CHAPTER 10 GROWTH AND DIVISION

Cell reproduction is different in prokaryotes than in eukaryotes.

Prokaryotes Lack a nucleus Have a single chromosome Reproduce by binary fission

E. Coli Reproducing by binary fission

Eukaryotes Have a nucleus and membrane bound organelles Reproduce by mitosis (asexual) Daughter cells Parent Cell

In most cases, living things grow by producing more cells.

2 main reasons why cells divide are: 1) too large a demand on DNA 2) difficulty moving enough materials across the cell membrane

If a cell continued to grow larger without dividing, its DNA would no longer be able to meet the cell’s needs

The rate of exchange of materials across the membrane depends on the surface area of the cell; while the rate at which food and oxygen are used up and wastes are produced depends on the cell’s volume.

As a cell increases in size, the volume increases much more quickly than the surface area. this causes problems in moving sufficient materials across the membrane.

Cell division solves the problem of moving enough materials by increasing the surface area of the cell and solves the problem of insufficient DNA by replicating the chromosomes (making a copy of the DNA).

Before it becomes too large, a growing cell divides forming two “daughter” cells in the process called cell division.

CELL CYCLE

Phases of the Cell Cycle G1 phase S (synthesis) phase G2 phase M phase (mitosis) G1, S, and G2 are collectively called Interphase.

Interphase

G1 Phase First growth stage Cell increases in size Synthesize new proteins and organelles

S phase DNA molecules are synthesized Chromosomes duplicated

G2 phase Time between DNA synthesis & mitosis Cell continues growing Needed proteins and organelles produced

M Phase Cell growth & protein production stop Cell’s energy used to make 2 daughter cells Called mitosis or karyokinesis (nuclear division) Only occurs in eukaryotes

Mitosis is M phase or Divided into 4 sub phases: Prophase Metaphase Anaphase Telophase

Cells Undergoing Mitosis

Prophase Longest phase Chromosomes become visible Centrioles move to poles of cell Nuclear membrane breaks down Nucleolus disappears Chromosomes attach to spindle at centromere

Nucleus & Nucleolus have disintegrated Cytoplasm Nucleolus Nuclear Membrane Chromosomes Chromosomes Nucleus & Nucleolus have disintegrated

Human Chromosomes

Metaphase Chromosomes line up along equator of cell Microtubules connect centromeres to pole of spindle

Metaphase

Steps in Anaphase Chromosomes are separated Spindle fibers shorten so are pulled to poles of cell

Mitotic Spindle

Anaphase

Steps in Telophase Separation of chromosomes completed Cell plate forms (plants) Cleavage furrow forms(animals) Nucleus & nucleolus reform Chromosomes uncoil

Telophase        Plant             Animal

Cytokinesis Occurs after chromosomes separate Forms two, identical daughter cells

Cytokinesis Cleavage furrow in animal cell Cell plate in plant cell

No. All cells do not move through the cell cycle at the same rate No. All cells do not move through the cell cycle at the same rate. Muscle cells and nerve cells do not divide once they have developed. 51. Skin, digestive tract, and bone marrow cells divide rapidly throughout life.

Yes. The controls on cell growth and cell division can be turned on and off. The process of cell division is turned on when an injury occurs. The cells at the edge of the injury are stimulated to divide rapidly.

Cancer is a disorder in which some of the body’s own cells lose the ability to control growth.

Cancer cells do not respond to the signals that regulate the growth of most cells. Cancer cells divide uncontrollably and form masses of cells called tumors. Tumors are harmful because they damage surrounding tissues.

Cancer may be caused by tobacco, radiation, or viral infection Cancer may be caused by tobacco, radiation, or viral infection. All cancers have one thing in common: The control over the cell cycle has broken down.

A large number of cancer cells have a defect in the p53 gene A large number of cancer cells have a defect in the p53 gene. The p53 gene normally halts the cell cycle until all chromosomes have been replicated.

Mitosis Animation Name each stage as you see it occur?

Test Yourself over Mitosis

Mitosis Quiz

Name the Stages of Mitosis: Early prophase Early Anaphase Metaphase Interphase Early Telophase, Begin cytokinesis Late Prophase Late telophase, Advanced cytokinesis Mid-Prophase Late Anaphase

Identify the Stages ? ? ? ? ? ? ? Early, Middle, & Late Prophase Metaphase Anaphase Late Prophase ? ? ? Telophase & Cytokinesis Late Anaphase Telophase

Locate the Four Mitotic Stages in Plants Anaphase Telophase Metaphase Prophase