This document is a PowerPoint presentation on cell structure and function. It begins by defining the basic processes of life in cells, including growth, reproduction, responsiveness, and metabolism. It then distinguishes between prokaryotic and eukaryotic cells, noting that prokaryotes lack nuclei and membrane-bound organelles while eukaryotes have these structures. The presentation goes on to describe the various external structures of bacterial cells, including glycocalyces, flagella, fimbriae, and pili. It also explains bacterial cell walls, membranes, and cytoplasmic structures. In addition, it covers similar external features of archaea as well as differences from bacteria.

1. PowerPoint® Lecture
Presentations prepared by
Mindy Miller-Kittrell,
North Carolina State University
C H A P T E R
© 2015 Pearson Education, Inc.
Cell Structure
and Function
3

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Processes of Life
• Growth
• Reproduction
• Responsiveness
• Metabolism

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Figure 3.1 Examples of types of cells.

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Processes of Life
• Tell Me Why
• The smallest free-living microbe—the bacterium
Mycoplasma—is nonmotile. Why is it alive, even though
it cannot move?

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Prokaryotic and Eukaryotic Cells: An Overview
• Prokaryotes
• Include bacteria and archaea
• Have a simple structure
• Lack nucleus
• Lack various membrane-bound internal structures
• Are typically 1.0 µm in diameter or smaller

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Figure 3.2 Typical prokaryotic cell.
Ribosome
Cytoplasm
Nucleoid
Glycocalyx
Cell wall
Cytoplasmic membrane
Flagellum
Inclusions

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Prokaryotic and Eukaryotic Cells: An Overview
• Eukaryotes
• Have nucleus
• Have internal membrane-bound organelles
• Are typically 10–100 µm in diameter
• Have more complex structure
• Include algae, protozoa, fungi, animals, and plants

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Figure 3.3 Typical eukaryotic cell.
Nucleolus
Cilium
Ribosomes
Cytoskeleton
Cytoplasmic
membrane
Smooth endoplasmic
reticulum
Rough endoplasmic
reticulum
Transport vesicles
Golgi body
Secretory vesicle
Centriole
Mitochondrion
Lysosome
Nuclear pore
Nuclear envelope

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Figure 3.4 Approximate size of various types of cells.

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Prokaryotic and Eukaryotic Cells: An Overview
• Tell Me Why
• In 1985, an Israeli scientist discovered a single-celled
microbe, Epulopiscium fishelsoni. This organism is
visible with the naked eye. Why did the scientist think
Epulopiscium was eukaryotic?
• What discovery revealed that the microbe is really a
giant bacterium?

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External Structures of Bacterial Cells
• Glycocalyx
• Gelatinous, sticky substance surrounding the outside of
the cell
• Composed of polysaccharides, polypeptides, or both

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External Structures of Bacterial Cells
• Two Types of Glycocalyces
• Capsule
• Composed of organized repeating units of organic chemicals
• Firmly attached to cell surface
• May prevent bacteria from being recognized by host
• Slime layer
• Loosely attached to cell surface
• Water soluble
• Sticky layer allows prokaryotes to attach to surfaces as biofilms

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Figure 3.5 Glycocalyces.
Glycocalyx
(capsule)
Glycocalyx
(slime layer)

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Motility

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External Structures of Bacterial Cells
• Flagella
• Are responsible for movement
• Have long structures that extend beyond cell surface
• Are not present on all bacteria

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External Structures of Bacterial Cells
• Flagella
• Structure
• Composed of filament, hook, and basal body
• Basal body anchors the filament and hook to cell wall

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Flagella: Structure

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Figure 3.6 Proximal structure of bacterial flagella.
Filament
Rod
Protein rings
Direction
of rotation
during run
Peptidoglycan
layer (cell wall)
Cytoplasmic
membrane
Cytoplasm
Gram + Gram –
Filament
Outer
membrane
Peptidoglycan
layer
Cell
wall
Cytoplasmic
membrane
Cytoplasm
Outer
protein
rings
Rod
Integral
protein
Inner
protein
rings
Integral
protein
Basal
body

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Figure 3.7 Micrographs of basic arrangements of bacterial flagella.

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Flagella: Arrangement

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Spirochetes

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Figure 3.8 Axial filament.
Axial filament
Spirochete
corkscrews
and moves
forward
Axial filament
Cytoplasmic
membrane
Outer
membrane
Axial filament
rotates around
cell
Endoflagella
rotate

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External Structures of Bacterial Cells
• Flagella
• Function
• Rotation propels bacterium through environment
• Rotation reversible; can be counterclockwise or clockwise
• Bacteria move in response to stimuli (taxis)
• Runs
• Tumbles

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Figure 3.9 Motion of a peritrichous bacterium.

