions.
Nucleolus
 The nucleus
also contains
the nucleolus,
a structure
where
ribosomes
are made.
Cytoplasm
 The cytoplasm is
the region between
the cell membrane
and the nucleus.
Many cell
organelles are
found in the
cytoplasm.
 Organelles
 The
organelles
function to
produce
energy, build
and transport
needed
materials,
and store and
recycle
wastes.
 Mitochondria

 Rod-shaped organelles called mitochondria

produce energy.
Endoplasmic Reticulum
 A maze of
passageways
called the
endoplasmic
reticulum
carries proteins
and other
materials from
one part of the
cell to another.
 Ribosomes
 Small,
grainlike
bodies
called
ribosomes
produce
proteins.
 Golgi Bodies
 Collections of
sacs and tubes
called Golgi
bodies
distribute
proteins and
other materials
throughout the
cell.
 Chloroplasts
 In plants and some other organisms, large,
green structures called chloroplasts capture
energy from sunlight and use it to produce food
for the cell.
 Vacuole

 A large sac called a vacuole stores food and

other materials in the cell.
 Lysosomes
 Small, round
structures
called
lysosomes
break down
food and
recycle old
cell parts.
 Bacterial Cell
 A bacterial cell is
smaller than a
plant or animal cell.
 While a bacterial
cell does have a
cell wall and a cell
membrane, it does
not contain a
nucleus.
Bacterial Cell
 A bacterial cell
also contains
ribosomes but
none of the
other organelles
found in plant or
animal cells.
 Many-celled Organisms
 In many-celled
organisms, the
cells are often quite
different from each
other. The structure
of each kind of cell
is suited to the
function it carries
out in the
organism.
END – 1.2
Science Explorer
Cells and Heredity

1.3 - CHEMICAL COMPOUNDS IN CELLS

1.3 - Chemical Compounds in Cells – Related
Videos
 Atoms and The Periodic Table
 Biology Amino Acids and the R Group
 Biology Proteins Amino Acids
 Enzymes
 From DNA to Protein
 Lipid
 Lipids
 Nova Science Now Amazing Atoms
 Nucleic Acids
 Organic Compounds
 Organic Molecules Carbohydrates
 Protein Structure
 They Might be Giants – Meet the Elements
 What is a Chemical Compound?
Objectives
1. What are the four main kinds of
organic molecules in living things?
2. How is water important to the
function of cells?
 Element

 An element is any substance that cannot be

broken down into simpler substances.
 Atom
 The smallest unit of an element is called an
atom.
 CHON

 The most common elements in living things

are carbon, oxygen, hydrogen, and nitrogen
 Compound
 When two or
more elements
combine
chemically,
they form a
compound.
Molecule
 The smallest unit of most compounds is
called a molecule.
 Compounds in Living Things
 Many of the
compounds found
in living things
contain the
element carbon,
which is usually
combined with
other elements.
Organic Compounds

