Organization of the Cell

1
Organization of the Cell

• Chapter 4

2
Learning Objective 1

• What is cell theory?
• How does cell theory relate to the evolution of
  life?

3
Cell Theory

• Cells are basic units of organization and
  function in all living organisms
• All cells come from other cells
• All living cells have evolved from a common
  ancestor

4
Learning Objective 2

• What is the relationship between cell
  organization and homeostasis?

5
Homeostasis

• Cells have many organelles, internal structures
  that carry out specific functions, that help
  maintain homeostasis

6
KEY CONCEPTS

• Cell organization and size are critical in
  maintaining homeostasis

7
Plasma Membrane

• Plasma membrane
• surrounds the cell
• separates cell from external environment
• maintains internal conditions
• allows the cell to exchange materials with outer
  environment

8
KEY CONCEPTS

• Eukaryotic cells are divided into compartments by
  internal membranes
• Membranes provide separate, small areas for
  specialized activities

9
Learning Objective 3

• What is the relationship between cell size and
  homeostasis?

10
Biological Size
11

Mitochondrion
Red blood cells
Human egg
Chloroplast
Typical bacteria
Chicken egg
Protein
Virus
Amino acids
Nucleus
Atom
Smallest bacteria
Epithelial cell
Adult human
Ribosomes
Frog egg
Some nerve cells
1 µm
0.1 nm
1 nm
10 nm
100 nm
10 µm
10 m
1 m
100 mm
10 mm
1 mm
100 µm
Electron microscope
Light microscope
Human eye
Measurements 1 meter 1000 millimeters (mm) 1
millimeter 1000 micrometers (µm) 1 micrometer
1000 nanometers (nm)
Fig. 4-1, p. 75
12
Surface to Volume Ratio

• SVR
• ratio of plasma membrane (surface area) to cells
  volume
• regulates passage of materials into and out of
  the cell
• Critical factor in determining cell size

13
SVR
14

1 mm
2 mm
2 mm
1 mm
Surface area height width number of sides
number of cubes
48
24
Surface Area (mm2)
(1 1 6 8)
(2 2 6 1)
Volume height width length number of cubes
8
Volume (mm3)
8
(2 2 2 1)
(1 1 1 8)
Surface area/ volume
Surface Area/ Volume Ratio
3
6
(48 8)
(24 8)
Fig. 4-2, p. 76
15
Learning Objective 4

• What methods do biologists use to study cells?
• How are microscopy and cell fractionation used?

16
Microscopes

• Light microscopes
• Electron microscopes
• superior resolving power

17
Microscopes
18

Light microscope
Light beam
Ocular lens
Objective lens
Specimen
Condenser lens
Light source
(a) A phase contrast light microscope can be
used to view stained or living cells, but at
relatively low resolution.
100 µm
Fig. 4-4a, p. 79
19

Transmission electron microscope
Electron gun
Electron beam
First condenser lens (electromagnet)
Specimen
Projector lens (electromagnetic)
Film or screen
(b) The transmission electron microscope (TEM)
produces a high-resolution image that can be
greatly magnified. A small part of a thin slice
through the Paramecium is shown.
1 µm
Fig. 4-4b, p. 79
20

Scanning electron microscope
Electron gun
Electron beam
Second condenser lens
First condenser lens (electromagnet)
Scanning coil
Final (objective) lens
Cathode ray tube synchronized with scanning coil
Secondary electrons
Specimen
Electron detector
(c) The scanning electron microscope (SEM)
provides a clear view of surface features.
100 µm
Fig. 4-4c, p. 79
21
Cell Fractionation

• Cell fractionation
• purifies organelles
• to study function of cell structures

22
Cell Fractionation
23

Centrifuge rotor
Centrifugal force
Centrifugal force
Hinged bucket containing tube
(a) Centrifugation. Due to centrifugal force,
large or very dense particles move toward the
bottom of a tube and form a pellet.
Fig. 4-5a, p. 80
24

