The Cell Growth & Division


2 main reasons cells divide rather than continuing to grow indefinitely:
 When cell increases in size it does not make extra copies of DNA
 If cell grew without limits “information crisis” would occur.

 Food, oxygen, & water have to enter the cell through the cell membrane
 Waste products have to leave
 The rate at which this exchange takes place depends on the surface area of the cell (total area of the cell membrane)


Ratio of Surface Area to Volume
– Volume increases more rapidly than the surface area
– Therefore, ratio of surface area to volume decreases
This decrease causes serious problems for the cell
– If too large becomes to difficult to get enough oxygen and nutrients in and wastes out
This is why cells do not grow much bigger even if the organism of which they are a part of does.
Quick Lab (p. 242) Analyze & conclude 1-2


Define from the chapter:
3.
4.
1.
2.

Cell Division
Mitosis
Chromosome
Chromatid
Draw a picture of chromosome &
Chromatid


Define from the chapter:
5.
Centromere
6.
Cell cycle
7.
Spindle fibers
8.
Centrioles

Draw a picture of Centrioles & Spindle fibers


Cell Growth

Describe:
 G1- period of activity in which cells do most of their growing. Cells increase in size and synthesize new proteins and organelles
 S- Chromosomes are replicated and synthesis of DNA molecules takes place
 G2- Many organelles and molecules required for cell divisions are produced
 M phase- Mitosis
A d d C o l o r !


Draw, label, & describe the phases of:

Interphase

Prophase
A d d C o l o r !


Draw, label, & describe the phases of:

Metaphase

Anaphase
A d d C o l o r !


Draw, label, & describe the phases of:
–Telophase
–Cytokinesisfor both plant & animal
A d d C o l o r !

Regulating the Cell Cycle :
Cell cycle regulators-
– early 1980’s biologists found a protein that increased & decreased the time with the cell cycle
– They called it cyclin because it seemed to regulate the timing of the cell cycle
– Since, they have discovered a whole family of cyclin proteins

Two types of Regulator Proteins
1.
Internal Regulators- proteins that respond to events inside the cell
– Allows cell cycle to proceed only when certain processes have occurred inside the cell
– Ex: doesn’t let the cell enter mitosis until all chromosomes have been replicated
2.
External Regulators- Proteins respond to events outside the cell
– Direct cells to speed up or slow down cell
– Ex: Growth factors- stimulate growth & cycle division of cells. Important in embryonic cells & wound healing

Uncontrolled Cell Growth
Cancer- 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, they divide uncontrollably & form masses of cells called tumors that can damage surrounding tissue.

Two types of tumors:
1.
2.
Benigndoes not spread to surrounding tissue (non cancerous)
MalignantSpreads & destroys healthy tissue (cancerous)
Causes:
1.
2.
3.
Biological Agent- viruses
Chemical Agent- carcinogens- tobacco
Physical Agent- radiation

Treatments:
1.
2.
Surgery
Radiation
3.
Chemotherapy
Write a paragraph of your Opinion on Stem
Cell Research (p. 253)