 Most compounds that

contain carbon are
called organic
compounds.
 Organic Compounds
 The most
important groups
of organic
compounds found
in living things are
carbohydrates,
lipids, proteins,
and nucleic acids.
Inorganic Compounds
 Compounds
that do not
contain the
element
carbon are
called
inorganic
compounds.
 Carbohydrates
 A carbohydrate is
an energy-rich
organic compound
made of the
elements carbon,
hydrogen, and
oxygen.
 Carbohydrates
 Sugars and starches are examples of
carbohydrates.
 Carbohydrates
 Carbohydrates
are important
components of
some cell
parts,
including cell
walls and cell
membranes.
 Carbohydrates
 Carbohydrates also provide cells with energy.
 Proteins
 Proteins are
large organic
molecules made
of carbon,
hydrogen,
oxygen,
nitrogen, and, in
some cases,
sulfur.
Proteins
 Cells use
proteins for cell
membranes and
many of the
organelles
within the cell.
 Amino Acids
 Protein
molecules are
made up of
smaller
molecules called
amino acids.
Enzyme
 An enzyme
is a type of
protein that
speeds up
a chemical
reaction in
a living
thing.
 Enzymes
 Without
enzymes,
many
chemical
reactions that
are necessary
for life would
either take too
long or not
occur at all.
 Lipids
 Fats, oils, and waxes
are all lipids.
 Lipids are energy-
rich organic
compounds made of
carbon, hydrogen,
and oxygen.
 The Lipid called Cholesterol
 One type of
lipid,
called
cholesterol, is
an important
component of
animal cell
membranes.
Cholesterol
 Your liver normally
produces enough
cholesterol to meet
your body’s needs.
 However, many of the
foods you eat also
contain cholesterol.
 Cholesterol
 If your diet
contains too much
cholesterol,
excess amounts
of cholesterol can
collect along the
walls of blood
vessels and block
the flow of blood.
 Nucleic Acids
 Nucleic acids
are very large
organic
molecules made
of carbon,
oxygen,
hydrogen,
nitrogen, and
phosphorus.
 Nucleic Acids
 Nucleic acids
contain the
instructions that
cells need to
carry out all the
functions of life.
 Nucleic Acids
 There are two
kinds of
nucleic acids:
DNA and
RNA.
 DNA
 Deoxyribonucleic
acid, or DNA, is
passed from parent
to offspring and
directs all of the cell’s
functions.
 RNA
 Ribonucleic acid, or
RNA, plays an
important role in the
production of
proteins.
 H2O
 Water plays
many vital roles
in cells. Without
water, most
chemical
reactions within
cells could not
take place.
 H2O
 Water also helps
cells keep their
size and shape
and helps keep
the temperature
of cells from
changing rapidly.
END – 1.3
Science Explorer
Cells and Heredity

1.4 - THE CELL IN ITS ENVIRONMENT

1.4 - The Cell in its Environment – Related
Videos

 Active Transport
 Diffusion & Osmosis
 Passive & Active Transport
 Passive Transport
 Objectives
1. By what three methods do materials
move into and out of cells?
2. What is the difference between
passive transport and active transport?
Cell Membrane
 The cell membrane is selectively
permeable, which means that some
substances can pass through it while
others cannot.
Cell Membrane

 The cell membrane

is usually permeable
to substances such
as oxygen, water,
and carbon dioxide.
Cell Membrane
 On the other
hand, the cell
membrane is
usually not
permeable to
some large
molecules and
salts.
 Diffusion, Osmosis, and Active
Transport

 Substances that can move into and out of a

cell do so by one of three methods: diffusion,
osmosis, or active transport.
 Diffusion

 The main method by

which substances
move into and out of
cells is diffusion.
Diffusion
 Diffusion is the
process by which
molecules tend to
move from an area
of higher
concentration to an
area of lower
concentration.
 Diffusion
 The concentration of a substance is the
amount of the substance in a given volume.
Diffusion
 Diffusion is caused
by molecules
moving and
colliding.
 Diffusion

 The collisions
cause the
molecules to push
away from one
another and spread
out.
Diffusion
 Molecules diffuse
through the cell
membrane into a
cell when there is a
higher
concentration of
the molecules
outside the cell
than inside the cell.
 Osmosis
 The diffusion of
water molecules
through a
selectively
permeable
membrane is called
osmosis.
Osmosis
 Osmosis is
important to cells
because cells
cannot function
properly without
adequate water.
 In osmosis, water
molecules move
from an area where
they are highly
concentrated
through the cell
membrane to an
area where they
are less
concentrated.
Passive Transport
 The movement of
materials through a
cell membrane
without using
energy is called
passive transport.
 Diffusion and osmosis are both types of
passive transport.
Active Transport
 When a cell needs
to take in materials
that are in higher
concentration
inside the cell than
outside the cell, the
movement of the
materials requires
energy.
Active Transport
 Active transport is
the movement of
materials through a
cell membrane
using energy.
Active Transport
 The main
difference between
passive transport
and active
transport is that
active transport
requires the cell to
use energy while
passive transport
does not.
Active Transport
 A cell has several
ways of moving
materials by active
transport.
Active Transport
 In one method,
transport proteins
in the cell
membrane “pick
up” molecules
outside the cell and
carry them in,
using energy in the
process.
Active Transport
 Another method of
active transport is
engulfing, in which
the cell membrane
surrounds, or
engulfs, a particle.
Active Transport
 The cell must use
energy in this
process as well.
Cell Size
 Most cells are very
small.
Cell Size
 One reason is
related to the fact
that all materials
move into and out
of cells through the
cell membrane.
Cell Size
 Once a molecule
enters a cell, it is
carried to its
destination by a
stream of moving
cytoplasm.
Cell Size
 In a very large
cell, streams of
cytoplasm must
travel farther to
carry materials
from the cell
membrane to
all parts of the
cell.
Cell Size
 When a cell reaches a certain size, it divides
into two new cells.
END – 1.4
Science Explorer
Cells and Heredity

