1. A Tour of the Cell Chapter 6
(modified: 38 illustrations, 78 slides total )

2. 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 and cell function are related
All cells come from earlier cells
For the Discovery Video Cells, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Light microscope is the simplest
Concept 6.1: To study cells, biologists use microscopes and the tools of biochemistry
Microscopes are used to see cells and the complex details of cells invisible to the unaided eye
Light microscope is the simplest
In a light microscope (LM), visible light passes through a specimen and then through glass lenses, magnifying the image
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

4. The quality of an image depends on
Magnification- ratio of an object’s image size to its real size
Resolution- measure of the image’s clarity, or the minimum distance between two distinguishable points
Contrast- visible differences in parts of the sample
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5. Limitations of the light and electron microscopes
Fig. 6-2
10 m
Human height
1 m
Length of some nerve and muscle cells
0.1 m
Unaided eye
Chicken egg
1 cm
Frog egg
1 mm
100 µm
Limitations of the light and electron microscopes
Most plant and animal cells
Light microscope
10 µm
Nucleus
Most bacteria
1 µm
Mitochondrion
Figure 6.2 The size range of cells
Smallest bacteria
Electron microscope
100 nm
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms

6. LM’s effectively magnify a specimen’s image to about 1,000 times its actual size.
Various techniques increase contrast and help cell components to be stained or labeled
Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LM
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7. (e) Fluorescence TECHNIQUE RESULTS TECHNIQUE RESULTS Brightfield
(unstained
specimen)
(e) Fluorescence
100 µm
(f) Confocal
(b) Brightfield (stained
specimen)
Figure 6.3 Light microscopy
(c) Phase-contrast
100 µm
(d) Differential-
interference-
contrast (Nomarski)
Fig. 6-3

8. Electron microscopes (EMs) are used to study subcellular structures
Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, giving images that look 3-D
Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen to study the internal structure of cells
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9. (b) Transmission electron microscopy (TEM) Longitudinal section of
Fig. 6-4
TECHNIQUE
RESULTS
1 µm
(a) Scanning electron
microscopy (SEM)
Cilia
(b) Transmission electron
microscopy (TEM)
Longitudinal
section of
cilium
Cross section
of cilium
1 µm
Figure 6.4 Electron microscopy

10. This lets scientists determine the functions of organelles
Cell Fractionation
Cell fractionation breaks cells and separates major organelles from each other using ultracentrifuges
This lets scientists determine the functions of organelles
Biochemistry and cytology help correlate cell function with structure
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11. Differential centrifugation
Fig. 6-5a
TECHNIQUE
Homogenization
Figure 6.5 Cell fractionation, part 1
Tissue
cells
Homogenate
Differential centrifugation

12. (1,000 times the force of gravity)
Fig. 6-5b
TECHNIQUE (cont.)
1,000 g
(1,000 times the force of gravity)
10 min
Supernatant poured into next tube
20,000 g
20 min
80,000 g
60 min
Pellet rich in nuclei and cellular debris
150,000 g
3 hr
Pellet rich in mitochondria (and chloro-plasts if cells
are from a plant)
Figure 6.5 Cell fractionation, part 2
Pellet rich in “microsomes” (pieces of plasma
membranes and cells’ internal membranes)
Pellet rich in ribosomes

13. All cells are either prokaryotic or eukaryotic cells
Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions
All cells are either prokaryotic or eukaryotic cells
Bacteria & Archaeabacteria are prokaryotic cells
Protists, fungi, animals, and plants are eukaryotic cells
Basic features of all cells:
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)
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14. Comparing Prokaryotic and Eukaryotic Cells
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
Eukaryotic cells are much larger than prokaryotic cells and are characterized by:
A membrane-bound nucleus containing the DNA
Membrane-bound organelles
Cytoplasm between the plasma membrane and nucleus
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. 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

16. Cellular Membranes
The plasma membrane is a selective barrier allowing passage of oxygen, nutrients, and waste to feed & clean the volume of a cell
Nearly all biological membrane consist of a double layer of phospholipids
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17. 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

18. Size limitations in a cell
The surface area to volume ratio of a cell sets limits on size because cells depend on diffusion for nutrition & waste removal
As the surface area increases by a factor of n2, the volume increases by n3
So, small cells have a greater surface area relative to their volume
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19. 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

