Transcript Cell Growth and Division

Cell Growth and Division
Chapter 10
Cell Growth
Does an adult have bigger
cells than a child?
Limits to Cell Growth
• Why do cells divide instead of continuing
to grow?
1. DNA overload – too much strain on
DNA info to run cell.
2. Cell volume increases too rapidly for
surface area (cell membrane). Inefficient
material exchange. Too much stuff!
• Solution: Divide or Die!
Ratio of Surface Area to
Volume in Cells
Section 10-1
Cell Size
Surface Area
(length x width x 6)
Volume
(length x width x height)
What is another reason, other than cell growth, that would cause
cell division to occur? (Hint: when do we need to get new cells?)
Some cells can readily divide, but some may rarely or never divide.
Cell Division
What is the necessary
material for a new cell to
have in order to function?
What Are Chromosomes?
• Strands of DNA
• Every organism has a specific number of
chromosomes. How many do humans cells have?
• Before cell division occurs, DNA must be copied
so each new cell will have DNA instructions.
• Once copied, the two identical strands (or
CHROMATIDS) are held together by a
CENTROMERE.
centromere
Draw this in your NB!
Chromosome
(uncopied)
Chromosome
(copied)
chromatid
Cell Cycle – “Life of a Cell”
• Interphase – growth period of cell, longest stage
of cell life.
1. G1 phase – growth, more organelles
2. S phase – DNA duplication
3. G2 phase – preparation for mitosis, last
check
• Cell Division – division of the cell into 2
1. Mitosis – division of the nucleus
2. Cytokinesis – division of the cytoplasm
Study this diagram!
Pg. 245 in book
Section 10-2
G1 phase
M phase
S phase
G2 phase
Mitosis
• Prophase - Chromosomes become visible,
centrioles move to opposite sides of cell (animal
cells only), spindle forms, nuclear membrane
breaks down
• Metaphase - Chromosomes line up in middle,
spindle fibers attach to centromeres
• Anaphase - Sister chromatids are separated
into individual chromosomes
• Telophase - chromosomes gather at opposite
sides of cell, new nuclear membranes form
Mitosis Animation
Interphase
Prophase
Metaphase
Anaphase
Telophase
Animal Cell
Onion root tip –
active growing
region…this
means lots of
mitotic cells!
Hint:
If you see a NUCLEOLUS, it is in interphase.
If you can see snake/fingerlike chromosomes, it is in a stage of
mitosis.
Prophase? Metaphase? Anaphase? Telophase?
1
3
2
4
5
6
Prophase? Metaphase? Anaphase? Telophase?
1
2
5
3
6
4
7
Cytokinesis
• Division of the cytoplasm
• This process starts during telophase
• In animal cells: cleavage of cell
membrane.
• In plant cells: a cell plate forms
midway between the divided nuclei.
Cell Plate Forming
Cleavage or Pinching in
Cell Cycle and Cell Division Animation
Animation #2
Question: Will the new cells
have the same, more or less
chromosomes than the mother
cell?
What happens if something goes
wrong with the cell cycle?
Cancer
• Uncontrolled cell division
• DNA is damaged by carcinogens or
genetically inherited.
• Cell will not respond to cell cycle
regulators.
• Carcinogens can be radiation,
chemicals or viral
Stem Cells
• Cell that have not become
specialized.
• Stem cells can become
any type of human cell.
Abundant in embryos.
• Possible uses in science:
treating nerve damage,
growing organs, treating
diseases.