3.1 The Cellular Level of
Organization
• All life is “cellular”
• Unicellular organisms like Archaea,
Bacteria, protists
• Multicellular eukaryotes like fungi, plants,
and animals
• Exceptions: Viruses are ‘acellular’ but
exhibit life qualities when acting as a
parasite within host cells
3.1 The Cellular Level of
Organization
• The cell is the structural and functional unit
of an organism, the smallest structure
capable of performing all the functions
necessary for life.
3.1 The Cellular Level of
Organization
• Prokaryotic cells lack membrane enclosed
structures. No nucleus or “organelle”
compartments
• Eukaryotic cells possess membrane
enclosed structures. Prominent nucleus
and distinct compartments - organelles
The Cell Theory
• All organisms are composed of
one or more cells.
• Robert Hooke, Louis Pasteur,
Leuwenhoek, Virchow and others
helped form the “cell theory”
The Cell Theory
• All organisms are composed of one or
more cells.
• Cells are the basic living unit of
structure and function in
organisms.
The Cell Theory
• All organisms are composed of one or
more cells.
• Cells are the basic living unit of structure
and function in organisms.
• All cells come only from other
cells.
Sizes of Living Things
Surface Area / Volume Ratio
• The amount of surface area affects the
ability to get materials in and out of a cell.
• Cells are “small”. Their size is limited.
Size is limited by S/V ratio.
Surface Area / Volume Ratio
• The amount of surface area affects the
ability to get materials in and out of a cell.
• A cells increase in volume, the
proportionate amount of surface area
decreases.
Surface Area / Volume Ratio
Plasma Membrane and
Cytoplasm
• All cells are surrounded
by a plasma membrane
(AKA cytoplasmic memb.,
cell memb.).
• The material inside of a
cell is the cytoplasm.
• The plasma membrane
regulates what enters and
exits a cell.
3.2 Prokaryotic Cells
• Smaller in size than Eukaryotes (1 – 10
microns)
• Unicellular, no nucleus or organelles
• Archaea
• Bacteria
3.2 Prokaryotic Cells
3.2 Prokaryotic Cells
• Cell Wall - Unique
Polysaccharide,
Peptidoglycan
• Capsule- Sugar coat
• Flagellum - Motor
• Nucleoid - DNA
• Ribosomes
3.2 Prokaryotic Cells
• Cell Wall
• Capsule
• Flagellum
• Nucleoid
• Ribosomes
Prokaryotes are:
• Structurally simple
• Metabolically diverse
• Adapted to most
types of environments
3.2 Prokaryotic Cells
3.3 Eukaryotic Cells
• Larger in size than Prokaryotes (10 to 50
microns)
• Membrane bound organelles
(compartments with specialized functions)
3.3 Eukaryotic Cells
• Eukaryotic cells:
– Are structurally complex
– Have a nucleus
– Possess membrane-bound organelles
– May have a cell wall
3.3 Eukaryotic Cells
3.3 Eukaryotic Cells – Review
these for assessment test,
particularly the animal cell
The Nucleus
• Stores DNA
The Nucleus
• Stores DNA
• Nucleolus - rRNA
The Nucleus
• Stores DNA
• Nucleolus - rRNA
• Nuclear Envelope
– Nuclear pores
Ribosomes
• Site of protein synthesis
• Two subunits (large and small)
– Subunits consist of rRNA and protein molecules
• Polyribosomes
– Several ribosomes with a single mRNA molecule
Endoplasmic Reticulum
• Consists of
membranous
channels and
saccules
Endoplasmic Reticulum
• Rough ER
– Processing and
modification of
proteins
• Smooth ER
– Synthesizes
phospholipids
– Various other functions
Golgi Apparatus
• The Golgi apparatus
collects, sorts,
packages, and
distributes materials
such as proteins and
lipids.
Lysosomes
• Lysosomes contain
digestive enzymes
that break down
unwanted, foreign
substances or wornout parts of cells
Vacuoles
• Vacuoles are
membranous sacs
that store substances.
– For example:
Water
Pigments
Toxins
Peroxisomes
• Membrane bound vesicles containing enzymes.
– The enzymes break down molecules and as a result
produce hydrogen peroxide.
– Toxic oxygen waste products – free radicals, can
cause serious problems
– Detoxification by special enzymes like SOD to less
toxic hydrogen peroxide
– Hydrogen peroxide is broken down to water and
oxygen by the enzyme catalase
Energy-Related Organelles
• Chloroplasts
• Mitochondria
Energy-Related Organelles
Photosynthesis
Cellular Respiration
Chloroplasts
• Site of photosynthesis
• Structure:
– Double-membrane
– Stroma
– Grana
• Thylakoids
• Chloroplasts contain:
– Their own DNA
– Ribosomes
– Enzymes
Mitochondria
• Found in all eukaryotic
cells
• Site or cellular respiration
• Structure:
– Double-membrane
– Matrix
– Crista
The Cytoskeleton
• Maintains cell shape
• Assists in movement of cell and organelles
• Assemble and disassemble as needed
• Three types of macromolecular fibers
– Actin Filaments
– Intermediate Filaments
– Microtubules
Actin Filaments
•
•
•
•
Anchored to the plasma membrane
Allows intestinal microvilli to expand and contract
Found in pseudopods allowing amoeboid movement
Play a role in animal cell division
Actin Filaments
• Actin interacts with motor molecules such as myosin.
• In the presence of ATP, myosin pulls actin along
• Example: muscle cells
Intermediate Filaments
• Intermediate in size between actin filaments and
microtubules
• Functions:
– Support nuclear envelope
– Cell-cell junctions, such as those holding skin cells tightly
together
Microtubules
• Hollow cylinders made of two globular proteins
• Assembly:
– Under control of Microtubule Organizing Center
(MTOC)
– Most important MTOC is centrosome
• Interacts with specific proteins to cause movement of
organelles
Microtubule Operation
Centrioles
• Short cylinders with a 9 + 0 pattern of
microtubule triplets
Centrioles
• Help organize microtubules during animal cell division
• May be involved with microtubule formation and in the
organization of cilia and flagella
Cilia and Flagella
• Hairlike projections that aid in cell movement
• In eukaryotic cells, cilia are much shorter than flagella
• They are membrane-bound cylinders enclosing a matrix
area
– The matrix consists of microtubules in a 9 + 2 pattern
Cilia and Flagella