20. BioFlix: Tour Of An Animal Cell BioFlix: Tour Of A Plant Cell
Concept 6.3: The eukaryotic cell’s genetic info. is housed in the nucleus and carried out by ribosomes
A eukaryotic cell has internal membranes that partition the cell into organelles
Plant and animal cells have almost the same organelles
The nucleus contains most of the DNA in a eukaryotic cell
Ribosomes use the information from the DNA to make proteins
BioFlix: Tour Of An Animal Cell
BioFlix: Tour Of A Plant Cell
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21. 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

22. 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

23. The Nucleus: Information Central
Nucleus- holds most genes; usually largest organelle
Nuclear envelope (membrane)- encloses nucleus, separates it from cytoplasm; is a double membrane; each membrane is a lipid bilayer
Pores regulate entry/exit of molecules from the nucleus
Nuclear lamina maintains shape of the nucleus; composed of protein
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24. 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)

25. DNA and proteins form genetic material called chromatin
Chromatin condenses to form chromosomes
Nucleolus- an area within the nucleus; the site of ribosomal RNA (rRNA) synthesis
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26. Ribosomes: Protein Factories
Ribosomes- particles made of rRNA & protein
Ribosomes carry out protein synthesis in two locations:
In cytosol (free ribosomes)
On 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. 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

28. Components of the endomembrane system:
Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions
Components of the endomembrane system:
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
The components are either continuous or connected via transfer by vesicles
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. The Endoplasmic Reticulum: Biosynthetic Factory
Endoplasmic reticulum (ER) is more than half the total membrane in most eukaryotic cells
The ER is continuous with the nuclear envelope
Two distinct regions:
Smooth ER- no ribosomes
Rough ER- has ribosomes on its surface
For the Cell Biology Video ER and Mitochondria in Leaf Cells, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

30. 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)

31. Functions of Smooth & Rough ER
Smooth ER
Synthesizes lipids
Metabolizes carbohydrates
Detoxifies poison
Stores calcium
The rough ER
Has bound ribosomes to secrete glycoproteins (proteins covalently bonded to carbohydrates)
Distributes transport vesicles, proteins surrounded by membranes
Is a membrane factory for the cell
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

32. The Golgi Apparatus: Shipping and Receiving Center
Golgi apparatus- group of flattened membranous sacs called cisternae
Functions of the Golgi apparatus:
Modifies products of 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

33. (“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

34. Lysosomes: Digestive Compartments
Lysosome- membranous sac of hydrolytic enzymes that digest macromolecules
Lysosomal enzymes hydrolyze proteins, fats, polysaccharides, & nucleic acids
Phagocytosis- when certain cells can engulf another cell to form a food vacuole
A lysosome fuses with the food vacuole and digests the molecules
Autophagy- lysosomes also use enzymes to recycle old organelles and macromolecules
Animation: Lysosome Formation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

35. 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

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

39. Chloroplasts- plants & algae; sites of photosynthesis
Concept 6.5: Mitochondria and chloroplasts change energy from one form to another
Mitochondria- sites of cellular respiration, a metabolic process that generates ATP
Chloroplasts- plants & algae; sites of photosynthesis
Peroxisomes- oxidative organelles; break down free radicles
Mitochondria and chloroplasts
Are not part of the endomembrane system
Have a double membrane
Have proteins made by free ribosomes
Contain their own DNA
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

40. Mitochondria: Chemical Energy Conversion
Mitochondria are in nearly all eukaryotic cells
2 membranes
Outer membrane
Cristae- inner, folded membrane
Cristae create two compartments:
intermembrane space
mitochondrial matrix- where some metabolic steps of cell respiration are catalyzed
Cristae present a large surface area for enzymes that synthesize ATP
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

41. 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

42. Chloroplasts: Capture of Light Energy
Chloroplast are
plastids- pigment containing organelles
found in leaves & green organs of plants & algae
Chloroplasts contain
Chlorophyll- a green pigment
Enzymes & molecules that function in photosynthesis
Chloroplast structures include:
Thylakoids, membranous sacs, stacked to form a granum
Stroma, the internal fluid
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43. Chloroplast Structure
Fig. 6-18
Chloroplast Structure
Ribosomes
Thylakoid
Stroma
Granum
Inner and outer membranes
1 µm
Figure 6.18 The chloroplast, site of photosynthesis

