Download Chapter 10-1:

G1
phase
Chapter 10-1: Cell Growth
When an organism grows, the number of cells increase but the size of each cell remains small.
Limits to Cell Growth
1.
DNA “overload”: The larger a cell becomes, the more demands the cell places on its DNA.
a. DNA stores the information that controls how a cell functions
M phase
b. When a cell is small, DNA can meet the cells needs
c. When a cell is large, it still has only one copy of DNA so it is more difficult for the cell to perform its function
2.
Exchanging materials: In addition, large cells have more trouble moving substances across the cell membrane.
a. If a cell is too large, it is difficult to get enough oxygen and nutrients in and waste products out
G2
b. This is why cells do NOT grow much larger even if the organism does grow large
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Division of the Cell
1. Before a cell gets too large, it will divide to form two “daughter” cells
2. Before a cell divides, it makes a copy of its DNA for each daughter cell
Chapter 10-2: Cell Division
1.
Cell division in eukaryotes is more complex than in prokaryotes.
2.
There are two stages of eukaryotic cell division
a. Mitosis: Division of the cell nucleus
b. Cytokinesis: Division of the cell cytoplasm
3.
Unicellular organisms reproduce asexually by mitosis
a. The daughter cells are identical to the parents cells
4.
Mitosis is how a multicellular organism grows and develops
Chromosomes
1. Chromosomes are made of condensed chromatin.
2. Chromatin consists of DNA and the proteins it is wrapped around.
3. The cells of every organism have a specific number of chromosomes (humans have 46 chromosomes).
4. Chromosomes are only visible during cell division, when they are condensed. The rest of the time the chromatin is spread throughout the nucleus.
5. Before cell division, each chromosome is replicated (meaning copied).
a. When a chromosome is replicated, it consists of two identical “sister” chromatids.
b. When a cell divides the chromatids separate, and one goes to each of the two new cells.
c. Sister chromatids are attached to each other at the spot called the centromere.
The Cell Cycle: When a cell is not dividing, it is said to be in interphase. The series of events that a cell goes through as it grows and divides is called the cell cycle.
Events of the cell cycle Interphase, when the cell is not dividing, has three phases: G1, S, and G2.
1.
G1 phase: period of activity in which cells do most of their growing.
a. Cells increase in size
b. Cells synthesize (make) new proteins and organelles
2.
S phase: DNA (chromosomes) is replicated
3.
G2: organelles and molecules requires for cell division are produced
M phase is the phase of cell division. This includes:
1.
Mitosis, the division of the cell nucleus, which is made up of four segments including prophase, metaphase, anaphase, and telophase.
2.
Cytokinesis, or the division of cytoplasm.
S
phase
Mitosis: There are four phases in mitosis:
1.
Prophase
a. Longest phase in mitosis (take 50-60% of total time mitosis requires)
b. Chromosomes become visible because they are condensed
c. Centrioles become visible on opposite sides of the nucleus
i. The centrioles help organize the spindle, a structure made of microtubules that helps separate the chromosomes
ii. Plant cells to not have centrioles but do have mitotic spindles
d. Nucleolus disappears
e. Nuclear envelope breaks down
2.
Metaphase:
a. Chromosomes line up in the center of the cell
b. Microtubules connect to the centromeres
3.
Anaphase
a. Centomeres split and the sister chromatids separate becoming individual chromosomes
b. Chromosomes move and separate into two groups near the spindle
c. Anaphase ends when the chromosomes stop moving
4.
Telophase
a. Chromsomes change form being condensed to dispersed
b. A nuclear envelope forms around each cluster of chromosomes
c. Spindle breaks apart
d. Nucleolus is visible in each daughter nucleus
Cytokinesis: Mitosis occurs within the cytoplasm of one cell. Cell division is complete when the
cytoplasm divides. In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two equal parts. Each part has a nucleus and cytoplasmic organelles.
In plants, a structure called the cell plate forms between the two daughter nuclei. The cell plate develops into a cell membrane and cell wall.
Asexual Reproduction is one cell reproducing by itself. There are 2 types:
1. Binary fission: organism replicates its DNA and divides in half, producing two identical daughter cells example: bacteria
2. Budding: asexual process by which yeasts increase in number
Chapter 10-3: Regulating the Cell Cycle
Different cell types divide at different rates. Muscle cells and nerve cells do not divide once they have developed. Skin cells and cells in the bone marrow that make blood cells
divide rapidly.
Controls on cell division: Cell growth and cell division can be turned on and off.
1.
When you are injured your cells divide rapidly to repair the injury. When the injury has healed, the cells stop dividing.
Uncontrolled cell growth: When cells in your body cannot control cell growth and division, cancer may form.
1.
Cancer cells cannot respond to the signals that regulate the division of cells.
2.
When cancer cells have been dividing uncontrollably, tumors form.
3.
Tumors can damage surrounding tissue.
4.
Cells from tumors can break free and travel to other parts of the body, forming new tumors.
There are several reasons that cells may lose the ability to control growth. Some examples are: smoking, radiation exposure, viral infection
Scientists who study cancer are researching how cells divide.