Eukaryotic cells have internal membranes that compartmentalize their functions. Prokaryotic cells lack membrane-bound organelles and have DNA in the nucleoid, while eukaryotic cells have a nucleus bounded by a nuclear envelope that contains DNA, as well as other membrane-bound organelles. The endomembrane system, including the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles and plasma membrane, works together to transport materials within the cell.

1. Chapter 6
A Tour of the Cell
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

2. Eukaryotic cells have internal membranes that
compartmentalize their functions
• Basic features of all cells: plasma membrane, cytosol, chromosomes,
ribosomes
• Prokaryotic vs Eukaryotic cells
– prokaryotic cells  Bacteria and Archaea
• No nucleus
• DNA in an unbound region called the nucleoid
• No membrane-bound organelles
• Cytoplasm bound by the plasma membrane
– eukaryotic cells  Protists, fungi, animals and plants
• DNA in a nucleus bounded by nuclear envelope
• Membrane-bound organelles
• Cytoplasm in the region between the plasma membrane and
nucleus
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3. Fig. 6-6
Prokaryotic cell
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial Cell wall
chromosome
Capsule
0.5 µm
Flagella

4. Fig. 6-9a
Eukaryotic Animal Cell
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Nucleolus NUCLEUS
Rough ER Smooth ER
Flagellum*** Chromatin
(not in plants)
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules Ribosomes
Microvilli
Golgi
Peroxisome apparatus
Mitochondrion
Lysosome***
(not in plants/prokaryotes)

5. Fig. 6-9b
Eukaryotic Plant Cell
Nuclear envelope Rough endoplasmic reticulum
NUCLEUS Nucleolus
Chromatin
Smooth endoplasmic reticulum
Ribosomes
Central
Golgi vacuole***
apparatus
Microfilaments
Intermediate CYTO-SKELETON
filaments
Microtubules
Mitochondrion
Peroxisome
Chloroplast***
Plasma
membrane
Cell
wall***
Plasmodesmata***
Wall of adjacent cell
***specific to plants

6. Organelles to know
• Nucleus – Genetic information
• Ribosomes – protein factories
• Endoplasmic Reticulum – protein trafficking and metabolic functions
• Golgi Apparatus – shipping and receiving center
• Lysosomes – digestive compartments
• Vacuoles – maintenance compatments
• Mitochondria – chemical energy conversion (site of cellular respiration)
• Chloroplasts – light energy conversion (site of photosynthesis)
• Peroxisomes - oxidation
• Cytoskeleton – support, motility and regulation
• Extracellular Matrix – support, adhesion, movement, regulation
• Intercellular Junctions – facilitate contact between cells

7. Nucleus: Information Central
– nuclear envelope encloses the nucleus, separating it from the
cytoplasm
– nuclear membrane is a double membrane; each membrane
consists of a lipid bilayer
– Pores regulate the entry and exit of molecules from the nucleus
– The shape of the nucleus is maintained by the nuclear lamina,
which is composed of protein
– In the nucleus, DNA and proteins form genetic material called
chromatin
– Chromatin condenses to form discrete chromosomes
– The nucleolus is located within the nucleus and is the site of
ribosomal RNA (rRNA) synthesis
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8. Fig. 6-10
Nucleus
1 µm Nucleolus
Chromatin
Nuclear envelope
Nuclear pore
Pore
complex
Surface of
nuclear envelope
Ribosome 1 µm
0.25 µm
Close-up of nuclear
envelope
Pore complexes Nuclear lamina

9. Ribosomes: Protein factories
– particles made of ribosomal RNA and protein
– Protein synthesis occurs here
• Free ribosomes are localized to the cytosol
• Bound ribosomes are on the ER or the nuclear envelope
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large subunit
Fig. 6-11 Small subunit
Diagram of a ribosome

10. Endoplasmic Reticulum (ER): Protein Trafficking
– The ER membrane is attached to the nuclear envelope
– There are two distinct regions of ER:
• Smooth ER  lacks ribosomes
– Synthesizes lipids
– Metabolizes carbohydrates
– Detoxifies poison
– Stores calcium
• Rough ER with ribosomes
– Secretes glycoproteins (proteins covalently bonded to
carbohydrates)
– Distributes transport vesicles, proteins surrounded by
membranes
– membrane factory for the cell
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11. Fig. 6-12
Smooth ER
Rough ER Nuclear
envelope
Ribosomes
Transport vesicle
Rough ER
Smooth ER