44. Peroxisomes: Oxidation- Single membrane
Peroxisomes are specialized metabolic compartments
bounded by a single membrane
produce hydrogen peroxide &convert it to water
Liberate oxygen as a by product
Oxygen is used to break down different types of molecules
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45. Relative sizes of organelles
Fig. 6-19
Chloroplast
Peroxisome
Mitochondrion
Relative sizes of organelles
Figure 6.19 A peroxisome
1 µm

46. Cytoskeleton- network of fibers extending throughout the cytoplasm
Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell
Cytoskeleton- network of fibers extending throughout the cytoplasm
organizes the cell’s structures and activities
anchors many organelles
Three main types of fibers in the cytoskeleton:
Microtubules- thickest fiber of the cytoskeleton
Microfilaments- also called actin filaments; thinnest components
Intermediate filaments- fibers with diameters in a mid-range
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

47. Microtubule Microfilaments 0.25 µm Fig. 6-20
Figure 6.20 The cytoskeleton
Microfilaments
0.25 µm

48. Roles of a Cytoskeleton: Support, Motility, Regulation
Cytoskeleton- supports cell & maintains its shape
It interacts with motor proteins to create motility
In cells, vesicles move on cytoskeleton monorails
Cytoskeletons may regulate biochem. Activities
Microtubules- hollow rods ~ 25 nm in diameter & ~ 200 nm to 25 microns long
Functions of microtubules:
Shaping the cell
Guiding movement of organelles
Separating chromosomes during cell division
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49. 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)

50. 10 µm Column of tubulin dimers Tubulin dimer   25 nm Table 6-1a

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

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

53. Centrosomes & Centrioles; Cilia & Flagella
Centrosome- a “microtubule-organizing center”
In many cells, microtubules grow out from a centrosome near the nucleus
In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring
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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54. 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

55. 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

56. Animation: Cilia and Flagella
Cilia and flagella share a common ultrastructure:
Core of microtubules sheathed by the plasma membrane
Basal body- anchors the cilium or flagellum
Motor protein called dynein, which drives the bending movements of a cilium or flagellum
Animation: Cilia and Flagella
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57. 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

58. How dynein “walking” moves flagella and cilia:
Dynein arms alternately grab, move, and release the outer microtubules
Protein cross-links limit sliding
Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum
For the Cell Biology Video Motion of Isolated Flagellum, go to Animation and Video Files.
For the Cell Biology Video Flagellum Movement in Swimming Sperm, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

59. How dynein “walking” moves flagella and cilia
Fig. 6-25
Microtubule doublets
Dynein
protein
ATP
(a) Effect of unrestrained dynein movement
Cross-linking proteins
inside outer doublets
Anchorage
in cell
(b) Effect of cross-linking proteins 1 3 2
(c) Wavelike motion
How dynein “walking” moves flagella and cilia
Figure 6.25 How dynein “walking” moves flagella and cilia

60. Microfilaments (Actin Filaments)
Microfilaments- twisted double chain of actin subunits forming solid rods ~ 7 nm in diameter
Microfilaments form a 3-D network, the cortex, just inside the plasma membrane to:
bear tension
resist pulling forces within the cell
support the cell’s shape
Bundles of microfilaments form the core of microvilli on intestinal cells
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61. Microfilaments (actin filaments)
Fig. 6-26
Microvillus
Plasma membrane
Microfilaments (actin filaments)
Figure 6.26 A structural role of microfilaments
Intermediate filaments
0.25 µm

62. Microfilaments used in motility have myosin & actin.
Uses of Actin & Myosin
Microfilaments used in motility have myosin & actin.
In muscle cells- the “myosin motor”
thousands of actin filaments are arranged parallel
Thicker myosin filaments inter-layer with thinner actin fibers
Muscles contract when fibers slide past each other
In ameba- in pseudopods (cellular extensions)
Actin and myosin contraction drives amoeboid movement
Actin subunits assemble into microfilaments and contract; & then disassemble
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63. Muscle cell Actin filament Myosin filament Myosin arm
Fig, 6-27a
Muscle cell
Actin filament
Myosin filament
Myosin arm
Figure 6.27a Microfilaments and motility
(a) Myosin motors in muscle cell contraction

