Transcript The Cell Cycle and Mitosis

Wednesday, December 14th, 1:30- 3:00 PM
Cell Growth
Cell cycle and Mitosis
Why are cells small?
Surface area to volume ratio
As a cell grows bigger, its internal
volume enlarges and the cell
membrane expands.
The volume increases more
rapidly than does the surface area
this causes a problem.
Cell size and material exchange

The larger a cell
grows the more
trouble it has…

moving enough
nutrients in

Moving all the
waste materials
out
DNA Overload
Checkpoint!!!!

What are two problems that cell growth
causes for cells?


The larger a cell becomes, the more demands
the cell places on its _____ and the more trouble
the cell has moving enough _________and
_________ across the cell membrane.
What is viable solution for cells solve these
problems?

Cell Division – A larger cell splits into two smaller
daughter cells.
The Cell Cycle and Mitosis
Make diagram cell of cycle page 245 of text
The Cell Cycle - series of events that cells
go through as they grow and divide

The cell cycle is
divided into two
halfs
 Interphase period of the cell
cycle between
cell divisions
 M phase –
period of time
when mitosis
and cell division
occurs
Parts of Interphase

G1 Phase
 Growing

S Phase
 Chromosomes(DNA) are
replicated

G2 Phase
 Organelles and molecules
for cell division are
produced (centrioles)
Chromatin and Chromosomes
Chromatin - A complex of DNA and proteins
in the cell nucleus that condenses to form
chromosomes during cell division.
 Chromosomes – Condensed Chromatin
 They are the same stuff, just in different
forms

Chromatin condenses in chomosomes
before mitosis begins

Chromatin

Chromosomes
Chromosomes

Different organisms have different #’s of
chromosomes
cells – 46
 Fruit Fly cells – 8
 Carrot cells – 18
 King Crab cells - 208
 Humans
Chromosomes Replication



During the cell cycle (before
cell division can take place)
chromosomes are replicated
to form an identical copy of
itself.
Two identical copies of a
chromosome are called
“sister” chromatids – (one of
two identical “sister” parts
of a duplicated
chromosome)
Centromere - area where
the chromatids of a
chromosome are
attached
M Phase, Cell Division and Mitosis
Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
Cytokinesis
-Cytoplasmic
division and
other changes
exclusive of
nuclear
division that
are a part of
mitosis or
meiosis.
In plant cells, a cell plate forms. The cell plate is
synthesized by the fusion of multiple membranebounded vesicles. Their fusion supplies new plasma
membrane for each of the two daughter cells. Synthesis
of a new cell wall between the daughter cells then
occurs at the cell plate.
10-3 cell cycle regulation

Homework 10-3 guided reading workbook
Checkpoint
1. The break down of a cell’s entire life is the
_______ ________.
 2. The phase of the cell cycle when the cell
is growing, replicating DNA and getting ready
for mitosis is _____________.
 3-6. What are the four phases of Mitosis?
 7. The process of a cell actually splitting in
two is called _______________.

Controls on Cell Division
How do cells know when to divide
and when not to?

Internal regulators – are proteins that
respond to events inside the cell.
Some proteins make sure cells do not enter
mitosis until all of the chromosomes have been
replicated.
 What stage of the cell cycle do you think these
proteins work?
 G2 phase


Cyclins – (internal regulator) one of a family
of closely related proteins that regulate the
cell cycle in eukaryotic cells
Cyclins
Protein that periodically
rises and falls in
concentration in step with
the eukaryotic cell cycle.
Cyclins activate crucial
protein kinases (called
cyclin-dependent protein
kinases, or CDK) and
thereby help control the
progression from one stage
of the cell cycle to the next.
Cascade of events!!
Cyclins
External Regulators




External regulators - Proteins that respond to
events outside the cell are called external
regulators.
External regulators direct cells to speed up or slow
down the cell cycle.
Growth factors are among the most important
external regulators, which tell cells to speed up
division. When is this important?
Molecules found on the surfaces of neighboring
cells often have an opposite effect, causing cells to
slow down or stop their cell cycles.
Uncontrolled Cell Growth

Cancer cell

Various forms of cancer have many causes
 Smoking
 Radiation
 Viral
infections
The common thread in all cancers is that
control over the cell cycle has broken down.
 Over 50% of cancer cells have a defect in
the p53 gene.

Quiz on Thursday
HO due wednesday
p53 antioncogene


p53 is a tumor
suppressor gene
found mutated in
about half of
human cancers.
It encodes a gene
regulatory protein
that is activated by
damaged DNA and
is involved in
blocking further
progression of the
cell cycle.
Oncogenes
SRC, proto-oncogene tyrosine-protein kinase