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Flagella: Movement

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External Structures of Bacterial Cells
• Fimbriae and Pili
• Fimbriae
• Sticky, bristlelike projections
• Used by bacteria to adhere to one another and to
substances in environment
• Shorter than flagella
• Serve an important function in biofilms

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Flagellum Fimbria
Figure 3.10 Fimbriae.

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External Structures of Prokaryotic Cells
• Pili
• Special type of fimbria
• Also known as conjugation pili
• Longer than fimbriae but shorter than flagella
• Bacteria typically have only one or two per cell
• Transfer DNA from one cell to another (conjugation)

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Figure 3.11 Pili.
Pilus

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External Structures of Prokaryotic Cells
• Tell Me Why
• Why is a pilus a type of fimbria, but a flagellum is not?

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Bacterial Cell Walls
• Provide structure and shape and protect cell from osmotic
forces
• Assist some cells in attaching to other cells or in resisting
antimicrobial drugs
• Can target cell wall of bacteria with antibiotics
• Give bacterial cells characteristic shapes
• Composed of peptidoglycan
• Scientists describe two basic types of bacterial cell walls
• Gram-positive and Gram-negative

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Figure 3.12 Bacterial shapes and arrangements.

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Figure 3.13 Comparison of the structures of glucose, NAG, and NAM.

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Figure 3.14 Possible structure of peptidoglycan.
Sugar
chain
Tetrapeptide
(amino acid)
crossbridge
Connecting chain
of amino acids

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Bacterial Cell Walls
• Gram-Positive Bacterial Cell Walls
• Relatively thick layer of peptidoglycan
• Contain unique polyalcohols called teichoic acids
• Appear purple following Gram staining procedure
• Presence of up to 60% mycolic acid in acid-fast bacteria
helps cells survive desiccation

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Figure 3.15a Comparison of cell walls of Gram-positive and Gram-negative bacteria.
Peptidoglycan layer
(cell wall)
Gram-positive cell wall
Cytoplasmic
membrane
Teichoic acid
Lipoteichoic acid
Integral
protein

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Prokaryotic Cell Walls
• Gram-Negative Bacterial Cell Walls
• Have only a thin layer of peptidoglycan
• Bilayer membrane outside the peptidoglycan contains
phospholipids, proteins, and lipopolysaccharide (LPS)
• Lipid A portion of LPS can cause fever, vasodilation,
inflammation, shock, and blood clotting
• May impede the treatment of disease
• Appear pink following Gram staining procedure

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Figure 3.15b Comparison of cell walls of Gram-positive and Gram-negative bacteria.
Integral
proteins
Outer
membrane
of cell wall
Gram-negative cell wall
Peptidoglycan
layer of cell wall
Cytoplasmic
membrane
Lipopolysaccharide
(LPS) layer, containing
lipid A
Porin
Porin
(sectioned)
Periplasmic space
Phospholipid layers

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Prokaryotic Cell Walls
• Bacteria Without Cell Walls
• A few bacteria lack cell walls
• Often mistaken for viruses because of small size and
lack of cell wall
• Have other features of prokaryotic cells, such as
ribosomes

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Prokaryotic Cell Walls
• Tell Me Why
• Why is the microbe illustrated in Figure 3.2 more likely a
Gram-positive bacterium than a Gram-negative one?

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Bacterial Cytoplasmic Membranes
• Structure
• Referred to as phospholipid bilayer
• Composed of lipids and associated proteins
• Integral proteins
• Peripheral proteins
• Fluid mosaic model describes current understanding of
membrane structure

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Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer.
Phospholipid
Head, which
contains phosphate
(hydrophilic)
Tail
(hydrophobic)
Phospholipid
bilayer
Integral protein
Peripheral protein
Integral
protein
Cytoplasm
Integral
proteins

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Membrane Structure

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Bacterial Cytoplasmic Membranes
• Function
• Control passage of substances into and out of the cell
• Energy storage
• Harvest light energy in photosynthetic bacteria
• Selectively permeable
• Naturally impermeable to most substances
• Proteins allow substances to cross membrane
• Maintain concentration and electrical gradient

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Membrane Permeability

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Cell exterior (extracellular fluid)
Integral
protein
Protein
Cell interior (cytoplasm)
Cytoplasmic membrane
Protein
DNA
mV
Na+
Cl–
–30
Figure 3.17 Electrical potential of a cytoplasmic membrane.

