1. The Cytoskeleton Microfilaments
• A networked mesh of protein rods that • Thin (but dense),
support the cell, acting as scaffolding cross-linked strands
• Also contain contractile units that allow for the of actin (contractile
movement of cells and for intracellular proteins)
movement (organelle movement, vesicular • Involved in cell
transport) motility and changes
• Three Types: in shape
– Microtubules
– Microfilaments
– Intermediate filaments
1 2
Intermediate Filaments Microtubules
• Tough, stable, • Long, hollow tubes
permanent, rope-like composed of tubulin.
protein fibers Large in diameter
• Have high tensile • Radiate from the
strength centrosome
• Helps cells resist • Determine cell shape
mechanical stress and organelle
and are found in distribution
desmosomes for cell- • Important in
cell contact 3 intracellular transport
4
Centrosome & Centrioles Cellular Extensions: Cilia
• “microtubule organizing
center”
• Composed of two
centrioles (90o to each
other) and a granular
matrix
• Matrix generates
microtubules
• Centrioles generate
spindle fibers during cell
5 6
division
1

2. Cellular Extensions: Flagella Cellular Extensions: Microvilli
• Sperm cells are the
only cells in the
human body with
flagella
• Similar to cilia but are
longer and allow cells
to propel themselves • Finger-like plasma membrane projections
• Use a whip-like • Increases plasma membrane surface area
motion for locomotion • Typically found in absorptive cells
7 • Example: Lining of the small intestine 8
The Nucleus The Nuclear Envelope
• The “control center” of • Double membrane barrier
the cell containing separated by a fluid-filled space
genetic information • Outer membrane is continuous
with RER & is studded with
• The largest organelle of ribosomes
the cell and is filled with
• Inner membrane is lined with
nucleoplasm
nuclear lamina
• Two membranes come together
• Composed of: Nuclear
and form nuclear pores (entry and
envelope, Nucleolus,
exit point of particles)
and Chromatin 9 10
Nucleoli Chromatin
• Loosely coiled DNA fibers
• Small, dense body and histone proteins,
composed of RNA and condense to form
protein, where chromosomes.
ribosomes are • DNA + histone =
synthesized nucleosome
• Condense into
chromosomes during cell
11
division 12
2

3. The Cell Cycle Interphase
• Cell growth and DNA
• Cell cycles form a multi- replication, “preparation
celled organism from one period”
original cell
• A series of changes cells go • G1 Phase: Growth Phase
through from the time they 1, structures are
are formed until they divide duplicated
• Promote growth and tissue • S Phase: Synthesis
repair in organisms Phase, DNA is replicated
• Involves phases and • G2 Phase: Growth Phase
checkpoints for quality 2, more structural
control duplication, final
13
*Movie time! preparations 14
DNA Replication
Mitosis
• Division of the nucleus:
– Prophase
– Metaphase
– Anaphase
– Telophase
• Cytokinesis: Division of the cytoplasm
• Occurs before cell division • Exceptions: RBCs, nervous, skeletal &
• DNA is uncoiled & H-bonds broken by a helicase cardiac tissue
• DNA polymerase introduces complementary bases
• Replicated DNA is semi-conservative 15 16
• DNA condenses after replication
Mitosis Mitosis
17 18
3

4. Protein Synthesis Transcription
• Synthesis of
• DNA provides the
complementary
information for
mRNA (messenger
protein synthesis
RNA)
• Transcribes the
• Two events: code for making
– Transcription proteins and
– Translation transports it outside
the nucleus
19 20
Translation Translation
• Every mRNA codon
corresponds to an
amino acid
• Examples:
– CAC = Histidine
– CAA = Glutamine
– AAA = Lysine
21 22
23 24
4