2.1 - PHOTOSYNTHESIS
2.1 - Photosynthesis - Related Video

 Calvin Cycle
 Photosynthesis
Objectives
1. What happens during the process of
photosynthesis?
2. How does the sun supply living
things with the energy they need?
Photosynthesis

 The sun
provides
almost all the
energy used
by living things
on Earth.
Photosynthesis
 All cells need
energy to carry out
their functions.
 Photosynthesis
 The process by
which a cell
captures the
energy in
sunlight and
uses it to make
food is called
photosynthesis
.
Photosynthesis
 During
photosynthesis,
plants and some
other organisms
use energy from
the sun to convert
carbon dioxide and
water into oxygen
and sugars,
including glucose.
Photosynthesis
 You can think of photosynthesis as taking
place in two stages.
Photosynthesis – 1st Stage
 The first stage of
photosynthesis
involves
capturing the
energy in
sunlight.
Photosynthesis – 1st Stage
 In plants, this
energy-capturing
process occurs in
the leaves and
other green parts
of the plant.
Pigments
 The chloroplasts in
plant cells give
plants their green
color. The green
color comes from
pigments, colored
chemical
compounds that
absorb light.
Chlorophyll
 The main pigment
found in the
chloroplasts of
plants is
chlorophyll.
 The pigments
capture light
energy and use it
to power the
second stage of
photosynthesis.
Photosynthesis – 2nd Stage
 In the second
stage of
photosynthesis, the
cell uses the
captured energy to
produce sugars.
Photosynthesis – 2nd Stage
 The cell needs two
raw materials for
this stage: water
(H2O) and carbon
dioxide (CO2).
Photosynthesis – 2nd Stage
 In plants, the roots
absorb water from
the soil.
 Carbon dioxide
enters the plant
through small
openings on the
undersides of the
leaves called
stomata.
 Photosynthesis – 2nd Stage
 The events of photosynthesis can be summed
up in a chemical equation.
Photosynthesis – 2nd Stage
 The raw materials—six molecules of carbon
dioxide and six molecules of water—are on
the left side of the equation.
Photosynthesis – 2nd Stage
 The products— one molecule of glucose and
six molecules of oxygen—are on the right
side of the equation.
Photosynthesis – 2nd Stage
 An arrow connects the raw materials to the
products.
 Photosynthesis – 2nd Stage
 Light energy, which is necessary for the chemical
reaction to occur, is written above the arrow.
Autotrophs
 A plant is an
autotroph, an
organism that
makes its own
food.
 The plant’s leaves
contain sugars
made during
photosynthesis.
Heterotroph
 A caterpillar is a
heterotroph, an
organism that
cannot make its
own food.
 To live, grow, and
perform other
functions, the
caterpillar needs
the energy in plant
sugars.
 By eating
plants,
heterotrophs get
energy from the
sun in an
indirect way.
 Nearly all living
things obtain
energy either
directly or indirectly
from the energy of
sunlight captured
during
photosynthesis.
Oxygen in the Atmosphere
 Photosynthesis
also is
essential for
the air you
breathe.
 Oxygen in the Atmosphere
 Almost all the oxygen in Earth’s atmosphere
was produced by living things through the
process of photosynthesis.
END – 2.1
Science Explorer
Cells and Heredity