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Passive Transport: Principles of Diffusion

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Bacterial Cytoplasmic Membranes
• Function
• Passive processes
• Diffusion
• Facilitated diffusion
• Osmosis

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Figure 3.18 Passive processes of movement across a cytoplasmic membrane.

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Figure 3.19 Osmosis, the diffusion of water across a semipermeable membrane.

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Figure 3.20 Effects of isotonic, hypertonic, and hypotonic solutions on cells.
Cells without a wall
(e.g., mycoplasmas,
animal cells)
Cells with a wall
(e.g., plants, fungal
and bacterial cells)
H2O
Cell wallCell wall
Cell membrane Cell membrane
Isotonic
solution
Hypertonic
solution
Hypotonic
solution
H2O
H2O
H2OH2OH2O

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Passive Transport: Special Types of Diffusion

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Prokaryotic Cytoplasmic Membranes
• Function
• Active processes
• Active transport
• Group translocation
• Substance is chemically modified during transport

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Figure 3.21 Mechanisms of active transport.
Extracellular fluid
Cytoplasmic
membrane
ATP
ADP
Cytoplasm
Uniport
Antiport Coupled transport:
uniport and symport
Symport
Uniport
ATP
ADP P
P

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Active Transport: Overview

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Active Transport: Types

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Figure 3.22 Group translocation.

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Prokaryotic Cytoplasmic Membranes
• Tell Me Why
• E. coli grown in a hypertonic solution turns on a gene to
synthesize a protein that transports potassium into the
cell. Why?

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Cytoplasm of Bacteria
• Cytosol
• Liquid portion of cytoplasm
• Mostly water
• Contains cell's DNA in region called the nucleoid
• Inclusions
• May include reserve deposits of chemicals

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Figure 3.23 Granules of PHB in the bacterium Azotobacter chroococcum.
Polyhydroxybutyrate

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Cytoplasm of Bacteria
• Endospores
• Unique structures produced by some bacteria
• Defensive strategy against unfavorable conditions
• Vegetative cells transform into endospores when
nutrients are limited
• Resistant to extreme conditions such as heat, radiation,
chemicals

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Figure 3.24 The formation of an endospore.
1
Steps in Endospore Formation
DNA is replicated.
Cytoplasmic membrane
invaginates to form
forespore.
Cytoplasmic membrane
grows and engulfs
forespore within a
second membrane.
Vegetative cell's DNA
disintegrates.
Cell wall
Cytoplasmic
membrane
DNA
Vegetative cell
A cortex of pepti-
doglycan is deposited
between the membranes;
meanwhile, dipicolinic
acid and calcium ions
accumulate within the
center of the endospore.
Spore coat forms
around endospore.
Forespore
First
membrane
Second
membrane
Endospore matures:
Completion of spore coat.
Increase in resistance
to heat and chemicals by
unknown process.
Endospore is released from
original cell.
Cortex
Spore coat
Outer
spore coat
Endospore
2
3
4
8
7
6
5

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Cytoplasm of Prokaryotes
• Nonmembranous Organelles
• Ribosomes
• Sites of protein synthesis
• Composed of polypeptides and ribosomal RNA
• 70S ribosome composed of smaller 30S and 50S subunits
• Many antibacterial drugs act on bacterial ribosomes
without affecting larger eukaryotic ribosomes

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Cytoplasm of Prokaryotes
• Nonmembranous Organelles
• Cytoskeleton
• Composed of three or four types of protein fibers
• Can play different roles in the cell
• Cell division
• Cell shape
• Segregation of DNA molecules
• Movement through the environment

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Figure 3.25 A simple helical cytoskeleton.

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Cytoplasm of Prokaryotes
• Tell Me Why
• The 2001 bioterrorist anthrax attack in the U.S. involved
Bacillus anthracis. Why is B. anthracis able to survive in
mail?

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External Structures of Archaea
• Glycocalyces
• Function in the formation of biofilms
• Adhere cells to one another and inanimate objects
• Flagella
• Consist of basal body, hook, and filament
• Numerous differences from bacterial flagella
• Fimbriae and Hami
• Many archaea have fimbriae
• Some make fimbria-like structures called hami
• Function to attach archaea to surfaces

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Figure 3.26 Archaeal hami.
Grappling
hook
Prickles
Hamus

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External Structures of Archaea
• Tell Me Why
• Why do scientists consider bacterial and archaeal
flagella to be analogous rather than evolutionary
relations?

