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Discovering Cells
Cell
• Pronunciation: (How to say it) [Sel]
• Definition: Basic organizational unit of
structure (how it’s built) and function (how it
works) in living organisms. (Organism =
living thing.
• Cells form the parts of an organism and
carry out all of an organism’s processes, or
functions.
Cells form all the parts of our bodies and
carry out all the jobs different parts of our
bodies have to do.
Carrying messages
Cells are very tiny, and
most individual cells
can only be seen with a
microscope.
http://learn.genetics.utah.edu/content/begin
/cells/scale/
The invention of the microscope made it
possible for people to discover and learn
about cells.
Cells & Structure
Living things are built differently because of
the different kinds of cells they have and
the different ways their cells are put
together. The way a body is built
determines how it works.
Cells and Function
Cells do all the
different jobs our
bodies need,
carrying out a wide
range of functions,
like…
Cells in Our Bodies Do This Job
Maintaining chemical concentrations
Cells in Our Bodies Do This Job
Expelling (getting rid of) wastes
Cells in Our Bodies Do This Job
Ingesting food
Cells in Our Bodies Do This Job
Responding to the environment
Cells in Our Bodies Do This Job
Growing
Cells function similarly in all organisms,
doing the same kinds of jobs no matter
what kind of living thing they’re in.
Robert Hooke
Named cells when looking at a thin slice of
cork through a compound microscope he
made himself.
Anton van Leeuwenhoek
Also made his own simple microscope and
observed living cells from pond water and
scrapings from teeth (bacteria in plaque)
Matthias Schleiden
All plants are made of cells
Theodor Schwann
All animals (and all living things) are made
of cells
Rudolf Virchow
All cells come from other cells
Cell Theory
• Pronunciation: [Sel theer-ee]
• Definition: Widely accepted explanation of
the relationship between cells and living
things
• Parts of cell theory:
– All living things are composed or made of cells
– Cells are the basic unit of structure and function
in living things
– All cells are produced from pre-existing cells
Cells function similarly in all organisms.
Regardless of the organism they are a part
of, cells carry out the basic processes of
life in similar ways. Organisms may be
composed of one cell or many trillions of
cells
Unicellular
• Pronunciation: [you-knee-SELyuh-ler]
• Uni=one
• Definition: Single-celled or made
of one cell
Multicellular
• Pronunciation: [muhl-teeSEL-yuh-ler]
• Multi = many
• Definition: Composed or
made of many cells
Differentiation
As multicellular organisms develop, their cells differentiate.
This means that their cells become different, and that the
shape of the cell is linked to its specialized function, or
the job it does.
Differentiation
Cells take on specialized functions; some
become the heart, brain, etc.
After Differentiation
After differentiation,
most cells lose the
ability to become
another type of cell.
Nerve Cell Specialization
The long, fingerlike extensions of the nerve
cell help transmit information from one part
of your body to another.
Blood Cell Specialization
Red blood cells carry oxygen throughout
your body. Their flattened shape enables
them to fit through tiny blood vessels.
Cells: Organizational Units
In multicellular organisms,
cells are often organized
into differentiated tissues,
organs, and organ systems
with specialized functions
Tissue
• Pronunciation: [tish-oo]
• Definition: a group of similar cells that
work together to perform a specialized
function
• Examples: muscle tissue, nerve tissue
Brain
The brain is made of nervous tissue, which
consists of nerve cells.
Organ
• Pronunciation: [ore-gun]
• Definition: Made of different kinds of tissues
that work together
• Example: Brain contains other types of
tissues, like blood vessels and the
connective tissue that protects the brain
Other Organs
Heart, liver, and kidneys
Organ System
• Pronunciation: [ORE-gun-SIStem]
• Definition: Group of organs
that work together to perform
a major function or job
• Examples: Brain is part of
nervous system, which directs
body activities and processes
Other Organ Systems
• Musculoskeletal
• Digestive
• Circulatory
Organ systems function because of the
contributions of individually specialized
organs, tissues, and cells. The failure of
any part can affect the entire system.