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Cells
The Building Blocks of Life
Cells
• Cell: The smallest unit of an organism that
can carry on life functions.
• They grow, reproduce, use energy, and
respond to stimuli.
Blood cells
Muscle cells
Nerve cells
I. Cells
• Robert Hooke discovered and named cells
in 1665.
A thin slice of cork
showing cells
I. Cells
• 10 years later in 1675, Anton van
Leeuwenhoek first observed bacteria and
protozoa.
I. Cells
• The nucleus was not described until 1833
I. Cells
• DNA was not described until the 1950’s.
Why did it take so long to make
these discoveries?
Scratch and sniff paper
x1000
Staple in paper x35
Mascara brush x35
Mosquito head x200
http://www.mos.org/sln/SEM/sem.html
II. Types of Cells
• Some organisms are only one cell big.
diatoms
paramecium
protozoa
II. Types of Cells
• Some organisms are made of millions or
billions of cells working together.
II. Types of Cells
• Prokaryotic-cells that have no membrane
(“skin”) bound internal structures (bacteria)
II. Types of Cells
• Eukaryotic-cells with membrane (“skin”)
bound internal structures (protists, fungi,
plants, and animals)
Which cell is
which?
Prokaryotic
or
Eukaryotic?
III. Cell Organization
• In a single celled organism, the cell has to
do all of the life functions by itself.
Division
(reproduction)
Eating (using energy)
III. Cell Organization
• In a multicellular organism, each cell is
assigned a specific job. Together, they
make the organism complete.
Blood, nerve, and muscle cells
working together make our heart
complete.
III. Cell Organization
• Within each cell, there are small structures
that help the cell do its job, they are called
organelles. (tiny organ)
IV. Organelles
• Cell Membrane: Protective outer covering
for plant and animal cells. It controls what
moves into and out of the cell. (revolving
door)
IV. Organelles
• Cytoplasm: Supportive, gelatin-like
structure found inside plant and animal
cells. Helps maintain cell shape. (jell-o)
IV. Organelles
• Nucleus: Directs all cell activities in plant
and animal cells. It also holds a copy of the
chromosomes for the organism. (coach)
IV. Organelles
• Chromosomes: Found inside the nucleus,
they contain the DNA which holds all of
your hereditary information. (play-book)
IV. Organelles
• Nucleolus: Found inside the nucleus, it
manufactures ribosomes. (ribosome factory)
IV. Organelles
• Ribosomes: Makes proteins for cells.
(protein factory)
IV. Organelles
• Endoplasmic Reticulum (ER): Helps
transport materials around the cell.
(hallway)
IV. Organelles
• Golgi Apparatus/Bodies: Sorts, packages,
and mails proteins around the cell. (post
office)
IV. Organelles
• Lysosomes: Contains digestive enzymes
(acids) to help break down food, wastes,
and worn out cell parts. (recycler)
Lysosomes “eat” the tadpole tail.
IV. Organelles
• Mitochondria: breaks down food into
energy for the organism. (batteries)
Which type of cell would have more
mitochondria? Why?
• Muscle cells or fat cells?
IV. Organelles
• Vacuole: Storage containers for food, water,
or waste. Plant cells have one large
vacuole. (lunchbox)
Plants with empty vacuoles have
limp leaves and stems
IV. Organelles
• Cell Wall: Outermost covering of a plant
cell. Provides protection and support for
the plant. (brick wall)
Humans do not have the right
digestive enzymes to break down the
cellulose in cell walls
IV. Organelles
• Chloroplasts: In plants cells only, it converts
sunlight into food. Chlorophyll inside the
chloroplasts gives plants their green color.
(solar panel)
Organelles all work together to make
a cell function
Cells work together to form the
whole organism
V. Levels of Organization in Biology
1 Cells
2 Tissue
3 Organs
4 Organ System
5 Organism
These levels continue through
ecology
5. Organism
6. Population
7. Community
8. Ecosystem
9. Biome
10. Biosphere
VI. Cell Theory
A collection of ideas that forms the foundation
for all biology.
Equivalent to the Theory of Gravity (Physics),
Atomic Theory (Chemistry), and Theory of
Evolution (Evolutionary Biology)
VI. Cell Theory
1. All living things are made of one or more
cells.
VI. Cell Theory
2. Cells are the basic units of structure and
function in living things. (The building
blocks of life)
VI. Cell Theory
3. Living cells only come from other living
cells.