1. Ch 10- Cell Growth What problems does growth cause for the cell?
Larger a cell becomes, the more demands that cell places on its DNA
The cell has more trouble moving enough nutrients and wasted across the cell membrane
Where is the information that tells cells what to do stored at?
DNA
Understanding the relationship between a cell’s volume and surface are is key to understanding why cells must divide as they grow

2. Division of the Cell
If cell got to large, it would be more difficult to get sufficient amounts of oxygen and nutrients in and waste products out
Cell division- process by which a cell divides into two new daughter cells
Copies DNA, each daughter cell gets one complete set of genetic information- solves the problem of information storage
Solves the problem of increasing size by reducing cell volume- each daughter cell has an increased ratio of surface area to volume

3. Sec 2- Cell Division
Prokaryotes- process of cell division is simply separating the contents of the cell into two parts
Eukaryotes- process is more complex and occurs in 2 stages
Mitosis- division of cell nucleus
Asexual, cells produced are identical to parent cell
Source of new cells as multicellular organism grows and develops
Begins shortly after egg is fertilized
Cytokinesis- division of cytoplasm

4. Chromosomes What are they? How many chromosomes do human cells have?
Carries the genetic information passed from one generation to the next, made of DNA and proteins
How many chromosomes do human cells have? 46
Fruit flies have 8 chromosomes
Not visible except during cell division
Before cell division, chromosomes are replicated
Each chromosomes consist of 2 identical “sister” chromatids- when cell divides one chromatid goes to each of two new cells
Centromeres- area where chromatids are attached, usually located near middle

5. Cell Cycle
During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cycle again
Interphase- the in between time between cell division
Cell cycle- series of events that cells go through as they grow and divide
Cell cycle consists of 4 phases
Mitosis and cytokinesis take place during M phase
Chromosome replication takes place during S phase
G phases are periods of intense growth and activity

7. Events of the Cell Cycle
Interphase- phase is quite long, made up of G₁, S, and G₂ phases
G₁ phase- where cells do most of their growing
Cells increase in size and synthesize new proteins and organelles
S phase- chromosomes are replicated and synthesis of DNA molecules takes place
G₂ phase- many of organelles and molecules required for cell division are produced
Cell is ready for the M phase and begin process of cell division

8. Mitosis
Divided into 4 phases- prophase, metaphase, anaphase, and telophase
May last anywhere from few minutes to several days- depends on type of cell
Prophase- chromatin condenses into chromosomes, centrioles separate and a spindle begins to form, nuclear envelope breaks down
Centrioles- two tiny structures located in cytoplasm near nuclear envelope, separate and take position on opposite sides of nucleus
Spindle- fan-like microtubule structure that helps separate the chromosomes

9. Metaphase- chromosomes line up across the center of cell, each chromosome is connected to a spindle fiber at its centromere
Anaphase- sister chromatids separate into individual chromosomes and are moved apart
Telophase- chromosomes gather at opposite ends of cell and lose their distinct shapes, two new nuclear envelopes will form
Mitosis is complete

10. Cytokinesis
Result of mitosis= two nuclei each with duplicate set of chromosomes formed within cytoplasm of a single cell
Cytokinesis- division of cytoplasm, usually occurs at same time of telophase
Cytoplasm pinches in half, each daughter cell has an identical set of duplicate chromosomes
Mitosis and Cytokinesis

11. Sec 3- Regulating the Cell Cycle
Cyclin- proteins that regulate the timing of the cell cycle in eukaryotic cells
Discovered by Tim Hunt and Mark Kirschner
Many more proteins have been discovered since- 2 types of proteins- regulatory proteins in and outside of cell
Internal Regulators- allow cell cycle to proceed only when certain processes have happened inside cell
Make sure cell does not enter mitosis until all chromosomes have been replicated
External Regulators- direct cells to speed up or slow down cell cycle
Growth factors among most important external regulators

12. Uncontrolled Cell Growth
Why is cell growth regulated so carefully?
Cancer- disorder in which some of body’s own cells lose the ability to control growth
Do not respond to the signals that regulate the growth of most cells
Divide uncontrollably and form masses of cells called tumors
May break free from tumor and spread to rest of body
What causes the loss of growth control that characterize cancer?
Smoking tobacco, radiation exposure, viral infection