10.1 Cell growth, division, and reproduction
Limits to Cell Size
We learned in Chapter 7, that small cells are more
efficient than large cells.
•The larger a cell becomes,
• the more demands the cell places on its DNA
• the less efficient in moving nutrients and waste materials
across the cell membrane.
An adult produces 25 million new cells per second.
Why do cells divide?
Unicellular organism developing into a multicellular organism
Renewal and Repair of damaged cells
In each situation DNA must be present in each new
When a cell divides the DNA is copied and distributed
so that each cell ends up with an exact copy of the
• Prokaryotic cells reproduce by binary fission
• Produces identical offspring where a parent passes exact copies
of its DNA to its offspring.
Eukaryotic organisms can also reproduce asexually.
• Budding forms a new organism from a small projection
growing on the surface of the parent.
• Fragmentation is the splitting of the parent into
pieces that each grow into a new organism.
• Involves the fusion of two parent cells
• Offspring inherit some information from each parent
10.2 THE PROCESS OF CELL DIVISION
CHROMOSOMES – condensed chromatin
•A single molecule of DNA has thousands of genes
•DNA is arranged into chromosomes
• Prokaryotes – single circular chromosome in cytoplasm
• Eukaryotes – multiple chromosomes are located in the nucleus
• Each chromosome is made up of 2 sister chromatids
• The sister chromatids are attached at a centromere
Condensed, duplicated chromosome
Chromosomes in Sexual Reproduction
• Somatic Cell – normal body cell, not a sperm or egg cell.
• In a normal human contains 46 chromosomes
• Gamete – sex cell, sperm or egg
• In a normal human contains 23 chromosomes
• When two haploid gametes fuse in fertilization, the
result is a diploid zygote (the first cell of a new
The Cell Cycle
The cell cycle is a regular pattern of growth, DNA
replication, and cell division.
Stages of the Cell Cycle
• G1: cell growth and normal
• S (synthesis): copies DNA
• G2: additional growth and
preparation for division
• Cell Division (M phase)
• division of the cell nucleus
• division of the cell cytoplasm
Before cell division can begin the cell will go
Parent cell in Interphase
Steps of Mitosis
• Step I: Prophase
• chromosomes condense
• Spindle fibers form from centrioles.
• Nucleolus disappears and the nuclear envelope breaks down
• Step 2: Metaphase
• Centromeres of chromosomes line up in the middle of the cell
• Spindles attach to centromeres
• Step 3: Anaphase
• sister chromatids separate and move along the spindle fibers to
opposite sides of the cell
• Step 4: Telophase
the new nuclear envelopes form and chromosomes begin
to uncoil into chromatin
Mitosis is complete! (cell division still has one more step)
• In animal cells, the membrane pinches closed.
• In plant cells, a cell plate forms.
• After cytokinesis in all cells, each new cell begins
• Cells Alive Animation
Compare asexual and sexual reproduction.
How does cytokinesis compare in plant and animal
Describe the relationship between the following
terms: chromatin, chromosomes, chromatid, and
10.3 regulating the Cell Cycle
• One of the most important internal factors that
regulate the cell cycle are:
• Cyclins (regulatory proteins)
• Normal cells stop
dividing when they
touch each other.
• If one of these factors is mutated regulation of
growth and division can be disrupted.
• Cancer cells do not respond normally to the
bodys control mechanisms.
• As a result they divide uncontrollably and form a mass
of cells called a tumor.
10.4 Cell Differentiation
• As a zygote grows into stem
cells, and then an embryo, the
cells become specialized
through the process of
• Differentiated cells are specialized
to perform certain jobs.
• Example: nerve cells, muscle cell,
blood cell, skin cell