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Advanced Biology
Cell Structure
Chapter 5
All organisms are
composed of cells
 Prokaryotes have a single circular
molecule of DNA, while eukaryotic
cells have a nucleus, bounded by a
nuclear membrane and containing
DNA.
All organisms are
composed of cells
 Cytoplasm fills the interior of the cell,
exclusive of the nucleus, and a plasma
membrane encloses the cell and
separates it from its surroundings. The
plasma membrane contains several
types of proteins that allow the cell to
interact with its environment.
All organisms are
composed of cells
 Early cell theory included three
principles: (1) All organisms are
composed of one or more cells; (2)
cells are the smallest living things;
and (3) cells arise only by division of
previously existing cells.
All organisms are
composed of cells
 Smaller cells are more advantageous
than larger cells due to the limitations
of communication in relation to surface
area-to-volume ratios.
Eukaryotic cells are more
structurally complex than
prokaryotic cells.
 Most prokaryotic cells are encased by
a strong cell wall and can be classified
using the Gram staining procedure.
 Gram Positive – thicker cell wall
retains the violet stain
 Gram Negative – thinner wall, does
not retain violet stain, but will appear
pink due to the second stain applied.
Eukaryotic cells are more
structurally complex than
prokaryotic cells.
 Some prokaryotes use a flagellum for
locomotion.
 Because prokaryotic cells lack
membrane-bounded organelles, all
cytoplasmic constituents have access
to all areas of the cell.
Eukaryotes: Cells with Complex
Interiors
 Eukaryotic cells have extensive
internal compartmentalization, with
multiple membrane-bounded
organelles carrying out specific
functions.
The Nucleus: Information Center for
the Cell
 The nucleus is the repository for the
genetic information that directs cell
activities.
 The surface of the nucleus is bounded
by two phospholipid bilayer
membranes that form the nuclear
envelope.
The Nucleus: Information Center for
the Cell
 DNA is organized into chromosomes
located in the nucleus.
The Endomembrane System
 The endoplasmic reticulum is an
extensive system of folded
membranes that compartmentalizes
the cell's interior.
 The Golgi apparatus collects,
packages, modifies, and distributes
molecules throughout the cell.
The Endomembrane System
 Lysosomes contain digestive enzymes
that catalyze the rapid breakdown of
proteins, nucleic acids, and
carbohydrates.
Ribosomes: Sites of Protein
Synthesis
 Two ribosomal subunits join to form a
ribosome when they attach to
messenger RNA to direct protein
synthesis.
The Cytoskeleton: Interior
Framework of the Cell
 The cytoplasm of all eukaryotic cells is
meshed by a network of protein fibers
called the cytoskeleton, which
supports the shape of the cell and
anchors its organelles.
The Cytoskeleton: Interior
Framework of the Cell
 Eukaryotic cells may contain three
types of cytoskeletal fibers: actin
filaments, microtubules, and
intermediate filaments.
Not all eukaryotic cells are the
same.
 Vacuoles and Cell Walls
Plant cells usually contain a large
central vacuole for storage, and are
encased by thick cell walls and often
even by strong secondary walls.
Not all eukaryotic cells are the
same.
 The Extracellular Matrix
Animal cells lack the thick cell walls of
plants, but secrete a mixture of
glycoproteins to form an extracellular
matrix, which helps coordinate the
behavior of all the cells in a particular
tissue.