Cell Theory
• Every organism is composed of one
or more cells
• Cell is smallest unit with properties of
life
• Continuity of life arises from growth
and division of single cells
Cell
• Smallest unit of life
• Is highly organized for metabolism
• Senses and responds to environment
• Has potential to reproduce
The cell theory states that _____.
1.
2.
3.
4.
every organism consists of
one or more cells
the cell is the smallest unit
of organization that
displays all the properties
of life
the continuity of life arises
directly from the growth
and division of single cells
all of the choices
0%
1
0%
2
0%
3
0%
4
Structure of Cells
All start out life with:
– Plasma membrane
– Region where DNA
is stored
– Cytoplasm
Two types:
– Prokaryotic
– Eukaryotic
Types of Cells
cytoplasm
DNA in
nucleoid
Bacterial cell
(prokaryotic)
plasma membrane
Fig. 3-1a, p.39
The DNA of a prokaryotic cell is located in the _____.
1.
2.
3.
4.
nucleus
plasma membrane
nucleoid
cell wall
0%
1
0%
2
0%
3
0%
4
Plant cell
(eukaryotic)
Types of Cells
DNA in nucleus
cytoplasm
plasma membrane
Fig. 3-1b, p.39
Most Cells Are Really Small
Fig. 3-4, p.41
Microscopes
• Create detailed images of something
that is too small to see
• Light microscopes
– Simple or compound
• Electron microscopes
– Transmission EM or Scanning EM
Limitations of Light
Microscopy
• Cells must be thin enough for light to
pass through
• Structures are usually stained
• Light microscopes can see details 200
nm in size
Microscopes
Fig. 3-2a, p.40
Path of light rays
(bottom to top) to eye
Ocular lens enlarges
primary image formed
by objective lenses.
Prism
(directs rays to
ocular lens)
Objective lenses (closest
to specimen) form
primary image.
Stage (holds
microscope slide in
position)
Condenser lenses focus
light rays through specimen.
Illuminator
Fig. 3-2a, p.40
Electron Microscopy
• Uses beams of electrons rather than
light
• Electrons are focused by magnets
rather than glass lenses
• Can resolve structures down to 0.5 nm
Different Views
Structure of Cell Membranes
• Fluid mosaic model
• Mixed composition:
– Phospholipid bilayer
– Glycolipids
– Sterols
– Proteins
Prokaryotic Cells
• Archaebacteria and eubacteria
• DNA is not enclosed in nucleus
• Generally the smallest, simplest cells
Fig. 3-8b, p.44
The DNA of a typical prokaryote is organized into _____.
1. a single circular
chromosome
2. many rod-shaped
chromosomes
3. a corkscrew shaped
chromosome
4. a spherical jellylike
mass in the nucleoid
region
0%
1
0%
2
0%
3
0%
4
Eukaryotic Cells
• Have a nucleus and other
organelles
• Eukaryotic organisms
– Plants
– Animals
– Protistans
– Fungi
Eukaryotic Cell Features
• Plasma membrane
• Nucleus
• Endoplasmic
reticulum
• Golgi body
• Vesicles
• Mitochondria
• Ribosomes
• Cytoskeleton
ribosome
vesicle
rough ER
The Nucleus
Fig. 3-9b-c, p.46
Endoplasmic Reticulum
• Starts at nuclear membrane and
extends throughout cytoplasm
• Rough ER: ribosome covered,
processes proteins
• Smooth ER: no ribosomes, builds lipids
Secretory pathway ends.
Endocytic pathway begins.
budding vesicle
plasma membrane
Golgi body
Golgi Body
Fig. 3-9e-f, p.46
Vesicles
• Membranous sacs that
move through cytoplasm
• Lysosomes
• Peroxisomes
Cogito ergo….
