Chapter 10 Notes
10.1 Cell Growth
The larger a cell becomes the more difficult it is to move enough
nutrients and wastes across the cell membrane.
In addition “DNA overload” could occur. DNA overload
happens when demands on the DNA are too great and it cannot
provide enough information for the growing cell.
Ratio of Surface Area to Volume
As a cell increases in size, its volume increases faster than its
surface area.
Surface Area increases by the square
SA = L x W x 6 (cm2)
Volume increases by the cube
V = L x W x H (cm3)
Figure 10-2
Division of the Cell
Before a cell becomes too large, a growing cell divides forming
two “daughter” cells.
The process by which a cell divides into two new daughter cells
is called cell division.
10-2 Cell Division
Cell cycle is separated into three main parts.
1. Interphase
2. Mitosis (M Phase)
3. Cytokinesis
Interphase –
the period of growth that occurs between cell
division.
Interphase is composed of three parts – G1, S, G2
G1 – Growth phase #1, during this phase cells
increase in size and synthesize new proteins
and organelles.
S - Synthesis,
during
this
phase
the
chromosomes are replicated (DNA is
synthesized).
G2 - Growth phase #2, during this phase cells
continue to replicate organelles and
molecules required for nuclear division are
produced.
Cell division included Mitosis (M phase) and cytokinesis.
Mitosis (M phase) is division of the cell nucleus and is broken
down into 4 main phases and can last from a couple of minutes
to several days.
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Prophase -
(longest phase of mitosis)
Chromosomes condense and become visible
Nuclear membrane breaks down
Nucleolus disappears
Centrioles migrate to opposite poles
Spindle fibers begin to form
Metaphase -
Chromosomes line up across the center of the
cell.
Each chromosome is connected to a spindle fiber
at its centromere.
Anaphase -
Spindle fibers separate sister chromatids and
move them to opposite sides of the cell.
Telophase -
Chromosome begin to unwind.
Two new nuclear membranes begin to form.
Spindle fibers begin to break up.
Cytokinesis
- division of the cytoplasm
Takes place at the same time as telophase
Figure 10-4
Cell Cycle
Chromatids
- one of two identical “sister” parts of a
duplicated chromosome.
Centrioles
- help form spindle fibers during cell division.
Spindle
- made of microtubules and help move and
separate the chromosomes during cell division.
10-3 Regulating the Cell Cycle
Proteins called cyclins regulate the cell cycle.
Internal regulators allow the cell to proceed only when certain
processes have happened inside the cell.
External regulators such as growth factors will cause the cell
cycle to speed up or slow down and responds to external stimuli.
Cancer is a 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 cells.
Tumor = mass of uncontrollably dividing cells.
When a tumor stays in place it is called benign.
When some tumor cells break off and travel to different parts of
the body they are called malignant.