12. Golgi apparatus: Shipping and Receiving Center
– shipping and receiving center
– consists of flattened membranous sacs called cisternae
– Functions:
• Modifies products of the ER
• Manufactures certain macromolecules
• Sorts and packages materials into transport vesicles
Cisternae
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13. Lysosome: Digestive Compartment
– a membranous sac of hydrolytic enzymes that can digest macromolecules
– Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and
nucleic acids
• After phagocytosis (engulfing of another cell) lysosomes fuse with the
food vacuole and digests the molecules
• Autophagy uses enzymes to recycle the cell’s own organelles and
macromolecules
(a) Phagocytosis (b) Autophagy
Digestive
enzymes
Lysosome Lysosome
Plasma Peroxisome
membrane
Digestion
Food vacuole Digestion
Mitochondrion
Vesicle
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14. Fig. 6-15
Vacuoles: Maintenance Compartment
– Diverse
Maintenance
Compartments
Central
– Food vacuole
vacuoles are Cytosol
formed by
phagocytosis
– Contractile
vacuoles Nucleus Central
vacuole
pump excess
water out of Cell wall
cells Chloroplast
– Central
vacuoles (in
many mature
plant cells)
hold organic
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15. The Endomembrane System: A Review
• The endomembrane system is a complex and dynamic
player in the cell’s compartmental organization
– Nuclear envelope
– ER
– Golgi apparatus
– Lysosomes
– Vacuoles
– Plasma membrane
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16. Fig. 6-16-3
Nucleus
Rough ER
Smooth Golgi
ER Transport vessicle
Transport vessicle
Lysosome Plasma
membrane
•Nuclear envelope is connected to rough ER
•Proteins produced by the ER flow in transport vessicles to the Golgi
•Golgi pinches off vessicles that give rise to lysosomes, vessicles and vacuoles
•Lysosomes can fuse with another vessicle for digestion
•Transport vessicle carries proteins to plasma membrane for secretion
•Plasma membrane expands by fusion of vessicles; proteins are secreted from the cell

17. Mitochondria: Chemical Energy Conversion
– sites of cellular respiration, a metabolic process that generates ATP
– Have a double membrane
– Contain their own DNA
– Mitochondria are in nearly all eukaryotic cells
– They have a smooth outer membrane and an inner membrane folded
into cristae
• Cristae present a large surface area for enzymes that
synthesize ATP
– The inner membrane creates two compartments: intermembrane
space and mitochondrial matrix
• Some metabolic steps of cellular respiration are catalyzed in the
mitochondrial matrix
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18. Fig. 6-17
Intermembrane space
Outer
membrane
Free ribosomes
in the
mitochondrial
matrix
Inner
membrane
Cristae
Matrix
0.1 µm

19. Chloroplasts: Light Energy Conversion
– Capture light energy, are the sites of photosynthesis
– found in plants and algae
– Have a double membrane (similar to mitochondria)
– Contain their own DNA (similar to mitochondria)
– contain chlorophyll and other molecules that function in photosynthesis
– found in leaves and other green organs of plants and in algae
Ribosomes
Stroma
Inner and outer
membranes
Granum
1 µm
Thylakoid
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20. Peroxisome: Oxidation
– oxidative organelles
Chloroplast
Peroxisome
– specialized
Mitochondrion
metabolic
compartments
bounded by a single
membrane
– produce hydrogen
peroxide and convert
it to water
1 µm
– Oxygen is used to
break down different
types of molecules
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21. Cytoskeleton: Support, Motility and Regulation
– a network of fibers extending throughout the cytoplasm
– organizes the cell’s structures and activities, anchoring many
organelles
– composed of three types of molecular structures:
• Microtubules are the thickest of the three components
• Microfilaments, also called actin filaments, are the thinnest
components
• Intermediate filaments are fibers with diameters in a middle
range
– helps to support the cell and maintain its shape
– interacts with motor proteins to produce motility
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22. Microtubules
• Functions
– Shaping the cell
– Guiding movement of organelles
– Separating chromosomes during cell division
• Centrosomes
– The centrosome is a “microtubule-organizing center”
– microtubules grow out from a centrosome near the nucleus and
attach to chromosomes during mitosis
• Cilia and Flagella
– Microtubules control the beating of cilia and flagella
– A core of microtubules sheathed by the plasma membrane
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23. Microtubules separate chromosomes during mitosis
Centrosome
microtubules
Microtubule
centrosome
Fig. 6-22

24. Microtubules assist in motility
(a) EX: Motion of flagella in sperm (b) EX: Motion of cilia in aquatic life
Fig. 6-23

25. Fig. 6-24
Microtubule structure in cilia
Plasma
membrane
Microtubules
(b) Cross section of
Plasma cilium
membrane
Basal body
(a) Longitudinal
section of cilium
(c) Cross section of basal body

