Transcript Cell Structure and Function - Mrs. Gann`s 6th grade class

Cell Structure
and Function
Chapter 2
What do cells do?
Plant cells and Animal cells
A single cell is the smallest structure that
carries out the activities necessary for life. A cell
is like a tiny factory. Different parts of the factory
produce or control different things. One part
gets food or water. Another part keeps the cell
clean. Still other parts are in charge of
reproducing. All parts of the cell must work
together to run smoothly. An organism cannot
survive without cells doing their work.
Animal and plant cells may look
different but they share many similar
features. They have at least 3 features in
common: cell membranes, a nucleus
and cytoplasm. Look at txt. Pg. A47
The cell membrane is the outer
covering of the cell. Water and food enter
through the cell membrane, and wastes
leave through it. Plant cells have an
additional structure called the cell wall
which gives them extra support.
Each animal cell and plant cell contains
a nucleus. The nucleus is the control
center for the cell. It carries information
for reproduction and directs all cell
activities.
The cytoplasm is a gel-like material
that surrounds all parts of the cell within
the membrane, including the nucleus and
the organelles.
Organelles are small structures, each of which has
a specific job.
Cell structure
Function
Mitochondria
Vacuoles
Nucleus
Provide energy
Store materials
Cell control center;
reproduction
Cell membrane
Structure and transport
Golgi Bodies &
transport
Endoplasmic Reticulum
The nucleus is the cells control center
and acts during reproduction. The cell
membrane gives the cell structure and
transports materials into and out of the
cell. The Golgi Bodies and Endplasmic
Reticulum transport materials with the cell.
Cell transportation
A cell membrane is a special kind of
barrier. It holds important cell materials
inside it, but allows water, gases, and
wastes to pass through.
In passive transport, materials move
into or out of the cell without the cell using
any energy. The simplest kind of passive
transport is diffusion.
Substances diffuse from regions of high
concentration to regions of low concentration.
Sometimes a cell needs to move materials
opposite the way diffusion would move them. In
active transport, substances move from regions
of low to high concentration. This requires the
cell to use its own energy.
Sometimes large proteins in the cell
membrane help move materials in and out. The
proteins act as tunnels to allow only certain
materials to pass.
Using Energy
All living things need energy to survive.
Plants use a process called
photosynthesis to make food by
harnessing the energy from sunlight. This
process takes place in chloroplasts, and
depends on the green pigment chlorophyll.
During photosynthesis, water from the
ground is combined with carbon dioxide
from the air. Oxygen is produced and
released into the air. A molecule of
glucose is also produced. Glucose is one
of the high energy compounds called
sugars.
All plants and animals depend on the
sugars made by the plants for their food.
They get energy from the sugars by the
process of cellular respiration.
All plants and animals depend on the
sugars made by the plants for their food.
They get energy from the sugars by the
process of cellular respiration.
Mitochondria perform cell respiration,
the reverse process of photosynthesis.
This process combines oxygen from the
air with glucose from food to form water
and carbon dioxide. A lot of energy is
released in the process
Mitochondria store this energy in a
molecule called ATP. This molecule acts
like a battery. The cell tap into ATP
whenever it needs to use energy.
Cell Division
New organisms usually begin when
cells from two parents combine to form a
new cell. Soon the single cell divides to
form two cells. The two divide to form
four, and the four divide into eight cells.
Millions of divisions occur as the cells
become a complete organism.
As cells divide, they differentiate, which
means they become different from one
another. Early on the cells organize
themselves into three groups, called germ
layers. One layer will form the skin and
nerves. Another layer becomes the lining
of the digestive tract. The third layer
becomes all the other body parts
Bacteria and other single-celled
organisms can also copy themselves.
This copying results in new individuals.
When conditions favor division, a bacterial
colony can double very quickly.
Lesson 2 Specialized Cells
Different cells for different Job
All multicellular organisms have
specialized cells that work together. Both
plants and animals have tissues that
perform specific jobs. Most complex
organisms have a variety of tissues.
Epithelial tissues are sheets of cells
that cover surfaces. They also line certain
body cavities and blood vessels.
Connective tissue, as the name
implies, joins other tissues together. It
also stores fat and make of specialized
cells and fibers that stick to living cells.
Bone is a type of connective tissue too.
All muscle tissue creates movement in
one direction only, either by getting longer
or shorter.
Electrical impulses that constantly run
through your body are produced and
routed by nervous tissue.
Organs are made up of several tissue
types that work together to perform one or
more functions.
The brain, heart, and liver are three
human organs. Some organs, like
kidneys, perform more than one function.
Kidneys remove waste from the body and
also help control blood pressure.
Organ Systems
The more complex the organism, the
greater the number of organ systems that
are needed to carry out life processes.
Humans have 11 organ systems. The
systems also influence one another.
Some organs work for more than organ
system.
Urinary System
This system helps regulate the amount of
water and salt in the blood, as well as
removing liquid wastes.
