AP Biology
The Cell Cycle
Part 1
One cell becoming two
Binary Fission in
Prokaryotes
Cell wall
Origin of
replication
E. coli cell
Chromosome replication
begins.
Soon thereafter,
one copy of the origin
moves rapidly toward the
other end of the cell.
Replication continues. One
copy of the origin is now at
each end of the cell.
Replication finishes.
The plasma membrane
grows inward, and
new cell wall is deposited.
Two daughter
cells result.
Two copies
of origin
Origin
Plasma
membrane
Bacterial
chromosome
Origin
Chromatin vs. Chromosomes
appearance within the cell.
Coiling up of Chromatin
using histones
Somatic cells vs. Germ cells
The egg surrounded by sperm.
Sister Chromatids
Mitosis (1 Division) vs.
Meiosis (2 Divisions)
AP Biology
The Cell Cycle
Part 2
Centrioles
Interphase
Before and after the S phase
Interphase cell
(Look at the chromatin in the blue nucleus and the
yellow cytoskeleton.)
Start of Mitosis
Cell in Prophase
Mitosis
“Division of the nucleus”
Cell in Metaphase
Cell in Anaphase
Cell in Telophase and starting
Cytokinesis
One cell becoming two
Motor Protein and the
Spindle Fibers
Chromosome
movement
Microtubule
Motor
protein
Chromosome
Kinetochore
Tubulin
subunits
Animal vs. Plant
LE 12-10
Nucleus
Nucleolus
Chromatin
condensing
Prophase. The
chromatin is condensing.
The nucleolus is beginning to
disappear.
Although not yet visible in
the micrograph, the mitotic
spindle is starting to form.
Chromosomes
Prometaphase. We
now see discrete chromosomes;
each
consists of two identical sister
chromatids. Later
in prometaphase, the
nuclear envelope will fragment.
Cell plate
Metaphase. The spindle is
complete, and the
chromosomes, attached to
microtubules at their
kinetochores, are all at
the metaphase plate.
Anaphase. The
chromatids of each
chromosome have
separated, and the daughter
chromosomes are moving to
the ends of the cell as their
kinetochore microtubules shorten.
10 µm
Telophase. Daughter nuclei
are forming. Meanwhile,
cytokinesis has started: The
cell plate, which will divide
the cytoplasm in two, is
growing toward the
perimeter of the parent
cell.
Microscopic view of Mitosis in Onion root tips.
Can you identify the stages?
Checkpoints
(Is all going according to plan?)
AP Biology
Chapter 12:
The Cell Cycle
Checkpoints
(Is all going according to plan?)
.
M
G1
S
G2
M
G1
S
G2
M
MPF activity
Cyclin
Time
Fluctuation of MPF activity and cyclin concentration
during the cell cycle
.
Cdk
Degraded
cyclin
G2
checkpoint
Cyclin is
degraded
MPF
Cdk
Cyclin
Molecular mechanisms that help regulate the cell cycle
.
Chromosome
movement
Microtubule
Motor
protein
Chromosome
Kinetochore
Tubulin
subunits
.
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete
single layer, they stop dividing
(density-dependent inhibition).
If some cells are scraped away, the
remaining cells divide to fill the gap and
then stop (density-dependent inhibition).
Normal mammalian cells
25 µm
.
Cancer cells do not exhibit
anchorage dependence
or density-dependent inhibition.
25 µm
Cancer cells
Malignant cancer cells from the breast
(See the ABNORMAL “crab” shape of the cells.)
Mutations and Cancer
MUTATION
Growth
factor
Hyperactive
Ras protein
(product of
oncogene)
issues signals
on its own
G protein
Cell cycle-stimulating
pathway
Receptor
Protein kinases
(phosphorylation
cascade)
NUCLEUS
Transcription
factor (activator)
DNA
Gene expression
Protein that
stimulates
the cell cycle
Cell cycle-inhibiting
pathway
Protein kinases
MUTATION
UV
light
DNA damage
in genome
Active
form
of p53
DNA
Protein that
inhibits
the cell cycle
Defective or
missing
transcription
factor, such as
p53, cannot
activate
transcription
AP Biology
Cell Communication (Signaling)
Part 1
Direct Contact
Local and Long Distance within an
organism.
Phermones
Earl Sutherland
Step 1: Reception
Step 2: Transduction
Step 3: Response
See the
CONFORMATION
SHAPE CHANGE by the
receptor protein
caused by the ligand
binding.
Signal
molecule
(ligand)
Gate
closed
Ligand-gated
ion channel receptor
Ions
Plasma
membrane
Gate open
Cellular
response
Gate closed
AP Biology
Cell Communication (Signaling)
Part 2
Phosphorylation and Hydrolysis
Receptor Protein
G protein Receptor
Tyrosine – Kinase Receptor
Ion Channel Receptors
Signal
molecule
(ligand)
Gate
closed
Ligand-gated
ion channel receptor
Ions
Plasma
membrane
Gate open
Cellular
response
Gate closed
Intracellular receptors
Secondary Messenger
cAMP
Adenylyl cyclase
Phosphodiesterase
Pyrophosphate
H2O
P
ATP
Pi
Cyclic AMP
AMP
First messenger
(signal molecule
such as epinephrine)
Adenylyl
cyclase
G protein
G-protein-linked
receptor
GTP
ATP
cAMP
Second
messenger
Protein
kinase A
Cellular responses
Secondary Messenger Calmodulin
EXTRACELLULAR
FLUID
Signal molecule
(first messenger)
G protein
DAG
GTP
G-protein-linked
receptor
Phospholipase C
PIP2
IP3 (second
messenger)
IP3-gated
calcium channel
Endoplasmic
reticulum (ER)
CYTOSOL
Ca2+
Ca2+
(second
messenger)
Various
proteins
activated
Cellular
responses
AP Biology
Cell Communication (Signaling)
Part 3
Kinases “turn on” processes
Phosphotases “turn off” processes
Small signal produces a BIG response
The Big picture
Growth factor
Reception
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription
factor
Active
transcription
factor
P
Response
DNA
Gene
NUCLEUS
mRNA
Scaffolding Proteins
Signal
molecule
Plasma
membrane
Receptor
Three
different
protein
kinases
Scaffolding
protein
Tyrosine – Kinase Receptor
(Evolution – Change over TIME)