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Cells:
The Basic Units of Life
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Cells
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Tissues
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Organs
Organ
Systems
Organisms
Cells
• Every living thing has at least one cell.
– Some have only one and some have trillions.
– Most cells are to tiny to be seen without a
microscope.
– A chicken egg is one of the largest cells.
– Not all cells look or act the same.
– You have 200 different kinds of cells: blood cells,
bone cells, muscle cells …………
Tissues
• A tissue is a group of cells working together to
perform a specific job in the body. The
material around and between the cells is also
part of the tissue.
– Examples of tissue: red blood cells, fat, and
muscle
Organs
• When two or more tissues work together to
perform a specific job, the group of tissues is
called an organ.
– Examples of organs: stomach, heart, intestines,
heart, lung, and skin
• Plants also have different kinds of tissues that
work together. A leaf is a plant organ that contains
tissue that traps light energy to make food.
Examples of plant organs: stem and roots
The Skin
• The skin is the body’s largest organ. An
average-sized person’s skin has a mass of
about 4.5 kg (almost 10 pounds!).
Brain Food
• The part of the skin, hair, and nails that we can
see is DEAD tissue. Isn’t it strange that we put
so much effort into making sure our dead cells
look nice?
Organ Systems
• Organs work together in groups to perform
particular jobs. These groups are called organ
systems.
• Each system has a specific job to do in the
body.
– Examples:
• digestive system breaks down food to use by your
body’s cells
• nervous system transmits information back in forth
between the brain and other parts of the body
There are 11 main organ systems.
• The organs in the organ system depend on each
other. If any part of the system fails, the whole
system is affected. And failure of one organ
system can affect other organ systems.
• Main organ systems : integumentary system,
skeletal system, muscular system, nervous
system, endocrine system, cardiovascular system,
lymphatic system, respiratory system, digestive
system, urinary system, reproductive system
Organism: Independent Living
• Anything that can live on its own is called an
organism.
• All organisms are made up of at least one cell.
– organisms made up of one cell – unicellular
– organisms made up of groups of cells –
multicellular
The Big Picture
• Although unicellular and multicellular organisms can live
on their own, they usually do not live alone. Organisms
interact with each other on many different ways.
– Populations – groups of organisms that are of the same kind and
that live in the same area
• Example – all the white tail deer in the forest
– Communities - two or more different populations living in the
same area
• All the populations combined in the forest (deer, rabbits, snakes, etc..)
– Ecosystems – all the communities and all the nonliving things
that affect it, such as water, soil, rocks, temperature, and light
• Ecosystems on land – terrestrial ecosystems
• Ecosystems in water – aquatic ecosystems
Discovery of Cells
Seeing the first cells
• 1665 - Robert Hooke – British scientist – used
cork (soft plant tissue found in the bark of a tree)
– He saw tiny boxes and called them cells.
• 1673 – Anton van Leeuwenhoek – Dutch
merchant – used a handmade microscope to look
at pond scum – He saw many small creatures. He
also looked at blood from animals and teeth
scrapings. First to see bacteria and discovered
that yeast is a unicellular organism.
The Cell Theory
Matthias Schleiden – 1838 – all plant parts are
made of cells
Theodore Swann – 1839 - wrote the first part of
the cell theory.
o All organisms are composed of one or more cells.
o The cell is the basic unit of life in all living things.
1858 – Rudolf Virchow – wrote the third part of
the cell theory
o All cells come from existing cells
• All cells have:
– Cell membrane- surrounds all cells; acts as a barrier
between the inside of the cell and its environment;
controls what comes in and what goes out
– Hereditary material – cells receive a copy of hereditary
material (DNA) It controls all of the activities of the cell
and contains the information needed for that cell to make
new cells
– Organelles – structures within a cell that allow it to live,
grow, and reproduce
– Cytoplasm – fluid that surrounds the organelles within a
cell
– Small size – almost all cells are too small to see with the
naked eye
Amoebas
• An amoeba is a single celled (unicellular)
organism. It cannot get large enough to be seen.
As a cell gets larger, it needs more food and
produces more waste. Therefore more material
must be able to move in and out through the cell
membrane.