Layered microsomal suspension
Centrifuge supernatant 20,000 x G
Low sucrose concentration
Centrifuge supernatant 100,000 x G
Plasma membrane
Centrifuge 600 x G
Density gradient centrifugation
Resuspend pellet layer on top of sucrose gradient
90 minutes
10 minutes
30 minutes
100,000 x G
Sucrose density gradient
High
Golgi
sucrose concentration
Nuclei in pellet
Mitochondria, chloroplasts in pellet
Disrupt cells in buffered solution
Microsomal pellet (contains ER, Golgi, plasma
membrane)
ER
(b) Differential centrifugation. Cell structures
can be separated into various fractions by
spinning the suspension at increasing revolutions
per minute. Membranes and organelles from the
re-suspended pellets can then be further purified
by density gradient centrifugation (shown as last
step). G is the force of gravity. ER is the
endoplasmic reticulum.
Fig. 4-5b, p. 80
25

Stepped Art
Fig. 4-5b, p. 80
26
Learning Objective 5

• How do the general characteristics of prokaryotic
  and eukaryotic cells differ?
• How are plant and animal cells different?

27
Prokaryotes

• Prokaryotic cells
• No internal membrane organization
• nuclear area (not nucleus)
• cell wall
• ribosomes
• flagella

28
Prokaryotes
29

Pili
Storage granule
Flagellum
Ribosome
Cell wall
DNA
Plasma membrane
Nuclear area
Capsule
0.5 µm
Fig. 4-6, p. 81
30
Eukaryotes

• Eukaryotic cells
• membrane-enclosed nucleus
• cytoplasm contains organelles
• cytosol (fluid component)

31
Animal Cells
32

Chromatin
Membranous sacs of Golgi
Nuclear envelope
Nucleolus
Nuclear pores
Golgi complex
Nucleus
Plasma membrane
Lysosome
Nuclear envelope
Cristae
Ribosomes
Rough ER
Rough and smooth endoplastic reticulum (ER)
Centrioles
Mitochondrion
Smooth ER
Fig. 4-8, p. 83
33
Plant Cells

• Plant cells
• rigid cell walls
• plastids
• large vacuoles
• no centrioles

34
Plant Cells
35

Mitochondrion
Cristae
Membranous sacs
Golgi complex
Cell wall
Plasma membrane
Vacuole
Chloroplast
Nucleus
Granum
Smooth ER
Nuclear envelope
Stroma
Nucleolus
Nuclear pores
Rough ER
Chromatin
Ribosomes
Rough and smooth endoplasmic reticulum (ER)
Fig. 4-7, p. 82
36
Learning Objective 6

• What are the three functions of cell membranes?

37
Cell Membranes

• Divide cell into compartments
• Vesicles transport materials between compartments
• Important in energy storage and conversion
• Endomembrane system

38
Learning Objective 7

• What are the structures and functions of the
  nucleus?

39
The Nucleus

• Control center of cell
• genetic information coded in DNA
• Nuclear envelope
• double membrane
• Nuclear pores
• communicate with cytoplasm

40
Nuclear Structures

• Chromatin
• DNA and protein
• Chromosomes
• DNA condensed for cell division
• Nucleolus
• ribosomal RNA synthesis
• ribosome assembly

41
The Nucleus
42

Rough ER
Chromatin
Nuclear pores
Nucleolus
(b)
0.25 µm
Nuclear envelope
Nuclear pore
ER continuous with outer membrane of nuclear
envelope
Nucleoplasm
Outer nuclear envelope
Nuclear pore
2 µm
(a)
Nuclear pore proteins
Inner nuclear envelope
(c)
Fig. 4-11, p. 88
43
KEY CONCEPTS

• Eukaryotic cells have nuclei containing genetic
  information coded in DNA

44
Learning Objective 8

• What are the structural and functional
  differences between smooth ER and rough ER?