1. sum
2. non sum
0%
no
n
su
su
m
m
0%
Mitochondria
• ATP-producing powerhouses
• Membranes form two distinct
compartments
• ATP-making machinery embedded
in inner mitochondrial membrane
outer membrane
outer compartment
inner compartment
inner membrane
Fig. 3-10, p.48
FOOD
fats
fatty
acids
glycerol
glycogen
complex
carbohydrates
proteins
simple sugars
amino acids
glucose-6-phosphate
NH3
GLYCOLYSIS
PGAL
pyruvate
acetyl-CoA
KREBS
CYCLE
urea
carbon
backbones
Krebs cycle
The
Nucleus
nucleolus
chromatin
nuclear envelope
(two lipid bilayers)
Fig. 3-9a, p.46
glucose
Figure 6.5
Page 87
NAD+
2 ATP
4 ATP
2 PGAL
2 NADH
2 pyruvate
2 CO2
2 NADH2
2 acetyl-CoA
2 NADH
H+
H+
2 ATP
6 NADH
Krebs
cycle
H+
ATP
2 FADH2
4 CO2
H+
ATP
36 ATP
H+
H+
ADP
electron
+Pi
transfer
phosphorylation
H+
H+
H+
The function of a mitochondrion is to _____.
1. produce protein
2. make ATP
3. attach sugar side
chains to some
proteins and lipids
4. degrade toxins
0%
1
0%
2
0%
3
0%
4
Chloroplasts
• Convert sunlight energy to ATP through
photosynthesis
• Found in plants and some protistans
two outer
membranes
thylakoids
(inner membrane
system folded into
flattened disks)
Fig. 3-11, p.48
Griffith Discovers
Transformation
• 1928
• Attempting to develop a vaccine
• Isolated two strains of Streptococcus
pneumoniae
– Rough strain was harmless
– Smooth strain was pathogenic
Griffith Discovers
Transformation
1. Mice injected with
live cells of harmless
strain R
2. Mice injected with live
cells of killer strain S
3. Mice injected with
heat-killed S cells
4. Mice injected with
live R cells plus heatkilled S cells
Mice live. No live R
cells in their blood
Mice die. Live S cells in
their blood
Mice live. No live S cells
in their blood
Mice die. Live S cells in
their blood
Transformation
• Harmless R cells were transformed by
material from dead S cells
• Descendents of transformed cells were
also pathogenic
What Is the
Transforming Material?
• Avery found protein-digesting enzymes
did not change results
– extracts still transformed bacteria
• But treated with DNA-digesting
enzymes
– extracts lost transforming ability
• Concluded that DNA, not protein,
transforms bacteria
If DNA from a disease-causing bacterium is
added to the nucleus of a bacterium that
normally does not cause disease, _____.
73%
1.
the new bacterium
will cause the
disease
2.
the new bacterium
will not cause the
disease
3.
the bacterium will die
4.
the bacterium will be
resistant to the
disease
12%
7%
1
2
3
8%
4
Bacteriophages
• Viruses that infect
bacteria
• Consist of protein
and DNA
• Inject their
hereditary material
into bacteria
Bacteriophages
Bacteriophages are _____.
1. bacteria that infect
viruses
93%
2. bacteria that infect
humans
3. viruses that infect
bacteria
4. viruses that infect
humans
6%
1
1%
2
0%
3
4
Hershey and Chase’s
Experiments
• Created labeled bacteriophages
– Radioactive sulfur
– Radioactive phosphorus
• Allowed labeled viruses to infect bacteria
• Where were the radioactive labels after
infection?
35S
remains
outside cells
virus particle
labeled with 35S
DNA (blue)
being injected
into bacterium
virus particle
labeled with 32P
35P
remains
inside cells
DNA (blue)
being injected
into bacterium
Fig. 9-2, p.139
Hershey and Chase Results
35S
remains
outside cells
32P
remains
inside cells
2nm diameter overall
Structure of
DNA
In 1953,
Watson and
Crick showed
that DNA is a
double helix
0.34 nm between
each pair of bases
3.4 nm length of each
full twist of helix
Watson and Crick
Watson-Crick Model
• DNA molecule is a double helix
• Consists of two nucleotide strands that
run in opposite directions
• Strands are held together by hydrogen
bonds between bases
• A binds with T, C binds with G
Structure of Nucleotides
in DNA
• Each nucleotide consists of
– Deoxyribose (5-carbon sugar)
– Phosphate group
– A nitrogen-containing base
• There are four bases:
– Adenine, Guanine, Thymine, Cytosine
Nucleotide Bases
ADENINE
(A)
phosphate
group
GUANINE
(G)
deoxyribose
THYMINE
(T)
CYTOSINE
(C)
Composition of DNA
• Amount of adenine relative to guanine
differs among species
• Amount of adenine always equals
amount of thymine, and amount of
guanine always equals amount of
cytosine
A=T and G=C
Rosalind Franklin’s
Work
• Expert in x-ray
crystallography
• Used technique to
examine DNA fibers
Concluded that DNA
was some sort of helix
The double-helix structure of the DNA
molecule was discovered by _____.
