The observations and conclusions of many scientists
helped to develop the current understanding of the cell
• Robert Hooke (1665)
– English physicist used
primitive compound
microscope to look at
plant tissue (cork).
– He called the chambers
“cells” because they
reminded him of the
small rooms in a
monastery
• Anton van Leeuwenhoek (1674)
– First person to see tiny living
organisms in a drinking water.
(Also observed bacteria in a
human mouth)
– What new information was
learned through
Leeuwenhoek’s observations?
• Matthias Schleiden (1838)
– Concluded that all plants are
made of cells
• Theodore Schwann (1839)
– Concluded that all animals are
made up of cells
• Rudolph Virchow (1855)
– Proposes that all cells come from
existing cells
– What question does this finding
leave unanswered?
All cells share several characteristics that are essential to life.
• Plasma membrane (cell membrane)
– Location: The outer edge that
surrounds the cell and separate it
from its environment.
– Structure: A double layer of
molecules that is flexible
– Function : Regulate the
exchange of materials in and out
of the cell.
• Cytoplasm
– Location: Everything that is inside of the cell membrane
but outside of the nucleus.
– Function: Many important
chemical reactions necessary
for the cell’s survival occur in
the cytoplasm
• Cytoplasm
– Structure: It is made of cytosol and organelles
Cytosol: A gel-like liquid
made of water, dissolved
salts and organic molecules
Organelles: structures
inside the cell that have a
specific function and are
usually membrane bound.
• Ribosomes
– Location: Found throughout the cytoplasm
– Structure: The smallest organelles inside of a cell
– Function: Use
information from DNA
to assemble proteins
» They form peptide
bonds between
individual amino
acids to make
polypeptide chains.
There are two main types of cells; Prokaryotes and
Eukaryotes
Prokaryotic Cells
• Prokaryotic cells are the oldest forms of life and evolved 3.5
billion years ago.
• They are smaller
and less complex
than eukaryotic
cells
• Lack membrane-bound organelles: organelles
enclosed in a membrane inside the cytoplasm
– Their DNA is not
contained inside of a
nuclear membrane
• Prokaryotic organisms:
– are unicellular
– include common
bacteria and bacteria-like
cells (archaea) found in
extreme environments
Eukaryotic Cells
• Eukaryotic cells evolved 2 billion years after prokaryotic
cells
• They are larger and more complex than prokaryotic cells.
• They have membrane bound organelles inside of the
plasma membrane
– Their DNA is contained in a nuclear membrane
• Eukaryotic Organisms:
– Can be unicellular or multicellular
• Unicellular organisms: a single cell carries out of all life’s
functions
• Multicellular organisms: have several specialized cells
that work together to carry out all of life’s functions
– Include plants, animals, protists, and fungi.
Nucleus
Cell Number
DNA
Examples
Cell Size
Prokaryotes
Eukaryotes
No
Yes
Unicellular
Unicellular or
Multicellular
Found in the
Cytoplasm (region
called the nucleoid)
Found in the nucleus
Bacteria
Protist, Fungi, Plants
and Animals
1 – 10 micrometers
10 – 100 micrometers
Nucleus: Contains the cell’s DNA and all instruction for making
protein and other molecules.
The nucleus can be broken down into three smaller structures:
1. Nuclear Envelope
(Nuclear Membrane)
– Found: around the
outside of the nucleus
– Structure: two thin
membranes with
thousands of pores
– Function: allows
materials to move in and
out of the nucleus.
Nucleus: Contains the cell’s DNA and all instruction for making
protein and other molecules.
The nucleus can be broken down into three smaller structures:
1. Nuclear Envelope
(Nuclear Membrane)
– Found: around the
outside of the nucleus
– Structure: two thin
membranes with
thousands of pores
– Function: allows
materials to move in and
out of the nucleus.
2. Nucleolus
– Found: In center of the nucleus
– Structure: a small, dense, round sphere
– Function: Produces the ribosomes.
3. Chromatin
– Found: between the nucleolus
and the nuclear membrane
– Structure: long strands of
DNA wrapped around proteins
– Function: contain genetic
information
• Rough Endoplasmic Reticulum
–
–
–
–
Found
Structure
Function
Related Object
• Smooth Endoplasmic Reticulum
–
–
–
–
Found
Structure
Function
Related Object
• Golgi Apparatus
–
–
–
–
Found
Structure
Function
Related Object
• Lysosomes and Peroxisomes
–
–
–
–
Found
Structure
Function
Related Object
• Vacuoles and Vesicles
–
–
–
–
Found
Structure
Function
Related Object
• Mitochondria
–
–
–
–
Found
Structure
Function
Related Object
• Cytoskeleton
–
–
–
–
Found
Structure
Function
Related Object
• Chloroplast
–
–
–
–
Found
Structure
Function
Related Object
• Cell Wall
–
–
–
–
Found
Structure
Function
Related Object
• Central Vacuole
–
–
–
–
Found
Structure
Function
Related Object
Type of Cell
Plants
Animals
Fungi
Eukaryotic
Eukaryotic
Eukaryotic
Multicellular
Unicellular or
Multicellular
Cell Number
Mulicellular
Vacuoles
Large Central
Vacuole
Small, if present Small, if present
Chloroplast
Present
Absent
Absent
Cell Wall
Present
Absent
Present
Cell
Membrane
Present
Present
Present
Multicellular organism are made of many different types of
cells.
• Specialized Cells: Cells of a multicellular organism that
have a unique structure that has a specific job.
• Structure determines function
Identify the functions of the following cells.
Levels of Organizations in Living Things:
1. Cell: the smallest structure that can be considered living.
2. Tissue: several similar cells working together to perform a
common function.
Examples of Tissues:
Levels of Organizations in Living Things:
3. Organ: a structure that is made of several different types
of tissues performing a specific function.
4. Organ Systems: a system that is made of several different
organs working together to carryout a specific function.