1. Protists, fungi, animals, and plants all consist of eukaryotic cells
Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions
The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic
Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells
Protists, fungi, animals, and plants all consist of eukaryotic cells
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2. Comparing Prokaryotic and Eukaryotic Cells
Basic features of all cells:
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)
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3. Prokaryotic cells are characterized by having No nucleus
DNA in an unbound region called the nucleoid
No membrane-bound organelles
Cytoplasm bound by the plasma membrane
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4. Eukaryotic cells are characterized by having
DNA in a nucleus that is bounded by a membranous nuclear envelope
Membrane-bound organelles
Cytoplasm in the region between the plasma membrane and nucleus
Eukaryotic cells are generally much larger than prokaryotic cells
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5. ENDOPLASMIC RETICULUM (ER) Nucleolus NUCLEUS Rough ER Smooth ER
Fig. 6-9a
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Nucleolus
NUCLEUS
Rough ER
Smooth ER
Flagellum
Chromatin
Centrosome
Plasma membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Figure 6.9 Animal and plant cells—animal cell
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome

6. Rough endoplasmic reticulum
Fig. 6-9b
Nuclear envelope
Rough endoplasmic reticulum
NUCLEUS
Nucleolus
Chromatin
Smooth endoplasmic reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate filaments
CYTO-
SKELETON
Microtubules
Figure 6.9 Animal and plant cells—plant cell
Mitochondrion
Peroxisome
Chloroplast
Plasma membrane
Cell wall
Plasmodesmata
Wall of adjacent cell

7. Fig. 6-UN1a Cell Component Structure Function Concept 6.3 Nucleus
Surrounded by nuclear
envelope (double membrane)
perforated by nuclear pores.
The nuclear envelope is
continuous with the
endoplasmic reticulum (ER).
Houses chromosomes, made of
chromatin (DNA, the genetic
material, and proteins); contains
nucleoli, where ribosomal
subunits are made. Pores
regulate entry and exit os
materials.
The eukaryotic cell’s genetic
instructions are housed in
the nucleus and carried out
by the ribosomes
(ER)
Ribosome
Two subunits made of ribo-
somal RNA and proteins; can be
free in cytosol or bound to ER
Protein synthesis

8. Fig. 6-UN1b Cell Component Structure Function Concept 6.4
Endoplasmic reticulum
Extensive network of
membrane-bound tubules and
sacs; membrane separates
lumen from cytosol;
continuous with
the nuclear envelope.
Smooth ER: synthesis of
lipids, metabolism of carbohy-
drates, Ca2+ storage, detoxifica-
tion of drugs and poisons
The endomembrane system
regulates protein traffic and
performs metabolic functions
in the cell
(Nuclear
envelope)
Rough ER: Aids in sythesis of
secretory and other proteins
from bound ribosomes; adds
carbohydrates to glycoproteins;
produces new membrane
Golgi apparatus
Stacks of flattened
membranous
sacs; has polarity
(cis and trans
faces)
Modification of proteins, carbo-
hydrates on proteins, and phos-
pholipids; synthesis of many
polysaccharides; sorting of
Golgi products, which are then
released in vesicles.
Breakdown of ingested sub-
stances cell macromolecules, and damaged organelles for recycling
Lysosome
Membranous sac of hydrolytic
enzymes (in animal cells)
Vacuole
Large membrane-bounded
vesicle in plants
Digestion, storage, waste
disposal, water balance, cell
growth, and protection

9. Fig. 6-UN1c Cell Component Structure Function Concept 6.5
Mitochondrion
Bounded by double
membrane;
inner membrane has
infoldings (cristae)
Cellular respiration
Mitochondria and chloro-
plasts change energy from
one form to another
Chloroplast
Typically two membranes
around fluid stroma, which
contains membranous thylakoids
stacked into grana (in plants)
Photosynthesis
Peroxisome
Specialized metabolic
compartment bounded by a
single membrane
Contains enzymes that transfer
hydrogen to water, producing
hydrogen peroxide (H2O2) as a
by-product, which is converted
to water by other enzymes
in the peroxisome

10. The nucleus contains most of the DNA in a eukaryotic cell
Concept 6.3: The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
The nucleus contains most of the DNA in a eukaryotic cell
Ribosomes use the information from the DNA to make proteins
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11. The Nucleus: Information Central
The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle
The nuclear envelope encloses the nucleus, separating it from the cytoplasm
The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer
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12. Close-up of nuclear envelope
Fig. 6-10
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore complex
Rough ER
Surface of
nuclear envelope
Ribosome
1 µm
Figure 6.10 The nucleus and its envelope
0.25 µm
Close-up of nuclear envelope
Pore complexes (TEM)
Nuclear lamina (TEM)