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Archaeal Cell Walls and Cytoplasmic
Membranes
• Most archaea have cell walls
• Do not have peptidoglycan
• Contain variety of specialized polysaccharides and
proteins
• All archaea have cytoplasmic membranes
• Maintain electrical and chemical gradients
• Control import and export of substances from the cell

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Figure 3.27 Representative shapes of archaea.

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Archaeal Cell Walls and Cytoplasmic
Membranes
• Tell Me Why
• Why did scientists in the 19th and early 20th centuries
think that archaea were bacteria?

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Cytoplasm of Archaea
• Archaeal cytoplasm similar to bacterial cytoplasm
• 70S ribosomes
• Fibrous cytoskeleton
• Circular DNA
• Archaeal cytoplasm also differs from bacterial cytoplasm
• Different ribosomal proteins
• Different metabolic enzymes to make RNA
• Genetic code more similar to that of eukaryotes

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Cytoplasm of Archaea
• Tell Me Why
• Why do some scientists consider archaea, which are
prokaryotic, more closely related to eukaryotes than
they are to bacteria?

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External Structure of Eukaryotic Cells
• Glycocalyces
• Not as organized as prokaryotic capsules
• Help anchor animal cells to each other
• Strengthen cell surface
• Provide protection against dehydration
• Function in cell-to-cell recognition and communication

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External Structure of Eukaryotic Cells
• Tell Me Why
• Why are eukaryotic glycocalyces covalently bound to
cytoplasmic membranes, and why don't eukaryotes with
cell walls have glycocalyces?

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Eukaryotic Cell Walls and Cytoplasmic
Membranes
• Fungi, algae, plants, and some protozoa have cell
walls
• Composed of various polysaccharides
• Cellulose is found in plant cell walls
• Fungal cell walls are composed of cellulose, chitin,
and/or glucomannan
• Algal cell walls are composed of a variety of
polysaccharides

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Figure 3.28 A eukaryotic cell wall.
Cytoplasmic membraneCell wall

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Eukaryotic Cell Walls and Cytoplasmic
Membranes
• All eukaryotic cells have cytoplasmic membrane
• Are a fluid mosaic of phospholipids and proteins
• Contain steroid lipids to help maintain fluidity
• Contain regions of lipids and proteins called
membrane rafts
• Localize signaling, protein sorting, and movement
• Control movement into and out of cell

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Figure 3.29 Eukaryotic cytoplasmic membrane.
Cytoplasmic
membrane
Intercellular
matrix
Cytoplasmic
membrane

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Figure 3.30 Endocytosis.
Pseudopod

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Eukaryotic Cell Walls and Cytoplasmic
Membranes
• Tell Me Why
• Many antimicrobial drugs target bacterial cell walls. Why
aren't there many drugs that act against bacterial
cytoplasmic membranes?

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Cytoplasm of Eukaryotes
• Flagella
• Structure and arrangement
• Differ structurally and functionally from prokaryotic flagella
• Within the cytoplasmic membrane
• Shaft composed of tubulin arranged to form microtubules
• Filaments anchored to cell by basal body; no hook
• May be single or multiple; generally found at one pole of cell
• Function
• Do not rotate but undulate rhythmically

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Figure 3.31a-b Eukaryotic flagella and cilia.
Flagellum
Cilia

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Figure 3.31c Eukaryotic flagella and cilia.
Cytoplasmic
membrane
Cytosol
Central pair
microtubules
"9 + 2"
arrangementMicrotubules
(doublet)
Cytoplasmic membrane
Portion
cut away to show
transition area
from doublets
to triplets and
the end of
central
microtubules
"9 + 0"
arrangement
Microtubules
(triplet)
Basal body

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Cytoplasm of Eukaryotes
• Cilia
• Shorter and more numerous than flagella
• Coordinated beating propels cells through their
environment
• Also used to move substances past the surface of the
cell

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Figure 3.32 Movement of eukaryotic flagella and cilia.