2.2 - RESPIRATION
2.2 - Respiration – Related Video

◦ Anaerobic Respiration Review

◦ Cellular Respiration Electron Transport Chain
◦ Cellular Respiration Song
◦ Electron Transport System
◦ Fermentation
◦ Krebs Cycle
◦ Krebs Cycle Mitochondria
◦ Respiration and Fermentation
Objectives
1. What events occur during
respiration?
2. How are photosynthesis and
respiration related?
3. What is fermentation?
 Cells store and use
energy in a way
that is similar to the
way you deposit
and withdraw
money from a
savings account.
 When you eat a
meal, you add to
your body’s energy
savings account.
 When your cells
need energy, they
make a withdrawal
and break down
the glucose in food
to release energy.
Respiration
 The process by
which cells
“withdraw” energy
from glucose is
called respiration.
 During respiration,
cells break down
simple food
molecules such as
glucose and
release the energy
they contain.
 Because living things need a continuous
supply of energy, the cells of all living things
carry out respiration continuously.
 The term
respiration also is
used to mean
breathing, that is,
moving air in and
out of your lungs.
 To avoid confusion, the respiration process
that takes place inside cells sometimes is
called cellular respiration.
 The two kinds of
respiration are
related.
 Breathing brings
oxygen into your
lungs, and oxygen
is necessary for
cellular respiration
to occur in most
cells.
 The overall process of respiration can be
summarized in a simple chemical equation.
 However, respiration is a complex, two-stage
process.
First Stage of Respiration
 The first stage
takes place in the
cytoplasm of the
organism’s cells.
 There,
glucose
molecules
are broken
down into
smaller
molecules.
 Oxygen is not
involved in this stage
of respiration, and
only a small amount
of energy is
released.
Second Stage of Respiration
 The second stage of respiration takes
place in the mitochondria.
 There, the small
molecules are
broken down into
even smaller
molecules.
(Krebs Cycle)
 These chemical
reactions require
oxygen, and a
great deal of
energy is released.
 Two other products
of respiration are
carbon dioxide and
water.
 Photosynthesis and respiration can be
thought of as opposite Processes.
 Together, these two
processes form a
cycle that keeps
the levels of
oxygen and carbon
dioxide fairly
constant in the
atmosphere.
Fermentation

 Some cells obtain

their energy
through
fermentation, an
energy releasing
process that does
not require oxygen.
 Fermentation
provides energy for
cells without using
oxygen.
 One type of
fermentation
occurs in yeast and
some other single-
celled organisms.
 This process is
sometimes called
alcoholic
fermentation
because alcohol is
one of the products
made when these
organisms break
down sugars.
 Another type of
fermentation takes
place at times in
your body, for
example, when
you’ve run as fast
as you could for as
long as you could.
 One product of this type of fermentation is
an acid known as lactic acid.
 When lactic acid
builds up, your
muscles feel weak
and sore.
END – 2.2
Science Explorer
Cells and Heredity

2.3 - CELL DIVISION

2.3 - Cell Division – Related Video

 Cell Cycle
 Cell Division
 Cells From Other Cells
 In Cell Division – The Mitosis Song
Objectives
1. What events take place during the
three stages of the cell cycle?
2. What is the role of DNA
replication?
Cell Cycle
 The regular
sequence of
growth and
division that
cells undergo is
known as the
cell cycle.
 The cell cycle is
divided into
three main
stages.
1st Stage - Interphase

 The first stage of

the cell cycle is
called interphase.
Interphase

 During interphase,
the cell grows to its
mature size,makes
a copy of its DNA,
and prepares to
divide into two
cells.
 During the first part
of interphase, the
cell doubles in size
and produces all
the structures
needed to carry out
its functions.
Replication
 After a cell has
grown to its
mature size, the
cell makes a
copy of the DNA
in its nucleus in
a process called
replication.
 At the end of DNA
replication, the cell
contains two
identical sets of
DNA.
2nd Stage - Mitosis

 Once interphase is
complete, the
second stage of
the cell cycle
begins.
 Mitosis is the stage
during which the
cell’s nucleus divides
into two new nuclei.
 During mitosis,
one copy of the
DNA is distributed
into each of the two
daughter cells.
Mitosis Phases
 Scientists divide
mitosis into four
parts, or phases:
prophase,
metaphase,
anaphase, and
telophase.
Prophase