26. Microfilaments (Actin Filaments)
• Microfilaments are solid rods Microvillus
built as a twisted double chain of
actin subunits
• The structural role: bear tension
and resist pulling forces within the
cell Microfilaments
• (actin filaments)
Cellular function: cellular motility
– Myosin and actin contribute to
this
• Examples
– Muscle contraction Intermediate
filaments
– Ameoboid movement occurs
through Pseudopodia
– Cytoplasmic streaming
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27. Intermediate Filaments
• They support cell shape and fix organelles in place
• more permanent cytoskeleton fixtures than the other two classes
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28. Cell Walls of Plants
• Prokaryotes, fungi, and some protists also have cell walls
• Functions: protects the plant cell, maintains its shape, prevents
excessive uptake of water
• made of cellulose fibers
• Plant cell walls may have multiple layers:
– Primary cell wall: relatively thin and flexible
– Middle lamella: thin layer between primary walls of
adjacent cells
– Secondary cell wall (in some cells): added between the
plasma membrane and the primary cell wall
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29. Fig. 6-28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata

30. The Extracellular Matrix (ECM) of Animal Cells
• Functions
– Support
– Adhesion Proteoglycan
Collagen
EXTRACELLULAR MATRIX complex
– Movement
– Regulation
• made up of Fibronectin
glycoproteins
(collagen,
proteoglycans, and
fibronectin) Integrins
• ECM proteins bind
to receptor proteins
in the plasma
Micro- CYTOPLASM
membrane called filaments
integrins
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31. Intercellular Junctions
• Neighboring cells in tissues, organs, or organ systems often adhere,
interact, and communicate through direct physical contact
• Intercellular junctions facilitate this contact
• There are several types of intercellular junctions
– Plasmodesmata – channels that perforate cell walls
– Tight junctions - membranes of neighboring cells are pressed
together, preventing leakage of extracellular fluid
– Desmosomes (anchoring junctions) fasten cells together into
strong sheets
– Gap junctions (communicating junctions) provide cytoplasmic
channels between adjacent cells
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32. Fig. 6-32
Tight Tight junctions prevent
junction fluid from moving
across a layer of cells
0.5 µm
Tight junction Desmosomes fasten
cells together in sheets
Intermediate
filaments
Desmosome
Gap Desmosome
junctions
Gap junctions all cells to
communicate with one
Space
Extracellular another via cytoplasmic
matrix
between Gap channels
cells junction
Plasma membranes
of adjacent cells
0.1 µm

33. Fig. 6-UN1
Cell Component Structure Function
Concept 6.3 Nucleus Surrounded by nuclear Houses chromosomes, made of
The eukaryotic cell’s genetic envelope (double membrane) chromatin (DNA, the genetic
instructions are housed in perforated by nuclear pores. material, and proteins); contains
the nucleus and carried out The nuclear envelope is nucleoli, where ribosomal
by the ribosomes continuous with the subunits are made. Pores
endoplasmic reticulum (ER). regulate entry and exit of
materials.
(ER)
Ribosome Two subunits made of ribo- Protein synthesis
somal RNA and proteins; can be
free in cytosol or bound to ER
Concept 6.4 Endoplasmic reticulum Extensive network of Smooth ER: synthesis of
The endomembrane system membrane-bound tubules and lipids, metabolism of carbohy-
regulates protein traffic and (Nuclear sacs; membrane separates drates, Ca2+ storage, detoxifica-
performs metabolic functions envelope) lumen from cytosol; tion of drugs and poisons
in the cell continuous with
the nuclear envelope. Rough ER: Aids in synthesis of
secretory and other proteins from
bound ribosomes; adds
carbohydrates to glycoproteins;
produces new membrane
Golgi apparatus Stacks of flattened Modification of proteins, carbo-
membranous hydrates on proteins, and phos-
sacs; has polarity pholipids; synthesis of many
(cis and trans polysaccharides; sorting of Golgi
faces) products, which are then
released in vesicles.
Lysosome Membranous sac of hydrolytic Breakdown of ingested substances,
enzymes (in animal cells) cell macromolecules, and damaged
organelles for recycling
Vacuole Large membrane-bounded Digestion, storage, waste
vesicle in plants disposal, water balance, cell
growth, and protection
Concept 6.5 Mitochondrion Bounded by double Cellular respiration
Mitochondria and chloro- membrane;
plasts change energy from inner membrane has
one form to another infoldings (cristae)
Chloroplast Typically two membranes Photosynthesis
around fluid stroma, which
contains membranous thylakoids
stacked into grana (in plants)
Peroxisome Specialized metabolic Contains enzymes that transfer
compartment bounded by a hydrogen to water, producing
single membrane hydrogen peroxide (H2O2) as a
by-product, which is converted
to water by other enzymes
in the peroxisome