13. 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
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14. Chromatin condenses to form discrete chromosomes
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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15. Ribosomes: Protein Factories
Ribosomes are particles made of ribosomal RNA and protein
Ribosomes carry out protein synthesis in two locations:
In the cytosol (free ribosomes)
On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)
For the Cell Biology Video Staining of Endoplasmic Reticulum, go to Animation and Video Files.
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16. Endoplasmic reticulum (ER)
Fig. 6-11
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large subunit
Figure 6.11 Ribosomes
Small subunit
0.5 µm
TEM showing ER and ribosomes
Diagram of a ribosome

17. Components of the endomembrane system:
Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell
Components of the endomembrane system:
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
These components are either continuous or connected via transfer by vesicles
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18. The Endoplasmic Reticulum: Biosynthetic Factory
The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells
The ER membrane is continuous with the nuclear envelope
There are two distinct regions of ER:
Smooth ER, which lacks ribosomes
Rough ER, with ribosomes studding its surface
For the Cell Biology Video ER and Mitochondria in Leaf Cells, go to Animation and Video Files.
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19. Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER
Fig. 6-12
Smooth ER
Nuclear envelope
Rough ER
ER lumen
Cisternae
Transitional ER
Ribosomes
Transport vesicle
200 nm
Smooth ER
Rough ER
Figure 6.12 Endoplasmic reticulum (ER)

20. Functions of Smooth ER The smooth ER Synthesizes lipids
Metabolizes carbohydrates
Detoxifies poison
Stores calcium
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21. Functions of Rough ER The rough ER
Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)
Distributes transport vesicles, proteins surrounded by membranes
Is a membrane factory for the cell
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22. The Golgi Apparatus: Shipping and Receiving Center
The Golgi apparatus consists of flattened membranous sacs called cisternae
Functions of the Golgi apparatus:
Modifies products of the ER
Manufactures certain macromolecules
Sorts and packages materials into transport vesicles
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23. (“receiving” side of Golgi apparatus) 0.1 µm
Fig. 6-13
cis face
(“receiving” side of Golgi apparatus)
0.1 µm
Cisternae
Figure 6.13 The Golgi apparatus
trans face
(“shipping” side of Golgi apparatus)
TEM of Golgi apparatus

24. Lysosomes: Digestive Compartments
A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules
Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids
Animation: Lysosome Formation
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25. A lysosome fuses with the food vacuole and digests the molecules
Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole
A lysosome fuses with the food vacuole and digests the molecules
Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy
For the Cell Biology Video Phagocytosis in Action, go to Animation and Video Files.
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26. two damaged organelles 1 µm
Fig. 6-14
Nucleus
1 µm
Vesicle containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Digestive
enzymes
Lysosome
Lysosome
Plasma
membrane
Peroxisome
Figure 6.14a Lysosomes
Digestion
Food vacuole
Mitochondrion
Digestion
Vesicle
(a) Phagocytosis
(b) Autophagy

27. Nucleus 1 µm Lysosome Digestive enzymes Lysosome Plasma membrane
Fig. 6-14a
Nucleus
1 µm
Lysosome
Digestive enzymes
Lysosome
Figure 6.14a Lysosome—phagocytosis
Plasma membrane
Digestion
Food vacuole
(a) Phagocytosis

28. two damaged organelles 1 µm
Fig. 6-14b
Vesicle containing
two damaged organelles
1 µm
Mitochondrion fragment
Peroxisome fragment
Lysosome
Figure 6.14b Lysosomes—autophagy
Peroxisome
Mitochondrion
Digestion
Vesicle
(b) Autophagy

29. Vacuoles: Diverse Maintenance Compartments
A plant cell or fungal cell may have one or several vacuoles
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30. Video: Paramecium Vacuole
Food vacuoles are formed by phagocytosis
Contractile vacuoles, found in many freshwater protists, pump excess water out of cells
Central vacuoles, found in many mature plant cells, hold organic compounds and water
Video: Paramecium Vacuole
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31. Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast
Fig. 6-15
Central vacuole
Cytosol
Nucleus
Central vacuole
Figure 6.15 The plant cell vacuole
Cell wall
Chloroplast
5 µm