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Cytoplasm of Eukaryotes
• Other Nonmembranous Organelles
• Ribosomes
• Larger than prokaryotic ribosomes (80S versus 70S)
• Composed of 60S and 40S subunits
• Cytoskeleton
• Extensive network of fibers and tubules
• Anchors organelles
• Produces basic shape of the cell
• Made up of tubulin microtubules, actin microfilaments, and
intermediate filaments

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Figure 3.33 Eukaryotic cytoskeleton.
Microtubule
Tubulin
25 nm
Actin
subunit
Microfilament
Intermediate filament
Protein
subunits
7 nm
10 nm

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Cytoplasm of Eukaryotes
• Other Nonmembranous Organelles
• Centrioles and centrosome
• Centrioles are composed of nine triplets of microtubules
• Located in region of cytoplasm called centrosome
• Not found in all eukaryotic cells
• Centrosomes play a role in mitosis, cytokinesis, and
formation of flagella and cilia

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Figure 3.34 Centrosome.
Centrosome (made up of two centrioles)
Microtubules
Triplet

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Nucleus
• Often largest organelle in cell
• Contains most of the cell's DNA
• Semiliquid portion is called nucleoplasm
• Contains chromatin
• RNA synthesized in nucleoli present in nucleoplasm
• Surrounded by nuclear envelope
• Contains nuclear pores

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Figure 3.35 Eukaryotic nucleus.
Nucleolus
Nucleoplasm
Chromatin
Nuclear envelope
Two phospholipid
bilayers
Nuclear pores
Rough ER

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Endoplasmic reticulum
• Netlike arrangement of flattened, hollow tubules
continuous with nuclear envelope
• Functions as transport system
• Two forms
• Smooth endoplasmic reticulum (SER)
• Rough endoplasmic reticulum (RER)

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Figure 3.36 Endoplasmic reticulum.
Free ribosome
Membrane-bound
ribosomes
Mitochondrion
Rough endoplasmic
reticulum (RER)Smooth endoplasmic
reticulum (SER)

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Golgi body
• Receives, processes, and packages large molecules for
export from cell
• Packages molecules in secretory vesicles that fuse with
cytoplasmic membrane
• Composed of flattened hollow sacs surrounded by
phospholipid bilayer
• Not in all eukaryotic cells

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Figure 3.37 Golgi body.
Secretory vesicles
Vesicles
arriving
from ER

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Lysosomes, peroxisomes, vacuoles, and vesicles
• Store and transfer chemicals within cells
• May store nutrients in cell
• Lysosomes contain catabolic enzymes
• Peroxisomes contain enzymes that degrade poisonous
wastes

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Figure 3.38 Vacuole.
Cell wall
Nucleus
Central vacuole
Cytoplasm

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Figure 3.39 The roles of vesicles in endocytosis and exocytosis.
Endocytosis
(phagocytosis)
Smooth
endoplasmic
reticulum
(SER)
Transport
vesicle
Lysosome
Phagolysosome
Golgi body
Secretory
vesicle
Exocytosis
(elimination, secretion)
Phagosome
(food vesicle)
Vesicle
fuses with a
lysosome
Bacterium

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Mitochondria
• Have two membranes composed of phospholipid bilayer
• Produce most of cell's ATP
• Interior matrix contains 70S ribosomes and circular
molecule of DNA

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Figure 3.40 Mitochondrion.
Outer membrane
Inner membrane
Crista
Matrix
Ribosomes

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Cytoplasm of Eukaryotes
• Membranous Organelles
• Chloroplasts
• Light-harvesting structures found in photosynthetic
eukaryotes
• Use light energy to produce ATP
• Have two phospholipid bilayer membranes and DNA
• Have 70S ribosomes

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Granum
Stroma
Thylakoid
Inner bilayer
membrane
Outer bilayer
membrane
Thylakoid
space
Figure 3.41 Chloroplast.

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Cytoplasm of Eukaryotes
• Endosymbiotic Theory
• Eukaryotes formed from union of small aerobic prokaryotes
with larger anaerobic prokaryotes
• Smaller prokaryotes became internal parasites
• Parasites lost ability to exist independently
• Larger cell became dependent on parasites for
metabolism
• Aerobic prokaryotes evolved into mitochondria
• Similar scenario for origin of chloroplasts
• Theory is not universally accepted

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Cytoplasm of Eukaryotes
• Tell Me Why
• Colchicine is a drug that inhibits microtubule formation.
Why does colchicine inhibit phagocytosis, movement of
organelles within the cell, and formation of flagella and
cilia?

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Important topics
• Difference among cilia, flagella, pili, fimberia, pseudopodia.
• Structure and function of peptidoglycan, lipid A, mycolic acid.
• Differences between gram positive and gram negative bacteria.
• Endo vs. exotoxin
• Special bacteria such as mycoplasma and mycobacterium
• Structure and function of chloroplast, mitochondria, peroxysome,
lysosome
• Definition of epidemiology, biotechnology, molecular biology,
nosocomial infection
• Transportation across the cell membrane and cell wall, such as simple
diffusion, facilitated diffusion, endocytosis, exocytosis