• To keep up with these demands, a growing cell
needs a larger surface area through which to
exchange materials. As the cell’s volume
increases, its outer surface grows too.
• Go to page 12 to help explain!!!
• Surface-to-Volume Ratio
Benefits of being Multicellular
• A single cell as big as you would have an
incredibly small surface-to-volume ratio and
would not survive because its outer surface
would be too small to allow in the materials
needed.
• Multicellular organisms grow by producing
MORE cells, not LARGER cells.
– An elephant has more cells than you, not larger
cells.
Many kinds of cells
• Having many different cells that are specialized
for specific jobs allows multicellular organisms to
perform more functions than unicellular
organisms.
• Different kinds of cells can form tissues and
organs with different functions.
• Some specialized cells: muscle cells, eye cells,
brain cells….
• Be glad you are not UNICELLULAR! How boring!
Two types of cells
Prokaryotic Cells
• Also called bacteria
• World’s smallest cells
• No nucleus
• Circular DNA (shaped like a
rubber band)
• No membrane-covered
organelles
Eukaryotic Cells
• More complex
• All other cells
• Have a nucleus
• Have membrane-covered
organelles
• Linear DNA stored in the
nucleus
Eukaryotic Cells
Animal Cells
1. Nucleus
2. Ribosomes
3. Cell Membrane
4. Endoplasmic Reticulum
5. Lysosomes
6. Mitochondria
7. Golgi Complex
Plant Cells
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Nucleus
Ribosomes
Cell Membrane
Endoplasmic Reticulum
Lysosomes
Mitochondria
Golgi Complex
Cell Wall
Large Vacuole
Chloroplast
The Cell's Command Center -- The
Nucleus
• Largest and most visible organelle in a eukaryotic cell
• Surrounded by a nuclear membrane for protection
• Stores DNA that has information on how to make all
the cell’s proteins (almost all chemical reactions
important to the cell’s life involve protein)
Read more: List of Organelles | eHow.com
http://www.ehow.com/info_8642034_listorganelles.html#ixzz23M2NtNGk
The Energy Plant -- Mitochondria
• ATP (molecule that supplies energy to fuel the
cell’s activities) made here from food
molecules
• Bean shaped – surrounded by two
membranes
• Must have oxygen
• Highly active cells (such as heart and liver)
have thousands
Manufacturers -- Ribosomes
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Make protein chains out of amino acids
Smallest but MOST abundant organelle
Not covered with a membrane
ALL cells have ribosomes (prokaryotes
included)
The Cell’s Delivery System –
Endoplasmic Reticulum
• Membrane-covered compartment that makes
lipids and other materials for use inside and
outside the cell
• Breaks down drugs and other damaging
chemicals
• Internal delivery system
• Looks like flattened sacks stacked side by side
Shipping– Golgi Complex
Packaging -Vesicles
• Looks like the ER but is located closer to the
cell membrane
• Modifies lipids and proteins from the ER and
delivers them to other parts of the cell or
outside the cell
• Vesicles are pieces of the golgi complex that
pinches off and stores the final products
Trash Collector -- Lysosomes
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Specialized vesicles in animal cells
Contain enzymes
Destroy worn-out or damaged organelles
Get rid of waste materials and protect the cell
from foreign invaders
• If the membrane of a lysosome opens, the
enzymes will spill out into the cell and kill the
cell. (How a tadpole loses its tail)
Plant Cells -- Chloroplasts
• Only found in plants and algae
• Energy-converter
• Has two membranes and structures like stacked
coins and contains chlorophyll – which makes the
chloroplast green
• Chlorophyll traps the energy from sunlight and
uses it to make sugar in the process
photosynthesis.
• Mitochondria then use the sugar to make ATP.
Cell Wall
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Found in plant cells
Outside the cell membrane
Made of cellulose (sugar)
Provides strength and support to cell
membrane
Water cooler- Vacuoles
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Most plant cells have very large vacuoles.
Membrane-covered
Stores water and other liquids
When full, helps support the cell
When empty, the cell shrivels (causing the
plant to wilt)