3. Cells
• Every living thing has at least one cell.
– Some have only one and some have trillions.
– Most cells are too 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 …………
4. Tissues
• A tissue is a group of cells working together to
perform a specific job in the body.
– Examples of tissue: red blood cells, fat, and
muscle
5. 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,
liver, 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
6. 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!).
7. 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?
8. 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
9. 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.
• Examples: skeletal system, muscular system,
nervous system, endocrine system,
cardiovascular system, respiratory system,
digestive system
10. 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
11. 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 – Nilgiri langur
– Communities - two or more different populations living in the
same area
• All the populations combined in the forest (Monkey)
– 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
14. 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.
15. Early discoveries
• 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.
16. 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
17. • 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
18. 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!
19. Dutch scientist Antonie van Leeuwenhoek
detected other hidden, minuscule organisms—
bacteria and protozoa. It was unsurprising that
van Leeuwenhoek would make such a discovery.
He was a master microscope maker and perfected
the design of the simple microscope (which only
had a single lens), enabling it to magnify an object
by around two hundred to three hundred times its
original size. What van Leeuwenhoek saw with
these microscopes was bacteria and protozoa, but
he called these tiny creatures “animalcules.”
20. Van Leeuwenhoek became fascinated.
He went on to be the first to observe and
describe spermatozoa in 1677. He even
took a look at the plaque between his
teeth under the microscope. In a letter to
the Royal Society, he wrote, "I then most
always saw, with great wonder, that in
the said matter there were many very
little living animalcules, very prettily a-
moving.”
21. In the nineteenth century, biologists began taking a
closer look at both animal and plant tissues,
perfecting cell theory. Scientists could readily tell
that plants were completely made up of cells due to
their cell wall. However, this was not so obvious for
animal cells, which lack a cell wall. Many scientists
believed that animals were made of “globules.”
22. German scientists Theodore Schwann and
Mattias Schleiden studied cells of animals and
plants respectively. These scientists identified
key differences between the two cell types
and put forth the idea that cells were the
fundamental units of both plants and animals.
However, Schwann and Schleiden misunderstood
how cells grow. Schleiden believed that cells
were “seeded” by the nucleus and grew from
there. Similarly, Schwann claimed that animal
cells “crystalized” from the material between other
cells. Eventually, other scientists began to
uncover the truth. Another piece of the cell theory
puzzle was identified by Rudolf Virchow in 1855,
who stated that all cells are generated by existing
cells.
23. At the turn of the century, attention began to
shift toward cytogenetics, which aimed to link
the study of cells to the study of genetics. In the
1880s, Walter Sutton and Theodor Boveri were
responsible for identifying the chromosome as
the hub for heredity—forever linking genetics
and cytology. Later discoveries further
confirmed and solidified the role of
the cell in heredity, such as James Watson and
Francis Crick’s studies on the structure of DNA.
24. The discovery of the cell continued to impact science
one hundred years later, with the discovery of stem cells,
the undifferentiated cells that have yet to develop into
more specialized cells. Scientists began deriving
embryonic stem cells from mice in the 1980s, and in
1998, James Thomson isolated human
embryonic stem cells and developed cell lines. His work
was then published in an article in the journal Science. It
was later discovered that adult tissues, usually skin,
could be reprogrammed into stem cells and then form
other cell types. These cells are known as induced
pluripotent stem cells. Stem cells are now used to treat
many conditions such as Alzheimer’s and heart disease.
25. Today, scientists are working on personalized
medicine, which would allow us to grow stem
cells from our very own cells and then use
them to understand disease processes. All of
this and more grew from a single observation
of the cell in a cork.
26. Two types of cells
Prokaryotic Cells
• 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
28. 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)
29. 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
thousand
• Powerhouse of the cell
30. Protein Factory -- Ribosomes
• Make protein chains out of amino acids
• Smallest but MOST abundant organelle
• Not covered with a membrane
• ALL cells have ribosomes (prokaryotes included)
31. 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
32. 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
33. Trash Collector -- Lysosomes
• 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)
34. 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.
35. Cell Wall
• Found in plant cells
• Outside the cell membrane
• Made of cellulose (sugar)
• Provides strength and support to cell
membrane
36. Water cooler- Vacuoles
• 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)