32. The Endomembrane System: A Review
The endomembrane system is a complex and dynamic player in the cell’s compartmental organization
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33. Nucleus Rough ER Smooth ER Plasma membrane Fig. 6-16-1
Figure 6.16 Review: relationships among organelles of the endomembrane system
Plasma membrane

34. Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi
Fig
Nucleus
Rough ER
Smooth ER
cis Golgi
Figure 6.16 Review: relationships among organelles of the endomembrane system
Plasma membrane
trans Golgi

35. Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi
Fig
Nucleus
Rough ER
Smooth ER
cis Golgi
Figure 6.16 Review: relationships among organelles of the endomembrane system
Plasma membrane
trans Golgi

36. Peroxisomes are oxidative organelles
Concept 6.5: Mitochondria and chloroplasts change energy from one form to another
Mitochondria are the sites of cellular respiration, a metabolic process that generates ATP
Chloroplasts, found in plants and algae, are the sites of photosynthesis
Peroxisomes are oxidative organelles
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For the Cell Biology Video Mitochondria in 3D, go to Animation and Video Files.
For the Cell Biology Video Chloroplast Movement, go to Animation and Video Files.
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37. Mitochondria and chloroplasts
Are NOT part of the endomembrane system
Have a double membrane
Have proteins made by free ribosomes
Contain their own DNA
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38. Mitochondria: Chemical Energy Conversion
Mitochondria are in nearly all eukaryotic cells
They have a smooth outer membrane and an inner membrane folded into cristae
The inner membrane creates two compartments: intermembrane space and mitochondrial matrix
Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix
Cristae present a large surface area for enzymes that synthesize ATP
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39. in the mitochondrial matrix
Fig. 6-17
Intermembrane space
Outer membrane
Free ribosomes
in the mitochondrial matrix
Inner membrane
Cristae
Figure 6.17 The mitochondrion, site of cellular respiration
Matrix
0.1 µm

40. Chloroplasts: Capture of Light Energy
The chloroplast is a member of a family of organelles called plastids
Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis
Chloroplasts are found in leaves and other green organs of plants and in algae
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41. Chloroplast structure includes:
Thylakoids, membranous sacs, stacked to form a granum
Stroma, the internal fluid
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42. Inner and outer membranes
Fig. 6-18
Ribosomes
Stroma
Inner and outer membranes
Granum
1 µm
Thylakoid
Figure 6.18 The chloroplast, site of photosynthesis

43. Peroxisomes: Oxidation
Peroxisomes are specialized metabolic compartments bounded by a single membrane
Peroxisomes produce hydrogen peroxide and convert it to water
Oxygen is used to break down different types of molecules
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44. Chloroplast Peroxisome Mitochondrion 1 µm Fig. 6-19
Figure 6.19 A peroxisome
1 µm

45. Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell
The cytoskeleton is a network of fibers extending throughout the cytoplasm
Three main types of fibers make up the cytoskeleton:
Microtubules are the thickest of the three components of the cytoskeleton
Microfilaments, also called actin filaments, are the thinnest components
Intermediate filaments are fibers with diameters in a middle range
For the Cell Biology Video The Cytoskeleton in a Neuron Growth Cone, go to Animation and Video Files
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46. 10 µm Column of tubulin dimers Tubulin dimer   25 nm Table 6-1a

47. Table 6-1b
10 µm
Table 6-1b
Actin subunit
7 nm

48. Fibrous subunit (keratins coiled together)
Table 6-1c
5 µm
Table 6-1c
Keratin proteins
Fibrous subunit (keratins
coiled together)
8–12 nm

49. Functions of microtubules:
Microtubules are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long
Functions of microtubules:
Shaping the cell (centrosome)
Guiding movement of organelles
Separating chromosomes during cell division (centrioles)
For the Cell Biology Video Transport Along Microtubules, go to Animation and Video Files.
For the Cell Biology Video Movement of Organelles in Vivo, go to Animation and Video Files.
For the Cell Biology Video Movement of Organelles in Vitro, go to Animation and Video Files.
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50. Longitudinal section of one centriole Microtubules Cross section
Fig. 6-22
Centrosome
Microtubule
Centrioles
0.25 µm
Figure 6.22 Centrosome containing a pair of centrioles
Longitudinal section of one centriole
Microtubules
Cross section
of the other centriole

