1. Fig. 6-1
Figure 6.1 How do cellular components cooperate to help the cell function?

2. Key Cell Concepts
Eukaryotic cells have internal membranes that compartmentalize their functions
The eukaryotic cell′s genetic instructions are housed in the nucleus and carried out by the ribosomes
The endomembrane system regulates protein traffic and performs metabolic functions in the cell
Mitochondria and chloroplasts change energy from one form to another
The cytoskeleton is a network of fibers that organizes structures and activities in the cell
Extracellular components and connections between cells help coordinate cellular activities

3. Overview: The Fundamental Units of Life
All organisms are made of cells
The cell is the simplest collection of matter that can live
Cell structure is correlated to cellular function
All cells are related by their descent from earlier cells
For the Discovery Video Cells, go to Animation and Video Files.
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4. 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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5. 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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6. 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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7. A typical rod-shaped bacterium (b)
Fig. 6-6
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
Flagella
(a)
A typical rod-shaped bacterium
(b)
A thin section through the bacterium Bacillus coagulans (TEM)
Figure 6.6 A prokaryotic cell

8. 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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9. The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
The general structure of a biological membrane is a double layer of phospholipids
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10. Carbohydrate side chain
Fig. 6-7
(a)
TEM of a plasma
membrane
Outside of cell
Inside of
cell
0.1 µm
Carbohydrate side chain
Hydrophilic
region
Figure 6.7 The plasma membrane
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane

11. The surface area to volume ratio of a cell is critical
The logistics of carrying out cellular metabolism sets limits on the size of cells
The surface area to volume ratio of a cell is critical
As the surface area increases by a factor of n2, the volume increases by a factor of n3
Small cells have a greater surface area relative to volume
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12. Surface area increases while total volume remains constant
Fig. 6-8
Surface area increases while
total volume remains constant 5 1 1
Total surface area
[Sum of the surface areas
(height  width) of all boxes
sides  number of boxes] 6
150
750
Total volume
[height  width  length 
number of boxes]
Figure 6.8 Geometric relationships between surface area and volume 1
125
125
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume] 6
1.2 6

13. A Panoramic View of the Eukaryotic Cell
A eukaryotic cell has internal membranes that partition the cell into organelles
Plant and animal cells have most of the same organelles
BioFlix: Tour Of An Animal Cell
BioFlix: Tour Of A Plant Cell
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14. 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

15. 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

16. 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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17. 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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18. 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)

19. 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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20. 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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21. 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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22. 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

23. 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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24. 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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25. 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)

26. Functions of Smooth ER The smooth ER Synthesizes lipids
Metabolizes carbohydrates
Detoxifies poison
Stores calcium
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27. 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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28. 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
For the Cell Biology Video ER to Golgi Traffic, go to Animation and Video Files.
For the Cell Biology Video Golgi Complex in 3D, go to Animation and Video Files.
For the Cell Biology Video Secretion From the Golgi, go to Animation and Video Files.
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29. (“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

30. 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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31. 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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32. 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

33. 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

34. 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

35. Vacuoles: Diverse Maintenance Compartments
A plant cell or fungal cell may have one or several vacuoles
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36. 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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37. 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

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

40. 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

41. 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

42. 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
For the Cell Biology Video ER and Mitochondria in Leaf Cells, go to Animation and Video Files.
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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43. 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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44. 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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45. 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

46. 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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47. Chloroplast structure includes:
Thylakoids, membranous sacs, stacked to form a granum
Stroma, the internal fluid
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48. 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

49. 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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50. Chloroplast Peroxisome Mitochondrion 1 µm Fig. 6-19
Figure 6.19 A peroxisome
1 µm

51. It is composed of three types of molecular structures:
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
It organizes the cell’s structures and activities, anchoring many organelles
It is composed of three types of molecular structures:
Microtubules
Microfilaments
Intermediate filaments
For the Cell Biology Video The Cytoskeleton in a Neuron Growth Cone, go to Animation and Video Files
For the Cell Biology Video Cytoskeletal Protein Dynamics, go to Animation and Video Files.
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52. Microtubule Microfilaments 0.25 µm Fig. 6-20
Figure 6.20 The cytoskeleton
Microfilaments
0.25 µm

53. Roles of the Cytoskeleton: Support, Motility, and Regulation
The cytoskeleton helps to support the cell and maintain its shape
It interacts with motor proteins to produce motility
Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton
Recent evidence suggests that the cytoskeleton may help regulate biochemical activities
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54. Receptor for motor protein
Fig. 6-21
Vesicle
ATP
Receptor for motor protein
Motor protein (ATP powered)
Microtubule
of cytoskeleton
(a)
Microtubule
Vesicles
0.25 µm
Figure 6.21 Motor proteins and the cytoskeleton
(b)

55. Components of the Cytoskeleton
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 Actin Network in Crawling Cells, go to Animation and Video Files.
For the Cell Biology Video Actin Visualization in Dendrites, go to Animation and Video Files.
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56. 10 µm Column of tubulin dimers Tubulin dimer   25 nm Table 6-1a

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

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

59. Video: Paramecium Cilia
Cilia and Flagella
Microtubules control the beating of cilia and flagella, locomotor appendages of some cells
Cilia and flagella differ in their beating patterns
Video: Chlamydomonas
Video: Paramecium Cilia
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60. 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

61. 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
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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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. Functions of the ECM: Support Adhesion Movement Regulation
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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. Plasmodesmata in Plant Cells
Plasmodesmata are channels that perforate plant cell walls
Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
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66. Cell walls Interior of cell Interior of cell 0.5 µm Plasmodesmata
Fig. 6-31
Cell walls
Interior of cell
Interior of cell
Figure 6.31 Plasmodesmata between plant cells
0.5 µm
Plasmodesmata
Plasma membranes

67. 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
Animation: Tight Junctions
Animation: Desmosomes
Animation: Gap Junctions
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68. Fig. 6-32 Tight junction Tight junctions prevent fluid from moving
across a layer of cells
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
Desmosome
Gap
junctions
1 µm
Figure 6.32 Intercellular junctions in animal tissues
Extracellular
matrix
Space
between
cells
Gap junction
Plasma membranes
of adjacent cells
0.1 µm

69. The Cell: A Living Unit Greater Than the Sum of Its Parts
Cells rely on the integration of structures and organelles in order to function
For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane
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70. Fig. 6-33
5 µm
Figure 6.33 The emergence of cellular functions

71. You should now be able to:
Distinguish between the following pairs of terms: magnification and resolution; prokaryotic and eukaryotic cell; free and bound ribosomes; smooth and rough ER
Describe the structure and function of the components of the endomembrane system
Briefly explain the role of mitochondria, chloroplasts, and peroxisomes
Describe the functions of the cytoskeleton
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72. Describe four different intercellular junctions
Compare the structure and functions of microtubules, microfilaments, and intermediate filaments
Describe the structure and roles of the extracellular matrix in animal cells
Describe four different intercellular junctions
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