45
Endoplasmic Reticulum (ER)

• Network of folded membranes
• in cytosol
• Smooth ER
• lipid synthesis
• calcium ion storage
• detoxifying enzymes
• Rough ER
• ribosomes on outer surface
• assembles proteins

46
ER
47

ER lumen
Mitochondrion
Ribosomes
Rough ER
1 µm
Smooth ER
Fig. 4-12, p. 90
48
Learning Objective 9

• Trace the path of protein synthesis
• synthesis in the rough ER
• processing, modification, and sorting by the
  Golgi complex
• transportation to specific destinations

49
The Golgi Complex

• Processes proteins synthesized by ER
• Manufactures lysosomes
• Cisternae
• stacks of flattened membranous sacs

50
Transport Vesicles

• Formed by membrane budding
• Move glycoproteins
• from ER to cis face of Golgi complex
• Carry modified proteins from trans face to
  specific destination

51
Protein Synthesis
52

Polypeptides synthesized on ribosomes are
inserted into ER lumen.
Ribosomes
Sugars are added, forming glycoproteins.
Rough ER
Transport vesicles deliver glycoproteins to cis
face of Golgi.
Glycoprotein
cis face
Glycoproteins modified further in Golgi.
Glycoproteins move to trans face where they are
packaged in transport vesicles.
trans face
Glycoproteins transported to plasma membrane (or
other organelle).
Golgi complex
Contents of transport vesicle released from cell.
Plasma membrane
Fig. 4-14, p. 92
53
KEY CONCEPTS

• Proteins are
• synthesized on ribosomes
• processed in the endoplasmic reticulum
• processed by the Golgi complex
• transported by vesicles

54
Learning Objective 10

• What are the functions of lysosomes, vacuoles,
  and peroxisomes?

55
Other Organelles

• Lysosomes
• enzymes break down structures
• Vacuoles
• store materials in plant cells
• Peroxisomes
• produce and degrade hydrogen peroxide (catalase)

56
Learning Objective 11

• Compare the functions of mitochondria and
  chloroplasts
• How is ATP synthesized by each of these
  organelles?

57
Mitochondria

• Site of aerobic respiration
• Double membrane
• inner membrane folded (cristae)
• matrix (cristae and inner compartment)
• Important in apoptosis
• programmed cell death

58
Mitochondria
59

Outer mitochondrial membrane
Inner mitochondrial membrane
Matrix
Cristae
0.25 µm
Fig. 4-19, p. 95
60
Aerobic Respiration

• Breaks down nutrients using oxygen
• Energy from nutrients packaged in ATP
• CO2, H2O produced as by-products

61
Plastids

• Plastids
• organelles that produce and store food
• in cells of plants and algae
• Chloroplasts
• plastids that carry out photosynthesis

62
Chloroplast Structure

• Stroma
• fluid-filled space enclosed by inner membrane of
  chloroplast
• Grana
• stacks of membranous sacs (thylakoids)
• suspended in stroma

63
Chloroplasts
64

Inner membrane
Outer membrane
Stroma
1 µm
Granum (stack of thylakoids)
Intermembrane space
Thylakoid membrane
Thylakoid lumen
Fig. 4-20, p. 96
65
Photosynthesis

• Chlorophyll
• green pigment in thylakoid membranes
• traps light energy
• Light energy converted to chemical energy in ATP
• used to synthesize carbohydrates from carbon
  dioxide and water

66
Mitochondria and Chloroplasts
67

Photosynthesis Chloroplasts (some plant and algal
cells)
Aerobic respiration Mitochondria (most eukaryotic
cells)
Light
Glucose
Glucose
Fig. 4-18, p. 95
68
KEY CONCEPTS

• Mitochondria and chloroplasts convert energy from
  one form to another

69
Learning Objective 12

• What are the structures and functions of the
  cytoskeleton?

70
The Cytoskeleton

• Microtubules
• hollow tubulin cylinders
• MTOCs and MAPs
• Microfilaments
• actin filaments
• important in cell movement
• Intermediate filaments
• strengthen cytoskeleton
• stabilize cell shape

71
Microtubules
72

Dimer on
a-Tubulin
Plus end
ß-Tubulin
Minus end
Dimers off
(a) Microtubules are manufactured in the cell by
adding dimers of a-tubulin and ß-tubulin to an
end of the hollow cylinder. Notice that the
cylinder has polarity. The end shown at the top
of the figure is the fast-growing, or plus, end
the opposite end is the minus end. Each turn of
the spiral requires 13 dimers.
Fig. 4-22a, p. 98
73
Intermediate Filaments
74

Protofilament
Protein subunits
Intermediate filament
(a) Intermediate filaments are flexible rods
about 10 nm in diameter. Each intermediate
filament consists of components, called
protofilaments, composed of coiled protein
subunits.
Fig. 4-27a, p. 101
75

