CELLULAR GROWTH
Ch 9.1
Surface Area To volume Ratio
• Surface Area to volume ratio limits size
• As surface Area Doubles the Volume
increases by 4 times!
• Makes large
Cells less
efficient
Why do cells need to be efficient?
• Transportation:
• Diffusion over large distances is
inefficient and slow
• Small size helps maintain
transportation of substances
Why do cells need to be efficient
• Communication:
• Small cells are able to communicate
cellular instructions better than large
cells.
• Signal molecules move throughout the
cell
The Cell cycle
• A cycle of Cells growing and then
dividing
• When a cell grows too large it divides
into two cells.
• Division is how cells reproduce
Steps of Cell cycle
• Interphase – Cell Grows, carries out
cellular functions and replicates DNA.
Longest Step of cell cycle
• Mitosis – Nucleus and DNA is divided
• Cytokinesis – Cytoplasm is divided
creating 2 daughter cells
Interphase
• The first stage of interphase is G 1
• The Cell grows and functions normally.
Interphase
• The second stage is S
• The Cell copies it’s DNA.
Interphase
• The last stage of interphase is G 2
• The Cell prepares for division
Copy the questions to your notes!
1. What limits Cell size?
Surface area to volume ratio
2. What are the three steps of the cell
cycle Interphase, Mitosis, Cytokinesis
3. Which step is the longest? Interphase
4. What are the three phases of
Interphase?
G1, S, G2
MITOSIS AND
CYTOKINESIS
Chapter 9.2
Mitosis
• Division of the nucleus resulting in 2
identical daughter cells.
• Usually followed by cytokinesis the
division of the cytoplasm.
Genetic Material
• Chromatin – The DNA in the nucleus
(looks stringy)
• Chromosome – A single DNA molecule,
visible as a bar-like structure during cell
division. (human = 46 chromosomes)
Four stages of Mitosis (PMAT)
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
• Chromatin condenses to chromosomes
• Nuclear Membrane and nucleolus
disappear
• Centrioles migrate to poles
• Spindles form
Metaphase
• Spindles attach to chromosomes
• Chromosomes line up along the
middle of the cell
Anaphase
• Sister chromatids separate
• Chromosomes move toward the poles
Telophase
• Chromosomes arrive at poles
• New nuclear membrane begins to form
• Spindles disassemble
Cytokinesis
• Animals – microfilaments wrap around
cytoplasm and pinch it to separate.
• Plant – a new structure called a cell
plate forms to divide the two cells.
Copy the question to your notes!
1. How many chromosomes do humans
have?
46
2. Before Chromosomes condense during
mitosis they are stringy and called
Chromatin
_______________.
3. What are the four stages of mitosis?
Prophase, Metaphase,anaphase,Telophase
4. What happens after mitosis is finished?
cytokinesis
Normal Cell cycle
• The cycle has built in checkpoints that
monitor the cycle and can stop it if
something goes wrong.
Abnormal Cell cycle: Cancer
• Cancer is uncontrolled cell growth and
division
• Cancer cells can crowd out normal
cells and kill an organism.
• Cancer cells do not
grow like they should.
Causes of Cancer
• Genetics
• Changes during cell cycle regulation are
due to DNA mutation
• Inherited genes
• Genes getting old
• Environmental effects
• Carcinogens cause cancer
• Examples: Tobacco, Ultraviolet radiation
Apoptosis
• Apoptosis is programmed cell death
• Cells shrink and shrivel in a controlled
way.
Stem cells
• Unspecialized cells that can develop
into specialized cells under the right
conditions.
Copy the questions to your notes!
1. What is built in to monitor the cell
cycle? Check points
2. Uncontrolled cell growth is called
Cancer
____________.
3. Programmed cell death is called
Apoptosis
____________.
4. These cell are unspecialized and can
turn into specialized cells in the right
environment. Stem cells