1. Essentials of
Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 4
Inside the Cell
Lecture Outline
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
See separate FlexArt PowerPoint slides for
all figures and tables pre-inserted into
PowerPoint without notes.

2. 4.1 Cells Under the Microscope
• Cells
 Are extremely diverse
 Nearly all require a microscope to be seen
 Each type in our body is specialized for a
particular function
• Light microscope
 Invented in 17th
century
 Limited by properties of light
• Electron microscope
 Invented in 1930s
 Overcomes limitation by using beam of
electrons

3. Figure 4.1 Using microscopes to see cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
LM of Euglena
SEM of spiderling
Scientist using a light microscope.
Scientist using
an electron
microscope.
TEM of human lymphocyte
(TEM, lymphocyte): © Dr. Gopal Murti/Visuals Unlimited; (electron microscope): © Inga Spence/Visuals Unlimited; (light microscope): © Corbis Images/Jupiter Images RF;
(Euglena): © Tom Adams/Visuals Unlimited; (SEM, spider): © Science Photo Library.Getty RF

4. Figure 4.2 Relative sizes of some living things and their components
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
unaided eye
electron microscope
1 km100 m10 m1 m0.1 m1 cm1 mm100 nm10 nm1 nm0.1 nm
mouse
most bacteria
viruses
proteins
amino acids
atom
s
ant
human
blue whale
chloroplast
light microscope
plant and
animal
cells
human
egg
frog
egg
1 µm 10 µm 100 µm

5. • Why are cells so small?
 Need surface areas large enough for entry
and exit of materials
 Surface-area-to-volume ratio
 Small cells have more surface area for
exchange
 Adaptations to increase surface area
• Microvilli in the small intestine increase
surface area for absorption of nutrients

6. 4.2 The Two Main Types of Cells
• Cell theory
 All organisms are composed of cells
 All cells come only from preexisting cells
• All cells have a plasma membrane
 Encloses cytoplasm and genetic material
• 2 main types of cells
 Based on organization of genetic material
1. Prokaryotic cells – lack membrane-bounded
nucleus
2. Eukaryotic cells – have nucleus housing DNA

7. Figure 4.3 Comparison of prokaryotic cells and eukaryotic cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Prokaryotic cell: simple
internal structure
Eukaryotic cell: complex
internal structure
cell
flagella

8. • Prokaryotic cells
 Organisms from the domains Bacteria and
Archaea
 Generally smaller and simpler in structure
than eukaryotic cells
• Allows them to reproduce very quickly and
effectively
 Extremely successful group of organisms
 Bacteria
• Well known because some cause disease
• Others have roles in the environment
• Some are used to manufacture chemicals,
food, drugs, etc.

9. • Bacterial structure
 Cytoplasm surrounded by plasma membrane and
cell wall
• Sometimes a capsule – protective layer
• Plasma membrane is the same as eukaryotes
 Cell wall maintains the shape of a cell
 DNA – single coiled chromosome located in
nucleoid (region – not membrane enclosed)
 Ribosomes – site of protein synthesis
 Appendages
• Flagella – propulsion
• Fimbriae – attachment to surfaces
• Conjugation pili – DNA transfer

10. Figure 4.4 Prokaryotic cell
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(right); © Ralph A. Slepecky/Visuals Unlimited
fimbriae
hair like bristles
that allow
adhesion
to surfaces
conjugation pilus
elongated, hollow
appendage used to transfer
DNA to other cells
capsule
gel-like coating outside
the cell wall
nucleoid
location of the bacterial
chromosome
ribosome
site of protein synthesis
flagellum
rotating filament that
propels the cell
cytoplasm
semifluid solution surrounded
by the plasma membrane;
contains nucleoid and
ribosomes
plasma membrane
sheet that surrounds the
cytoplasm and regulates
entrance and exit of molecules
cell wall
structure that provides support
and shapes the cell

11. 4.3 The Plasma Membrane
• Marks boundary between outside and
inside of a cell
• Regulates passage in and out of a cell
• Phospholipid bilayer with embedded
proteins
 Polar heads of phospholipids face into
watery medium
 Nonpolar tails face each other
• Fluid-mosaic model – pattern that
varies