Musculoskeletal system
Supports all parts of your body and
allows you to move different parts of your
body. Bones anchor other body parts and
provide the structure needed for
movement
Contracting your muscles makes your
body parts move. The muscles also
generate warmth for your body.
Nervous System
Your brain is an indispensable organ, the
headquarters of the nervous system. All
your senses feed information into the
brain. The brain processes and responds
to this information, often responding by
sending signals down nerves to muscles.
The brain also controls the other organ
systems. Look at txt. Pg. A57
Four of the remaining organ systems
help your body fight infection, and
allow you to eat, breathe, and
reproduce. Another system produces
hormones that regulate many body
functions.
Endocrine System
Your body’s endocrine system works like a
chemical messenger system. The glands
of the endocrine system act as a
communication centers. Endocrine glands
are a specialized group of cells that make
and send out hormones. Hormones act as
messages. They travel through the blood
stream and are picked up only by certain
cells.
Humans use about 50 different
hormones. Some help regulate growth
and energy use. Others control blood
sugar, minerals, and other chemicals.
Some hormones cause specific
changes in the body.
Many plants use hormones, too. These
may cause a stem to bend toward the
light, or could direct a plant to grow
taller instead of wider.
Gland
Function
Pituitary Gland
This gland in the brain makes at
least 8 different hormones. Many
control other glands.
Thyroid gland
This helps regulate the body’s use
of energy.
Thymus
This gland helps the body’s
immune system.
Adrenal Glands
These manufacture hormones that
regulate glucose & respond to
stress. They also influence
reproductive hormones.
Pancreas
This produces insulin and other
hormones that affect the level of
blood sugar. Lack of insulin leads
to a disease called diabetes.
Lesson 3
How does disease affect
cells?
Cells and Diseases
Causes of Diseases
Many things can cause illness or disease.
Some diseases result when the body is
invaded by alien organisms or viruses.
Other diseases result when body
systems do not function properly.
Infectious Diseases
Infectious diseases are caused by harmful
organisms or viruses. Bacteria & some
types of fungi are common types of
infections. Certain types of worms can
lodge in the intestines or muscles, causing
several serious diseases. Protozoa
carried by mosquitoes cause malaria.
Contagious diseases can be spread easily from
one person to another. Other diseases, like
those from food poisoning, are not contagious.
Viruses are not living organisms because they are
not made of cells. Viruses are common causes
of infectious disease. Viruses contain generic
instructions that take over a cell’s normal
instructions. Typically, the virus instructs the cell
to male more viruses.
Many viral diseases are mild, like colds, the flu, &
chicken pox. Other viruses are more dangerous
or even deadly. Viral diseases such as hepatitis
or AIDS have killed many people.
Non-infectious Diseases
Non-infectious diseases occur when a body
system does not function properly. These
types of diseases cannot spread from
person to person. Sometimes the
diseases are caused by a condition that is
inherited.
Other times the diseases appears as a
person’s body ages. Healthy lifestyles and
habits can help prevent many of these
later-in-life diseases.
Poor nutrition causes many non-infectious
diseases. People who do not receive the
proper vitamins in their food can suffer a
variety of illnesses and impaired organ
functions.
Fighting Disease
Your body has 3 main lines of defense
against invasion by disease agents. The
first line of defense is made up of your
body’s physical and chemical barriers.
These include your skin, tears, salvia,
earwax, and mucus.
Your body’s second line of defense consists
of processes that kick in should harmful
agents enter.
One of these defenses is inflammation. The
blood releases fluid and other products
that enlarge the area and make it red and
sore.
The second line of defense can include the
production of special cells called
phagocytes. These cells surround and
consume harmful disease agents that
invade your body. Phagocytes are one
type of white blood cells.
The body has a very powerful defense
weapon to fight specific harmful
agents of disease. It’s called the
immune system. And is your body’s
3rd line of defense.
Immune System
The immune system uses special cells that
travel throughout the body & recognize
invading pathogens. These cells can
recognize harmful invaders because they
have surface structures different from
those of normal body cells.
Certain types of white blood cells produce
special proteins called antibodies that
also fight invaders.
After the body destroys invaders, the body
begins to recover from illness. As an
added benefit, some of the immune
system’s special white blood cells remain
in the body. If the same pathogens invade
the body again, these cells can
immediately produce the needed
antibodies. This means that the body is
now immune to, or protected from that
particular illness.
Disease Prevention or Treatment
Many diseases that were once deadly are now
under control. Fro example, smallpox killed
hundreds of millions throughout history. Yet in
1980, the World Health Organization declared
smallpox to be eradicated, meaning it was wiped
out.
A vaccine usually contains an inactive version of a
pathogen. When the body is exposed to the
vaccine, it slowly makes antibodies against it.
Later, should the real pathogen enter the body,
the antibodies are ready right away to stop it.
Penicillin is an antibiotic that works by
weakening the cell walls of bacteria,
allowing water from outside to rush
inside.