PowerPoint® Lecture
Presentations prepared by
Mindy Miller-Kittrell,
North Carolina
State University
CHAPTER
3
Cell Structure
and Function
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Processes of Life
• Growth
• Reproduction
• Responsiveness
• Metabolism
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Prokaryotic and Eukaryotic Cells: An Overview
• Prokaryotes
• Composed of bacteria and archaea
• Lack nucleus
• Lack various internal structures bound with phospholipid
membranes
• Are typically 1.0 µm in diameter or smaller
• Have a simple structure
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Figure 3.2 Typical prokaryotic cell.
Inclusions
Ribosome
Cytoplasm
Nucleoid
Glycocalyx
Flagellum
Cell wall
Cytoplasmic membrane
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Prokaryotic and Eukaryotic Cells: An Overview
• Eukaryotes
• Have nucleus
• Have internal membrane-bound organelles
• Are larger: 10–100 µm in diameter
• Have more complex structure
• Composed of algae, protozoa, fungi, animals, and
plants
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Figure 3.3 Typical eukaryotic cell.
Nuclear envelope
Nuclear pore
Nucleolus
Lysosome
Mitochondrion
Centriole
Secretory vesicle
Golgi body
Cilium
Transport vesicles
Ribosomes
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Cytoplasmic
membrane
Cytoskeleton
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External Structures of Bacterial Cells
• Glycocalyces
• 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
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Figure 3.5 Glycocalyces.
Glycocalyx
(capsule)
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Glycocalyx
(slime layer)
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
PLAY
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Flagella: Structure
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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External Structures of Prokaryotic Cells
• Pili
• Special type of fimbria
• Also known as conjugation pili
• Longer than fimbriae but shorter than flagella
• Bacteria typically only have one or two per cell
• Transfer DNA from one cell to another (conjugation)
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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 3.13 Possible structure of peptidoglycan.
Sugar
backbone
Tetrapeptide
(amino acid)
crossbridge
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Connecting chain
of amino acids
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
• Up to 60% mycolic acid in acid-fast bacteria helps cells
survive desiccation
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Figure 3.14a Comparison of cell walls of Gram-positive and Gram-negative bacteria.
Peptidoglycan layer
(cell wall)
Cytoplasmic
membrane
Gram-positive cell wall
Lipoteichoic acid
Teichoic 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, inflammation,
shock, and blood clotting
• Appear pink following Gram staining procedure
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Figure 3.14b Comparison of cell walls of Gram-positive and Gram-negative bacteria.
Porin
Outer
membrane
of cell wall
Porin
(sectioned)
Peptidoglycan
layer of cell wall
Gram-negative cell wall
Periplasmic space
Cytoplasmic
membrane
Phospholipid layers
Lipopolysaccharide
(LPS) layer, containing
lipid A
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Integral
proteins
Prokaryotic Cell Walls
• Bacteria Without Cell Walls
• A few bacteria lack cell walls
• Often mistaken for viruses due to small size and lack of
cell wall
• Have other features of prokaryotic cells such as
ribosomes
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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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Bacterial Cytoplasmic Membranes
• Function
• Energy storage
• Harvest light energy in photosynthetic bacteria
• Naturally impermeable to most substances
• Proteins allow substances to cross membrane
• Maintain concentration and electrical gradient
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Passive Transport: Principles of Diffusion
PLAY
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Passive Transport: Principles of Diffusion
Bacterial Cytoplasmic Membranes
• Function
• Passive processes
• Diffusion
• Facilitated diffusion
• Osmosis
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Figure 3.17 Passive processes of movement across a cytoplasmic membrane.
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Figure 3.19 Effects of isotonic, hypertonic, and hypotonic solutions on cells.
Cells without a wall
(e.g., mycoplasmas,
animal cells)
H2O
Cell wall
Cells with a wall
(e.g., plants, fungal
and bacterial cells)
Cell wall
Isotonic
solution
H2O
H2O
H2O
Cell membrane
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H2O
H2O
Cell membrane
Hypertonic
solution
Hypotonic
solution
Passive Transport: Special Types of Diffusion
PLAY
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Passive Transport: Special Types of Diffusion
Prokaryotic Cytoplasmic Membranes
• Function
• Active processes
• Active transport
• Group translocation
• Substance is chemically modified during transport
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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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Cytoplasm of Bacteria
• Endospores
• Unique structures produced by some bacteria
• Vegetative cells transform into endospores when
multiple nutrients are limited
• Resistant to extreme conditions such as heat, radiation,
chemicals
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Figure 3.23 The formation of an endospore.
Steps in Endospore Formation
Cell wall
Cytoplasmic
membrane
1 DNA is replicated.
DNA
Vegetative cell
2 DNA aligns along
the cell’s long axis.
3 Cytoplasmic membrane
invaginates to form
forespore.
4 Cytoplasmic membrane
grows and engulfs
forespore within a
second membrane.
Vegetative cell’s DNA
disintegrates.
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Forespore
First
membrane
Second
membrane
5 A cortex of peptidoglycan
is deposited between the
membranes; meanwhile,
dipicolinic acid and
calcium ions accumulate
within the center of the
endospore.
Cortex
6 Spore coat forms
around endospore.
Spore coat
7 Endospore matures:
completion of spore coat
and increase in resistance
to heat and chemicals by
unknown process.
Outer
spore coat
8 Endospore is released from
original cell.
Endospore
Cytoplasm of Prokaryotes
• Nonmembranous Organelles
• Ribosomes
• Sites of protein synthesis
• Composed of polypeptides and ribosomal RNA
• Cytoskeleton
• Composed of three or four types of protein fibers
• Can play different roles in the cell
• Cell division
• Cell shape
• Segregate DNA molecules
• Move through the environment
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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 3.26 Representative shapes of archaea.
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Eukaryotic Cell Walls and Cytoplasmic
Membranes
• Fungi, algae, plants, and some protozoa have cell walls
• Composed of various polysaccharides
• Cellulose found in plant cell walls
• Fungal cell walls composed of cellulose, chitin, and/or
glucomannan
• Algal cell walls composed of a variety of polysaccharides
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Figure 3.27 A eukaryotic cell wall.
Cell wall
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Cytoplasmic membrane
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
• Control movement into and out of cell
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Figure 3.28 Eukaryotic cytoplasmic membrane.
Cytoplasmic
membrane
Intercellular
matrix
Cytoplasmic
membrane
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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 3.30a-b Eukaryotic flagella and cilia.
Flagellum
Cilia
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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 3.31 Movement of eukaryotic flagella and cilia.
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Cytoplasm of Eukaryotes
• Membranous Organelles
• Nucleus
• Often largest organelle in cell
• Contains most of the cell's DNA
• Semiliquid portion called nucleoplasm
• Contains chromatin
• RNA synthesized in nucleoli present in nucleoplasm
• Surrounded by nuclear envelope
• Contains nuclear pores
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Figure 3.34 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 3.35 Endoplasmic reticulum.
Membrane-bound
ribosomes
Mitochondrion
Free ribosome
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Smooth endoplasmic
reticulum (SER)
Rough endoplasmic
reticulum (RER)
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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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 3.37 Vacuole.
Cell wall
Nucleus
Central vacuole
Cytoplasm
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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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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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Figure 3.40 Chloroplast.
Granum
Stroma
Thylakoid
space
Thylakoid
Inner bilayer
membrane
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Outer bilayer
membrane
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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 aerobic ATP
production
• Aerobic prokaryotes evolved into mitochondria
• Similar scenario for origin of chloroplasts
• Theory is not universally accepted
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© 2014 Pearson Education, Inc.