Chapter 3 ~ Cells: The Basic Units of Life
The Diversity of Cells:
Cells
Cell Theory
Robert Hooke
Cells
Anton Van
Leeuwenhoek
Protists
 All living things are made of cells. Cells are the
smallest unit that can perform all the processes
necessary for life.
Cell and Cell Theory:
 Robert Hooke ~ 1st person to describe cells
o 1665 he built a microscope to look at tiny
objects
o One day looked at a thin slice of cork (comes
from the bark of a cork tree) – looked like it
was made of little boxes
 He named these cells ~ which means “little
rooms” in Latin
 He also looked at thin slices of living plants
(these cells were ‘juicy’) among other
things
 Plant cells have cell walls which make
them easy to see; at first he didn’t
think that animals had cells because
he couldn’t see them
 Anton Van Leeuwenhoek ~ a Dutch merchant
o 1673 made his own microscope and looked at
pond scum
 He found the tiny organisms we now call
protists
 He also looked at animal blood
 Fish, bird and frog blood cells are oval
 Human and dog blood cells are flat
and round
 He was also the first person to
CELL
THEORY –
all three
parts!
Mathias
Schleiden
Theodor
Schwann
Rudolf
Virchow
see bacteria!
Cell Theory
(200 years later…) Mathias Schleiden studied plants
 1838 – concluded all plant parts were made of cells
Theodor Schwann – studied animals
 1839 – concluded all animal parts were made of cells
o Wrote the 1st two parts of the Cell Theory
 1. All organisms are made of 1 or more
cells
 2. The cell is the basic unit of all living
things
Rudolf Virchow – stated the 3rd part of the Cell
Theory
 1858 – 3rd part of Cell Theory
 3. All cells come from existing cells.
Cell Size
 Most cells are too small to be seen with the naked
eye. It would take 50+ human cells to cover the dot
on this i ~ WOW!
 There are a few very large cells
o The yolk of a chicken egg ~ it can be this big
because they do not have to take in more
nutrients!
But why are cells so small?
Small cell
size
Surface
area-tovolume
ratio
 Physically, cells have to take in food and get rid of
wastes through the cell membrane
o As a cell gets bigger, it needs more food and
produces more waste
o *** As a cell’s volume goes up, its surface area
becomes too small to take in enough nutrients
or pump out enough waste
 Surface area-to-volume ratio
surface area
Volume
Parts of a Cell
Cell
membrane
Cell membrane ~ a phospholipid protective layer that
covers the cell’s surface and acts as a barrier
 Controls material going in and out of a cell
 Inside the cell is a fluid called cytoplasm
Cytoplasm
Organelle
Nucleus
Organelles – small bodies in a cell’s cytoplasm that
are specialized to perform specific functions in the
cell
 Genetic material – all cells contain DNA
 In some cells, the DNA is enclosed in an organelle
called the nucleus
There are two kinds of cells:
Prokaryote
Eubacteria
Archaebacteria
Eukaryote
 1. Prokaryotic cells – have no nucleus, singlecelled organism
o Two types of prokaryotic cells
 Eubacteria
 Common bacteria
 No nucleus, but do contain DNA
 Have a cell wall
 Archaebacteria
 Single-celled
 Some live in very unusual places
(Yellowstone Park)
They are called
o Heat-loving
extremophiles.
o Salt-loving
o Methane-making
 Volcanic vents in the ocean
 2. Eukaryotic cells – largest cells (10x’s larger
than most bacteria)
o Have a nucleus that contains the cell’s
DNA
o Have many organelles
Organelles:
Nucleus
Nucleolus
Ribosome
Endoplasmic
reticulum
Smooth ER
Rough ER
Mitochondria
Chloroplasts
Photosynthesis
Chlorophyll
1. Nucleus – holds a cell’s DNA – 2 membranes
2. Nucleolus – inside the nucleus; makes
ribosomes
3. Ribosome – make proteins; smallest organelle
a. Not membrane-bound
b. Some float freely in cytoplasm, some are
attached to the endoplasmic reticulum
4. Endoplasmic reticulum (ER) (like the
highway of the cell)
a. tubes and passageways for transporting
materials to different places in the cell
b. smooth ER – no ribosomes attached
c. rough ER – ribosomes attached
i. ribosomes make proteins that the ER
delivers throughout the cell
5. Mitochondria (the power plant of the cell)
a. Main power source of the cell
b. Sugar is broken down to produce energy
c. Covered by 2 membranes
d. In most cells, ATP (energy) is made in the
mitochondria
6. Chloroplasts (plants)
a. Photosynthesis takes place in
chloroplasts
i. Uses sunlight and water to make
sugar and oxygen
b. Green color is from chlorophyll which
traps the energy of the sun
Golgi
complex
Cell wall
Cell
membrane
Hydrophobic
Hydrophilic
7. Golgi Complex – (like the UPS store)
a. Packages and distributes proteins
b. The membrane of the Golgi pinches off
with materials inside that need to be
transported
8. Cell wall (plants, algae and fungi)
a. Rigid structure that gives support to a cell
b. Made of cellulose and other materials
9. Cell membrane
a. Protective barrier that encloses a cell
b. Contains proteins, lipids and 2 layers of
phospholipids
i. Water fearing or hydrophobic
ii. Water loving or hydrophilic
c. Help control the movement of materials
into and out of a cell through specialized
passageways
To recap: the cell membrane 1. Protects the cell
and 2. Helps control the movement of materials into
and out of a cell
Cytoskeleton
Vesicle
10. Cytoskeleton
a. Web of proteins in cytoplasm
b. Acts as a muscle and a skeleton
c. http://www.dnatube.com/video/5968/Cyto
skeleton-microtubules-cell-biology
11. Cell compartments
a. Vesicle = small sac that surrounds
material to be moved into and out of a cell
Lysosomes
Vacuoles
b. Lysosomes = contain digestive enzymes
that do the following…
i. Get rid of wastes
ii. Get rid of old organelles
iii. Protect the cell from foreign invaders
iv. Mostly found in animal cells
c. Vacuoles – a large vesicle
i. Generally found in plant and fungal
cells
ii. Acts like a large lysosome
iii. Some store water and other liquids
Thank you – We are done!!!!! WooHoo!
PLEASE PUT THESE IN A SAFE PLACE
(YOUR SCIENCE FOLDER)!