12. Figure 4.5 A model of the plasma membrane
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
carbohydrate chain
glycoprotein
cholesterol
hydrophobic
phospholipid
hydrophilic
hydrophilic
polar head
nonpolar tail Outside of cell
Inside of cell
external membrane
surface
cytoskeleton
filaments
protein molecule
phospholipid
bilayer
internal membrane
surface

13. • Membrane
proteins
 Channel
proteins
• Form tunnel for
specific
molecules
Figure 4.6a Membrane protein
diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Channel protein

14. Transport proteins
•Involved in passage
of molecules through
the membrane,
sometimes requiring
input of energy
Figure 4.6b Membrane
protein diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b. Transport protein

15. Cell recognition
proteins
•Enable our body
to distinguish
between our own
cells and cells of
other organisms
Figure 4.6c Membrane
protein diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
c. Cell recognition protein

16.  Receptor proteins
• Allow signal
molecules to
bind, causing a
cellular response
Figure 4.6d Membrane
protein diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
d. Receptor protein

17. Enzymatic
proteins
•Directly participate
in metabolic
reactions
Figure 4.6e Membrane protein
diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
e. Enzymatic protein

18. Junction
proteins
•Form junctions
between cells
•Cell-to-cell
adhesion and
communication
Figure 4.6f Membrane protein
diversity
f. Junction proteins
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. 4.4 Eukaryotic cells
• Protists, fungi, plants, and animals
• Have a membrane-bounded nucleus
housing DNA
• Much larger than prokaryotic cells
• Compartmentalized and contain organelles
• 4 categories of organelles:
1. Nucleus and ribosomes
2. Endomembrane system
3. Energy-related
4. Cytoskeleton

20. Figure 4.7 Structure of typical animal cell
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a); © Dr. Dennis Kunkel/Visuals Unlimited
microtubules
chromatin
nucleolus
a.
×10,000
vesicle
rough ER
Golgi apparatus
plasma membrane
cytoplasm
chromatin
nucleolus
nucleus:
smooth ER
lysosome
mitochondrion
b.
vesicle
formation
centrioles
(in centrosome)
ribosome
(attached to rough ER)
ribosome
(in cytoplasm)
polyribosome
(in cytoplasm)
cytoskeleton:
nuclear
pore
plasma
membrane
nuclear
envelope
endoplasmic
reticulum
nuclear
envelope
filaments

21. Figure 4.8 Structure of a typical plant cell
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mitochondrion
chloroplast
central vacuole
rough ER
smooth ERcell wall
plasma membrane
Golgi apparatus
cytoplasm
cell wall of adjacent cell
cytoskeleton:
filaments
microtubule
chromatin
nucleolus
nucleus:centrosome
mitochondrion
nucleus
chloroplast
a. × 7,700
cell wall
central
vacuole
ribosome
(in cytoplasm)
ribosome
(attached to
rough ER)
nuclear
envelope
nuclear
pore
plasma
membrane
b.
(a): © Newcomb/Wergin/Biological Photo Service

22. 1. Nucleus and ribosomes
 Nucleus
• Stores genetic information
• Chromatin – diffuse DNA, protein, some RNA
 Prior to cell division, DNA compacts into
chromosomes
• DNA organized into genes which specify a
polypeptide
 Relayed to ribosome using messenger RNA
(mRNA)
• Nucleolus – region where ribosomal RNA
(rRNA) is made
• Nuclear envelope – double membrane
 Nuclear pores permit passage in and out

23. Figure 4.9 Structure of the nucleus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
nuclear pores
SEM of
freeze-fractured
nuclear envelope
ER lumen
nucleoplasm
chromatin
nucleolus
nuclear envelope
outer membrane
inner membrane
(right): Courtesy E.G. Pollock
endoplasmic reticulum
ribosome

24.  Ribosomes
• Carry out protein synthesis in the cytoplasm
• Found in both prokaryotes and eukaryotes
• Composed of 2 subunits
• Mix of proteins and ribosomal RNA (rRNA)
• Receive mRNA as instructions sequence of
amino acids in a polypeptide
• In eukaryotes,
 Some ribosomes free in cytoplasm
 Many attached to endoplasmic reticulum