64. Cortex (outer cytoplasm): gel with actin network
Fig. 6-27bc
Cortex (outer cytoplasm): gel with actin network
Inner cytoplasm: sol with actin subunits
Extending pseudopodium
(b) Amoeboid movement
Nonmoving cortical cytoplasm (gel)
Chloroplast
Streaming cytoplasm (sol)
Figure 6.27b,c Microfilaments and motility
Vacuole
Parallel actin filaments
Cell wall
(c) Cytoplasmic streaming in plant cells

65. Video: Cytoplasmic Streaming
Cytoplasmic streaming- circular flow of cytoplasm within cells
Streaming distributes materials within the cell
In plants, actin-myosin interactions & sol-gel transformations drive streaming
Intermediate filaments
range in diameter from 8–12 nanometers;
In size, microtubules>intermediate filaments > microfilaments
support cell shape & fix organelles in place
are more permanent than the other 2 classes
Video: Cytoplasmic Streaming
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66. Cells make and secrete materials external to the plasma membrane
Concept 6.7: Extracellular components & connections between cells coordinate cellular activities
Cells make and secrete materials external to the plasma membrane
Extracellular structures include:
Plant cell walls
Extracellular matrix (ECM) of animal cells
Intercellular junctions
For the Cell Biology Video Ciliary Motion, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

67. Cell wall are extracellular structures Cell walls
Cell Walls of Plants
Plants, prokaryotes, fungi, and some protists all have cell walls; animal cells don’t
Cell wall are extracellular structures
Cell walls
protect plant cells
maintain their shape
prevents excessive water uptake
Plant cell walls are of cellulose fibers embedded in polysaccharides and protein
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

68. 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- channels between adjacent plant cells
For the Cell Biology Video E-cadherin Expression, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

69. 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

70. The Extracellular Matrix (ECM) of Animal Cells
Animal cells are covered by an extracellular matrix (ECM)
ECM- made of glycoproteins like collagen, proteoglycans, and fibronectin
ECM proteins bind to integrins- receptor proteins in the plasma membrane
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

71. Figure 6.30 Extracellular matrix (ECM) of an animal cell, part 1
EXTRACELLULAR FLUID
Collagen
Fibronectin
Plasma
membrane
Micro-
filaments
CYTOPLASM
Integrins
Proteoglycan
complex
Polysaccharide
molecule
Carbo-
hydrates
Core
protein
Proteoglycan complex
Figure 6.30 Extracellular matrix (ECM) of an animal cell, part 1

72. Intercellular Junctions
Neighboring cells in tissues, etc. will adhere, interact, and communicate through direct contact
Intercellular junctions aid this contact
Types of intercellular junctions:
Plasmodesmata
Tight junctions
Desmosomes
Gap junctions
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73. Plasmodesmata in Plant Cells
Plasmodesmata-channels in plant cell walls
Through these, water, small solutes, proteins and RNA can pass from cell to cell
Interior of cell
0.5 µm
Plasmodesmata
Plasma membranes
Cell walls
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74. Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells
Tight junctions- membranes of neighboring cells pressed together; prevents leakage of extracellular fluid
Desmosomes (anchoring junctions) fasten cells together into strong sheets
Gap junctions (communicating junctions) make cytoplasmic channels between adjacent cells
Animation: Tight Junctions
Animation: Desmosomes
Animation: Gap Junctions
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

75. Figure 6.32 Intercellular junctions in animal tissues
Tight junction
0.5 µm
1 µm
Desmosome
Gap junction
Extracellular
matrix
0.1 µm
Plasma membranes
of adjacent cells
Space
between
cells
Gap
junctions
Intermediate
filaments
Tight junctions prevent
fluid from moving
across a layer of cells
Figure 6.32 Intercellular junctions in animal tissues

76. Tight junction Desmosome Gap junction 0.5 µm 1 µm 0.1 µm
Figure 6.32 Intercellular junctions in animal tissues—tight junctions
Fig. 6-32b-d

77. The Cell: Living Unit Greater Than the Sum of Its Parts
Cells can’t function unless their structures & organelles work together
Ex. Macrophage must coordinate components such as the cytoskeleton, lysosomes, and plasma membrane to destroy bacteria.
Fig. 6-33
5 µm
An electron micrograph of a macrophage consuming bacteria
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78. The Endomembrane System: A Review (optional slide)
The endomembrane system is a complex and dynamic player in the cell’s compartmental organization
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings