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Chapter 5
Lecture Notes
5-1
Cell Growth & the cell cycle
As a cell double in diameter it’s surface area increases
by four while it’s internal volume increases by eight.
Cell Size
Volume (LxWxH)
Surface Area (# of surfaces xLxH)
Surface Area/Volume Ratio
1cm lcm x lcm x lcm = lcm3 6 x lcm x lcm = 6cm2
2cm 2cm x 2cm x 2cm = 8cm3 6 x 2cm x 2 cm = 24cm2
6cm2/lcm3 =6/cm
24cm2/8cm3 = 3/cm
Cell Cycle
 In most cases > a cell will increase in size > then
divides into two cells.
 This process is a regular series of events called the
cell cycle.
 The cell cycle is the period of time from the
beginning of one cell division to the beginning of the
next.
Cell Cycle
 Consist of 4 phases:
 G1 Most of the cells growth and activity
 S Chromosome replication takes place
 G2 Final preparations for cell division
 M Cell Divison takes place (Mitosis)
 Cell Division is the process in which the cell divides into two
independent cells called daughter cells.
 Daughter cells are the end result of cell division.
 Cancer  Uncontrolled cell growth
Cell Cycle
Graphics drawn by Jacob Rondinella
5-2
Cell Division
- In prokaryotic (lacks nucleus) the cell divides by
simple division. (Binary Fission)
-In Eukaryotic cells, division is more complex
Interphase
 Makes up the G, S, + G2 phases of the cell cycle.
 Occurs between cell division.
 Chromosomes are not visible.
 1. Chromosomes unfold
Mitosis (cell division)
 Prophase
 MetaPhase
 Anaphase
 Telophase
Prophase
1. Longest phase
2. Chromosomes appear
3. Each chromosome consists of two identical strands
called sister chromatins that are attached at an area
called the centromere.
4. Centrioles separate and more to opposite sides of
the nucleus.
Metaphase
1. Shortest phase
2. Chromosomes line up in the center of the cell.
Anaphase
1. Sister chromatids split at the centromere an move
towards opposite ends of the cell.
2. Anaphase stops when the chromosomes stop
moving.
3. Cytokinesis begins.
Telophase
1. Chromosomes start to spread out.
2. Nuclear membranes form around each cluster.
3. Cytokinesis is still happening.
Cytokinesis
1. Division of the cytoplasm.
2. Helps to form two new daughter cells.
46 Chromosomes in a normal cell
Sperm & egg- 23 chromosomes each
Chromatin  DNA + Histones
Chromosomes  When the chromatin coils tightly
Chromatids  When the chromosomes replicate
5-3
Cell Specialization
That specific cells are suited to carry out specific
function
Macrophages  Cell that provides protection.
Travel through the bloodstream.
Fight bacteria + germs.
Neurons  Message carrying cell found in the nervous system.
Long and then cells.
They carry electrical impulses.
Levels of Organization
Tissue – group of cells that perform similar function.
Organs – group of tissues
Organ System – group of organs that perform function
5-4 Controlling Cell Cycle
Cyclins regulate / Control the Cell Cycle
P188 #1-12