25. Figure 4.10 The nucleus, ribosomes, and endoplasmic reticulum
(ER)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
receptor
ribosome
Cytoplasm
nuclear pore
ribosome
Nucleus
ribosome
ER membrane
Endoplasmic reticulum
large subunit
1
2 3
4
DNA
mRNA
mRNA is produced in
the nucleus but moves
through a nuclear pore
into the cytoplasm.
In the cytoplasm, the
mRNA and ribosomal
subunits join, and
polypeptide synthesis
begins.
lumen of
the ER
If a ribosome attaches
to a receptor on the ER,
the polypeptide enters
the lumen of the ER.
At termination, the polypeptide
becomes a protein. The
ribosomal subunits disengage,
and the mRNA is released.
polypeptide
protein
small
subunit

26. 1. Endomembrane system
 Consists of nuclear envelope,
membranes of endoplasmic reticulum,
Golgi apparatus, and vesicles
 Helps compartmentalize cell
• Restricts certain reactions to specific regions
 Transport vesicles carry molecules from
one part of the system to another

27. • Endoplasmic reticulum
 Complicated system of membranous channels and
saccules
 Physically continuous with outer membrane of
nuclear envelope
 Rough ER
• Studded with ribosomes
• Modifies proteins in lumen
• Forms transport vesicles going to Golgi apparatus
 Smooth ER
• Continuous with rough ER
• No ribosomes
• Function depends on cell
 Produces testosterone, detoxifies drugs

28. Figure 4.11 Endoplasmic reticulum (ER)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
rough ER
ribosomes
smooth ER
nuclear envelope
© R. Bolender and D. Fawcett/Visuals Unlimited

29. • Golgi apparatus
 Stack of flattened saccules
 Transfer station
 Receives vesicles from ER
 Modifies molecules
 Sorts and repackages for new destination
• Some are lysosomes
• Lysosomes
 Vesicles that digest molecules or portions
of the cell
 Digestive enzymes
 Tay-Sachs disease

30. Figure 4.12 Endomembrane system
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
smooth ER
synthesizes lipids and
performs other functions.
transport vesicles
from smooth ER
lysosomes
digest molecules
or old cell parts.
incoming vesicles
bring substances into
the cell.
secretory vesicles
fuses with the plasma
membrane as secretion
occurs.
Golgi apparatus
modifies lipids and
proteins; sorts them and
packages them in
vesicles.
transport vesicles
from rough ER
rough ER
synthesizes proteins
and packages them in

31. • Vacuoles
 Membranous sacs
 Larger than vesicles
 Rid a cell of excess water
 Digestion
 Storage
• Plant pigments
• Animal adipocytes

32. Figure 4.13 Vacuoles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
b.
c.
×7,700
×400
vacuoles
80 0
a: © Roland/Birke/Peter Arnold/Photolibrary; b: © Newcomb/Wergin/Biological Photo Service; c: © The McGraw Hill Companies, Inc./Al Telser, photographer

33. 1. Energy-related organelles
 Chloroplasts
• Use solar energy to synthesize carbohydrates
• Only in plants
• Three-membrane system
 Double membrane enclosing stroma
• Thylakoids formed from third membrane
 Thylakoid membrane contains pigments that
capture solar energy
• Endosymbiosis – origin of chloroplasts
 Chloroplasts have their own DNA and ribosomes

34. Figure 4.14a Chloroplast structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Dr. George Chapman/Visuals Unlimited
stroma
granum
×35,000
a.

35. Figure 4.14b Chloroplast structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
thylakoid
stroma
granum
outer membrane
inner membrane
b.
double
membrane
thylakoid
membrane
thylakoid
space

36.  Mitochondria
• Break down carbohydrates to produce adenosine
triphosphate (ATP)
• Found in BOTH plants and animals
• Usually only visible under an electron microscope
• Bounded by double membrane
• Inner membrane folds called cristae
 Increase surface area
• Inner membrane encloses matrix
 Mixture of enzymes assisting in carbohydrate breakdown
 Reactions permit ATP synthesis
• Cellular respiration – needs oxygen, produces carbon
dioxide
• Endosymbiosis – also contains its own DNA and
ribosomes

37. Figure 4.15 Mitochondrion structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cristae
b.
×70,000
a.
outer membrane
inner membrane
matrix
double
membrane
b: Courtesy Keith Porter

38. 1. Cytoskeleton
 Network of interconnected protein
filaments and tubules
 Extends from the nucleus to the plasma
membrane
 Only in eukaryotes
 Maintains cell shape
 With motor proteins, allows cell and
organelles to move

