Cells
Levels of cellular organization
 Atom
 Molecule
 Organelle
 Cell
 Tissue
 Organ
 Organ System
 Organism
Cells
Prokaryotic
Bacteria
Eukaryotic
Animal
Plant
Division of Cells
 Eukaryotic Cells
 Literally means “True nucleus”

Have a nucleus
Complex Cells
 Have membrane-bound organelles
 Organisms made of eukaryotic cells are called “eukaryotes”
Examples: Animals, Plants, Fungi, Unicellular organisms like
paramecium and amoeba

Cellular Components
 Cytoplasm

Gel-like substance within the cell where
organelles are found
 Cytoskeleton



“Cell skeleton”
Network of protein fibers that maintain
the shape of cell
Composed of three networks of fibers
1.
2.
3.
Microtubules: largest; hollow tubes
made of protein; determine cell shape;
scaffolding
Intermediate Filaments: Provide
strength of cell
Actin Filaments: smallest; contractile
string-like proteins that allow for cell
movement
Cellular Components
 Cell Membrane
 Semi-permeable barrier that
encloses the cell
 Regulates what enters and exits the
cell
 Provides protection
 Found in all types of cells
 Cell Wall
 Porous, rigid barrier found
surrounding the cell membrane
 Adds additional layer of support and
protection
 Not found in animal cells
Organelles
 Nucleus
 Houses the genetic material
(DNA) needed for replication
of the cell
 “Control Center” of the cell

Contains the instructions for
the creation of proteins
(made from DNA)
Exterior: Surrounded by nuclear envelope: double-layered membrane that
encloses the DNA; contains nuclear pores: small openings that allow for the
passage of molecules between the cytoplasm and the nucleus
Interior: DNA in the form of chromatin (string-like)
• Nucleolus: where ribosomes are made; very dense region
Organelles
 Endoplasmic Reticulum
 A grouping of sac-like
structures
 Two Types of ER:
Rough ER: contain
ribosomes (creating ‘rough’
appearance); involved in the
process of protein synthesis
 Smooth ER: no ribosomes;
involved in lipid synthesis

 Ribosomes
 Location where proteins are
made (protein synthesis)
Organelles
 Golgi Apparatus
 Looks like a stack of membranes (pancake-like appearance)
 Modifies, sorts and packages proteins received from the ER.
Break off from the golgi apparatus; floats freely in the cell or
travels to cell membrane where it will eventually exit the cell.
 Creation of lysosomes

Organelles
 Lysosomes
 Contain enzymes necessary for digestion of cell food or waste
 Can break down lipids, carbs, proteins
 Digest non-functional organelles, ‘cleaning up’ the cell
Organelles
 Vacuoles
 Sac-like structure responsible for storage of various materials
(e.g. water, carbs, proteins, etc.)
Organelles
 Mitochondria
 The “Powerhouse” of the cell
 Convert food energy into energy that is used by the cell itself
(for growth, development, movement, etc.) via cellular
respiration


ATP (Adenosine Triphosphate)
Complex structure
Organelles
 Chloroplast
 Site of photosynthesis


Energy from sun is captured and
converted into chemical energy
Contain the pigment chlorophyll
which absorbs solar energy used in
photosynthesis

Responsible for the green color of
plants
Organelles
 Centrioles
 Made of microtubules
 Located near nucleus
 Organize microtubules within the cytoskeleton prior to cell
division
Division of Cells
 Prokaryotic Cells
 Include Bacteria & Archaea
 Literally means “before nucleus”




So-have no nucleus
Lack membrane-bound organelles
Simpler and much smaller than Eukaryotes
Organisms made of prokaryotic cells are called “prokaryotes”
Structure of Prokaryotes
 Three basic shapes
1.
Bacilli: rod-shaped bacteria
2.
Cocci: Spherical-shaped bacteria
3.
Spirilla: Spiral-shaped bacteria; flexible
Prokaryotic Cell Parts: Interior
Do prokaryotic cells have
DNA if they lack a nucleus?
 Nucleoid: a region within
the cytoplasm of the cell in
which the DNA is located;
center of the cell (no
membrane encloses the
DNA)
 Cytoplasm
 Semifluid, gel-like solution
encased within the cell
membrane of the cell
Interior
 Ribosomes


Made of two subunits
(each containing a
combination of various
proteins and rRNA) which
work together to
synthesize protein
Located throughout the
cytoplasm
External Layers
 Cell Membrane

Regulates the entrance
and exit of various
substances in and out of
the cytoplasm
 Cell Wall

Provides shape, structure,
and support for cell
 Glycocalyx

The outermost layer of
bacterial cells; gel-like
protective layer
External Structures
 Flagella
 Allows for cell movement
 Long, rotating filament that
propels the cell forward
 Fimbriae
 Hair-like bristles located on
the external surface of the
cell
 Allow cells to attach to
surfaces
 Conjugation Pili
 Tube-like structures that
allow for bacteria to pass
DNA from cell to cell; usually
larger and less numerous
than fimbriae