100 µm
(b) Intermediate filaments are stained green
in this human cell isolated from a tissue culture.
Fig. 4-27b, p. 101
76
Microfilaments
77

(a) A microfilament consists of two intertwined
strings of beadlike actin molecules.
Fig. 4-26a, p. 101
78

100 µm
(b) Many bundles of microfilaments (green) are
evident in this fluorescent LM of fibroblasts,
cells found in connective tissue.
Fig. 4-26b, p. 101
79
Cytoskeleton
80

Plasma membrane
Microfilament
Intermediate filament
Microtubule
Fig. 4-21, p. 97
81
Centrosome

• Main MTOC of animal cells
• Usually contains two centrioles
• Each centriole has 9 x 3 arrangement of
  microtubules

82
Centrioles
83

MTOC
Centrioles
0.25 µm
(a) In the TEM, the centrioles are positioned
at right angles to each other, near the nucleus
of a nondividing animal cell.
Fig. 4-24a, p. 99
84

(b) Note the 9 x 3 arrangement of
microtubules. The centriole on the right has been
cut transversely.
Fig. 4-24b, p. 99
85
A Kinesin Motor
86

Vesicle
Kinesin receptor
Kinesin
ATP
ATP
Plus end
Minus end
Microtubule does not move
Fig. 4-23, p. 98
87
KEY CONCEPTS

• The cytoskeleton is a dynamic internal framework
  that functions in various types of cell movement

88
Learning Objective 13

• How do cilia and flagella differ in structure and
  function?

89
Cilia and Flagella

• Cilia and flagella
• thin, movable structures
• project from cell surface
• function in movement
• Cilia are short, flagella are long

90
Cilia
91

0.5 µm
(a) TEM of a longitudinal section through cilia
and basal bodies of the freshwater protist
Paramecium multimicronucleatum. Some of the
interior microtubules are visible.
Fig. 4-25a, p. 100
92

0.5 µm
(b) TEM of cross sections through cilia showing 9
2 arrangement of microtubules.
Fig. 4-25b, p. 100
93

0.5 µm
(c) TEM of cross section through basal
body showing 9 x 3 structure.
Fig. 4-25c, p. 100
94

Outer pair of microtubules
Dynein
Plasma membrane
Central microtubules
(d) This 3-D representation shows nine attached
microtubule pairs (doublets) arranged in a
cylinder, with two unattached microtubules in the
center. The dynein arms, shown widely spaced
for clarity, are actually much closer
together along the longitudinal axis.
Fig. 4-25d, p. 100
95

(e) The dynein arms move the microtubules by
forming and breaking cross bridges on
the adjacent microtubules, so that one
microtubule walks along its neighbor. Flexible
linking proteins between microtubule pairs
prevent microtubules from sliding very far.
Instead, the motor action causes the microtubules
to bend, resulting in a beating motion.
Microtubular bend
Linking proteins
Dynein
Pair of microtubules
Fig. 4-25e, p. 100
96
Learning Objective14

• Describe the glycocalyx, extracellular matrix,
  and cell wall

97
Cell Coat

• Glycocalyx (cell coat)
• Surrounds cell
• Polysaccharides extend from plasma membrane

98
ECM

• Extracellular matrix (ECM)
• Surrounds many animal cell
• Carbohydrates and protein
• Fibronectins
• glycoproteins of ECM
• bind to integrins
• Integrins
• receptor proteins in plasma membrane

99
ECM
100

Collagen
Fibronectins
Extracellular matrix
Integrin
Intermediate filament
Plasma membrane
Microfilaments
Cytosol
Fig. 4-28, p. 102
101
Cell Wall

• Cellulose other polysaccharides
• form rigid cell walls
• in bacteria, fungi, and plant cells

102

Cell 1
Middle lamella
Primary cell wall
Multiple layers of secondary cell wall
Cell 2
2.5 µm
Fig. 4-29, p. 102
103
Typical Prokaryotic Cell
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Plant Cell Walls
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Cytoskeletal Components
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Common Eukaryotic Organelles
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Flagella Structure
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Motor Proteins
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The Endomembrane System
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