51. Video: Paramecium Cilia
Cilia and Flagella
Microtubules control the beating of cilia and flagella, locomotor appendages of some cells
Cilia (oars on a boat) and flagella (undulating) differ in their beating patterns
Video: Chlamydomonas
Video: Paramecium Cilia
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52. Direction of organism’s movement
Fig. 6-23
Direction of swimming
(a) Motion of flagella
5 µm
Direction of organism’s movement
Figure 6.23a A comparison of the beating of flagella and cilia—motion of flagella
Power stroke
Recovery stroke
(b) Motion of cilia
15 µm

53. Animation: Cilia and Flagella
Cilia and flagella share a common ultrastructure:
A core of microtubules sheathed by the plasma membrane (9+2 arrangement)
A basal body that anchors the cilium or flagellum (Like centriole)
A motor protein called dynein, which drives the bending movements of a cilium or flagellum
Animation: Cilia and Flagella
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54. Cross section of cilium
Fig. 6-24
Outer microtubule doublet
Plasma membrane
0.1 µm
Dynein proteins
Central microtubule
Radial spoke
Protein cross-linking outer doublets
Microtubules
(b)
Cross section of cilium
Plasma membrane
Basal body
0.5 µm
(a)
Longitudinal section of cilium
0.1 µm
Figure 6.24 Ultrastructure of a eukaryotic flagellum or motile cilium
Triplet
(c) Cross section of basal body

55. Microfilaments (Actin Filaments)
Microfilaments are solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits
The structural role of microfilaments is to bear tension, resisting pulling forces within the cell
Microfilaments that function in cellular motility contain the protein myosin in addition to actin
In muscle cells, thousands of actin filaments are arranged parallel to one another
Thicker filaments composed of myosin interdigitate with the thinner actin fibers
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56. Figure 6.27 Microfilaments and motility
Muscle cell
Actin filament
Myosin filament
Myosin arm
(a) Myosin motors in muscle cell contraction
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
Extending
pseudopodium
(b) Amoeboid movement
Nonmoving cortical
cytoplasm (gel)
Figure 6.27 Microfilaments and motility
Chloroplast
Streaming
cytoplasm
(sol)
Vacuole
Parallel actin
filaments
Cell wall
(c) Cytoplasmic streaming in plant cells

57. Intermediate Filaments
Intermediate filaments range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules
They support cell shape and fix organelles in place
Intermediate filaments are more permanent cytoskeleton fixtures than the other two classes
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For the Cell Biology Video Microtubule Sliding in Flagellum Movement, go to Animation and Video Files.
For the Cell Biology Video Microtubule Dynamics, go to Animation and Video Files.
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58. These extracellular structures include:
Concept 6.7: Extracellular components and connections between cells help coordinate cellular activities
Most cells synthesize and secrete materials that are external to the plasma membrane
These extracellular structures include:
Cell walls of plants
The extracellular matrix (ECM) of animal cells
Intercellular junctions
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59. Secondary cell wall Primary cell wall Middle lamella Central vacuole
Fig. 6-28
Secondary cell wall
Primary cell wall
Middle lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Figure 6.28 Plant cell walls
Plant cell walls
Plasmodesmata

60. Prokaryotes, fungi, and some protists also have cell walls
Cell Walls of Plants
The cell wall is an extracellular structure that distinguishes plant cells from animal cells
Prokaryotes, fungi, and some protists also have cell walls
The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water
Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
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61. 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
Plasmodesmata are channels between adjacent plant cells
Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
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62. Proteoglycan complex Collagen EXTRACELLULAR FLUID Fibronectin
Fig. 6-30a
Collagen
Proteoglycan complex
EXTRACELLULAR FLUID
Fibronectin
Integrins
Plasma membrane
Figure 6.30 Extracellular matrix (ECM) of an animal cell, part 1
Micro-filaments
CYTOPLASM

63. The Extracellular Matrix (ECM) of Animal Cells
Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)
The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin
ECM proteins bind to receptor proteins in the plasma membrane called integrins
Functions of the ECM:
Support
Adhesion
Movement
Regulation
For the Cell Biology Video Cartoon Model of a Collagen Triple Helix, go to Animation and Video Files.
For the Cell Biology Video Staining of the Extracellular Matrix, go to Animation and Video Files.
For the Cell Biology Video Fibronectin Fibrils, go to Animation and Video Files.
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64. 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
Tight junctions
Desmosomes
Gap junctions
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65. Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells
At 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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