 During prophase,
the threadlike
chromatin in the
cell’s nucleus
begins to condense
into tiny rods.
Chromosome
 Scientists call each
doubled rod of
condensed
chromatin a
chromosome.
Chromatid
 Each identical rod,
or strand, of the
chromosome is
called a chromatid
Centromere
 The two strands
are held together
by a structure
called a
centromere.
 As the cell
progresses through
metaphase,
anaphase, and
telophase, the
chromatids
separate from each
other and move to
opposite ends of
the cell.
 Then two nuclei form around the chromatids
at the two ends of the cell.
3rd Stage - Cytokinesis
 After mitosis, the
final stage of the
cell cycle, called
cytokinesis,
completes the
process of cell
division.
 During cytokinesis, the cytoplasm divides,
distributing the organelles into each of the
two new cells.
 Each daughter cell
has the same
number of
chromosomes as
the original parent
cell.
 At the end of
cytokinesis, each
cell enters
interphase, and the
cycle begins again.
 How long it takes
a cell to go
through one cell
cycle depends
on the type of
cell. The length
of each stage in
the cell cycle
also varies.
 A cell makes a copy
of its DNA before
mitosis occurs.
 DNA replication
ensures that each
daughter cell will
have all of the
genetic information
it needs to carry
out its activities.
 The two sides of
the DNA ladder are
made up of
alternating sugar
and phosphate
molecules.
 Each rung of the DNA ladder is made up
of a pair of molecules called nitrogen
bases.
Nitrogen Bases - ATGC

 There are four

kinds of nitrogen
bases: adenine,
thymine, guanine,
and cytosine.
 Adenine only pairs
with thymine, and
guanine only pairs
with cytosine.
 DNA replication
begins when the
two sides of the
DNA molecule
unwind and
separate.
 Next, nitrogen
bases in the
nucleus pair up
with the bases on
each half of the
DNA molecule.
 Once the new
bases are
attached, two new
DNA molecules are
formed.
 The order of the
bases in each new
DNA molecule will
exactly match the
order in the original
DNA molecule.
END 2.3
Science Explorer
Cells and Heredity

2.4 - CANCER
2.4 - Cancer - Related Video
 3D Medical Animation – What is Cancer?
 Cancer Cells vs Healthy Cells
 Cancer Growth Animation
 DNA Mutation
 Gene Mutation
 Mitosis in Cancer
Objectives
1. How is cancer related to the cell cycle?
2. What are some ways that cancer can
be treated?
 Cancer is a
disease in which
cells grow and
divide
uncontrollably,
damaging the parts
of the body around
them.
 There are more than 100 types of cancer.
 Cancer can occur in almost any part of the
body.
 Cancers are often named by the place in the
body where they begin.
 In the United
States today,
lung cancer is
the leading
cause of
cancer deaths
among both
men and
women.
 Scientists think that
cancer begins
when something
damages a portion
of the DNA in a
chromosome.
 The damage
causes a change in
the DNA called a
mutation. Cancer
begins when
mutations disrupt
the normal cell
cycle, causing cells
to divide in an
uncontrolled way.
 Without the
normal
controls on the
cell cycle, the
cells grow too
large and
divide too
often.
 As the cell divides, more and more
abnormal cells like it grow near it.
 In time, these cells
form a tumor.
 A tumor is a mass
of abnormal cells
that develops when
cancerous cells
divide and grow
uncontrollably.
 Some of the
cancerous cells
may break off the
tumor and enter
the bloodstream.
 In this way, the
cancer can spread
to other areas of
the body.
 Doctors usually
treat cancer in one
or more of three
ways: surgery,
radiation, or drugs
that destroy the
cancer cells.
 When a cancer is
detected before it
has spread to other
parts of the body,
surgery is usually
the best treatment.
 If doctors can completely remove the
cancerous tumor, a person may be cured
of the disease.
 If, however, the
cancer has spread
or the tumor cannot
be removed,
doctors may use
radiation.
 Fast growing
cancer cells are
more likely than
normal cells to be
destroyed by
radiation.
 Chemotherapy is
the use of drugs to
kill cancer cells.
 It is effective
because the drugs
spread throughout
the body, killing
cancer cells or
slowing their growth.
 Unfortunately, none
of these cancer
treatments is
perfect.
 Most have
unpleasant, or
even dangerous,
side effects.
 Scientists continue
to look for new
ways to treat
cancer.
 Scientists estimate
that almost two
thirds of all cancer
deaths are caused
either by tobacco
use or unhealthful
diets.
 Smoking is the main cause of lung
cancer.
 Unhealthful diets
may lead to almost
as many cancer
deaths as does
tobacco.
 A diet that is low in
fat and includes a lot
of fruits, vegetables,
and grain products
can help lower a
person’s risk of
some types of
cancer.
END 2.4