1. Watson and
Crick
58%
2. Wilkins
34%
3. Franklin
4. all of the choices
7%
0%
1
2
3
4
DNA Structure
Allows It to Duplicate
• Two nucleotide strands held together by
hydrogen bonds
• Hydrogen bonds between two strands
are easily broken
• Each single strand serves as template
for new strand
2-nanometer diameter overall
DNA
Models
0.34-nanometer distance
between each pair of bases
3.4-nanometer length of
each full twist of the double helix
In all respects shown here, the
Watson–Crick model for DNA
structure is consistent with the
known biochemical and x-ray
diffraction data.
The pattern of base pairing (A
only with T, and G only with C)
is consistent with the known
composition of DNA (A = T, and
G = C).
Fig. 9-6, p.141
In 1952, Franklin reported that the DNA
molecule was a double helix with a
backbone formed of _____.
62%
1. phosphate
groups
2. purines
3. pyrimidines
10%
4. nitrogencontaining bases
1
2
12%
3
16%
4
Patterns of Base Pairing
• A to T
• G to C
one
base
pair
or
or
DNA
Replication
• Each parent
strand remains
intact
• Every DNA
molecule is half
“old” and half
“new”
new
old
old
new
Base Pairing
during
Replication
Each old strand is
template for new
complementary
strand
Which of the following is a correct pairing of
nitrogen-containing bases in DNA?
90%
1. A = T
2. T = G
3. C = A
4. G = A
4%
1
2
3%
3
3%
4
Enzymes in Replication
• Enzymes unwind the two strands and
complementary base pairs unzip
• DNA polymerase attaches new
complementary nucleotides
• DNA ligase fills in gaps
• Enzymes wind two strands together
DNA Repair
• Mistakes can occur during replication
• DNA polymerase reads correct
sequence from complementary strand
and, together with DNA ligase, repairs
mistakes in incorrect strand
In DNA replication, a permanent alteration in
the DNA sequence is called a _____.
84%
1. genetic code
2. mutation
3. proofreading
error
4. semiconservativ
e replication
9%
1
5%
2
3
2%
4
Which of the following
statements about DNA is true?
1.
changes in DNA can
be inherited by future
generations
2.
the term DNA stands
for deoxyribonucleic
acid
3.
DNA codes all
information needed to
produce a human
being
4.
all of the choices
97%
0%
1
2%
2
2%
3
4
DNA Sequencing
• Order of
fluorescent
bands indicates
DNA sequence
DNA Fingerprints
• Unique array of DNA fragments
• Inherited from parents in Mendelian
fashion
• Even full siblings can be distinguished
from one another by this technique
Analyzing DNA Fingerprints
• DNA is separated by gel electrophoresis
• Pattern of bands is used to
– Identify or rule out criminal suspects
– Identify bodies
– Determine paternity
A DNA Fingerprint
Clones
Cloning
• Making a genetically identical copy of
an individual
• Researchers have been creating clones
for decades
• Clones can be created by embryo
splitting (artificial twinning)
Clones from Adult Cells
• In nucleus of differentiated cells, most
DNA is turned off
• Some DNA is turned on when nucleus
is transferred to egg cell
• New organism is genetically identical to
donor of nucleus
Nuclear
Transfer
• Nucleus of egg
replaced with
nucleus of adult
cell
More Clones
• Numerous species been cloned
Mice, pigs, cattle, cats, etc.
• Most cloning attempts are still
unsuccessful
• Many clones have defects
• Clones may vary in their phenotype
More Clones
Stem Cells
• Embryonic
• Adult
Embryonic Cells
I’m familiar with the arguments
about stem cell research.
50%
50%
se
Fa
l
Tr
ue
1. True
2. False
Stem cell research is
morally/ethically objectionable
50%
50%
ee
gr
Id
isa
Ia
gr
ee
1. I agree
2. I disagree