39. • Microtubules
 Small, hollow cylinders
 Assembly controlled by centrosome
 Help maintain cell shape and act as
trackways
• Intermediate filaments
 Intermediate in size
 Ropelike assembly
 Run from nuclear envelope to plasma
membrane

40. Figure 4.16 Microtubules
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
microtubule
centrosome
nucleus
cell

41. •Actin filaments
2 chains of monomers twisted in a helix
Forms a dense web to support the cell

42. Figure 4.17 Actin filaments
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
microvilli
nucleus
cell
actin
filaments

43. • Motor proteins
 Instrumental in allowing cellular movements
 Myosin
• Interacts with actin
• Cells move in amoeboid fashion
• Muscle contraction
 Kinesin and dynein
• Move along microtubules
• Transport vesicles from Golgi apparatus to final
destination

44. Figure 4.18b Motor proteins
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
microtubule
kinesin
b. Kinesin
kinesin
receptor
vesicle moves,
not microtubule
ATP
vesicle

45. • Centrioles
 Made of 9 sets of microtubule triplets
 Two centrioles lie at right angles
 In animal cells, not present in plant cells

46. Figure 4.19 Centrioles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
one microtubule
triplet
one pair of centrioles in a
centrosome
(Left); © Don W. Fawcett/Photo Researchers, Inc

47. • Cilia and flagella
 Eukaryotes
 For movement of the cell or fluids past the
cell
 Similar construction in both
• 9+2 pattern of microtubules
 Cilia shorter and more numerous than
flagella

48. Figure 4.20 Cilia and
flagella
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b.
Flagellum
triplets
Basal body
dynein side arms
TEM ×101,000
TEM ×350,000
Basal body
cross section
plasma
membrane
central
microtubules
microtubule
doublet
Flagellum
cross section
a.
cilia in bronchial wall of lungs flagella of sperm
a; (cilia): © Manfred Kage/Peter Arnold/Photolibrary; a(sperm): © David M. Phillips/Photo Researchers, Inc.;
b (both): © William L. Dentler/Biological Photo Service

49. 4.5 Outside the Eukaryotic Cell
• Plant cell walls
 Primary cell walls
• Cellulose fibrils and noncellulose substances
• Wall stretches when cell is growing
 Secondary cell walls
• Forms inside primary cell wall
• Woody plants
• Lignin adds strength
 Plasmodesmata
• Plant cells connected by numerous channels that pass
through cell walls
• For exchange of water and small solutes between cells

50. Figure 4.21 Plasmodesmata
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cell wall
plasmodesmata
cell wall
Cell 1 Cell 2
cell wall
cytoplasm cytoplasm
middle lamella
plasmodesmata
×53,000
plasma
membrane
(Bottom): © E.H. Newcomb/Biological Photo Service

51. • Exterior cell surfaces in animals
 No cell wall
 Extracellular matrix (ECM)
• Meshwork of fibrous proteins and
polysaccharides
• Collagen and elastin well-known proteins
• Matrix varies – flexible in cartilage, hard in bone

52. Figure 4.22 Animal cell extracellular matrix
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
collagen
polysaccharide
cytoplasm
elastic fiber
receptor
protein
cytoskeleton
filament

53. • Junctions between cells
 Adhesion junctions
• Internal cytoplasmic plaques joined by
intercellular filaments
• Sturdy but flexible sheet of cells

54. Figure 4.23a Junctions between cells of the intestinal wall
(Left); From Douglas E. Kelly, Journal of Cell Biology, 28 (1966:51). Reproduced by permission of The Rockefeller University Press
Adhesion junction
plasma
membranes
filaments of
cytoskeleton
intercellular
space
intercellular
filaments
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

55. Tight junctions
•Plasma membrane
proteins attach to each
other
•Zipper-like
•Cells of tissues that
serve as barriers
Figure 4.23b Junctions between
cells of the intestinal wall
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
intercellular space
plasma
membranes
tight junction
proteins
Tight junction

56. Gap junctions
•Allow cells to
communicate through
plasma membrane
channels
•Lend strength while
allowing small
molecules and ions to
pass through
Figure 4.23c Junctions between cells of
the intestinal wall
Gap junction
plasma
membranes
membrane
channel
intercellular
space
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.