Chapter 10 Cell Growth and Division

Chapter 10 Cell Growth

and Division

Limits to Cell Growth• The larger a cell becomes,

the more demands the cell places on its DNA and more trouble the cell has moving enough nutrients and wastes across the cell membrane

Growing Cells 1µ 2µ

3µ

4µ 6

5µ 6µ

How are surface area and volume affected by growth

Size / µm

1 2 3 4 5 6

Surface area / µm2

6 24 54 96 150 216

Volume / µm3

1 8 27 61 125 216

SA/V 6 3 2 1.5 1.2 1

DNA “Overload”• In Eukaryotic Cells, DNA is found in the

nucleus • As a cell increases in size, it does not

make extra copies of DNA• “Information Crisis” would occur if a

cell was to grow without limit• In time, the cell’s DNA would no longer

be able to serve the increasing needs of the growing cells

DNA “Overload”• There is another reason why the size of

cells are limited. • The rate of exchange depends on the

surface area of the cell. • The total area of its Cells Membrane• Rate at which food and oxygen are used

and waste products are produced depends on a cell’s volume

DNA “Overload”• Volume increases much more rapidly

then the surface area• It would be more difficult for a

larger cell to get oxygen and nutrients in and waste products out.

Cell Division Process by which a cell divides into two

daughter cells • Before it becomes too large, a growing

cell divides forming two “ Daughter” cells

• The cell replicates, or copies its DNA • Each daughter cell receives its own

genetic “library”

Chromosomes• Genetic information is passed on by

chromosomes• Chromosomes are made up of DNA and

Proteins• Cells of every organism have a specific

number of chromosomes• Chromosomes are not visible except

during cells division• Chromosomes condense at the

beginning of cell division

Chromosomes• Each chromosome s is replicated before

cell division because of this, each chromosome consists of two identical “Sister” chromatids

Chromatids• Attach at the centromere located

near the middle of the chromatids

Cell Cycle• A series of events that cells go

through as they grow and divide• During the cell cycle, a cell grows,

prepares for division, and divides to form tow daughter cells, each of which then begins the cycle again

Mitosis

I Prefer Mangos And Tangerines• Biologists divide the events of

mitosis into phases:• Interphase• Prophase• Metaphase• Anaphase• Telophase

Mitosis in ActionBlue shows DNA, Green shows

spindle fibers

Interphase• Has three phases: G1, S, & G2• G1 – Cells do most of their growing• S- Chromosomes are replicated and

the synthesis of DNA molecules take place

• G2 – shortest phase organelles and molecules required for cell divisions are produced

Prophase• The longest and first phase• Chromosomes becomes visible• Centrioles separated and take up

positions on opposite sides of the nucleus

• Centrioles help organize the spindle:– Fan like microtubule structure that

helps separate the chromosomes

Metaphase • The second phase• Chromosomes line up across the

center of the cell

Anaphase• The third phase• He centromeres separate allowing

the sister chromaids to separate

Telophase• The final phase• The chromosomes begin t disperse

into a tangle of dense material• A nuclear envelope reforms• Spindle begins to break apart• Nucleolus becomes visible • Mitosis is complete

Cytokinesis• Division of the cytoplasm itself• Occurs at the same time as

telophase

Cell Cycle Regulators • Cyclin

– Protein that regulates the cell cycle– Regulate the timing of the cell cycle in

Eukaryotic cells

Internal Regulators• Protein that respond to events inside

the cell are called Internal Regulators

External regulators• Proteins that respond to events

outside the cell are called external regulators

• Direct cells to speed up or slow down the cell cycle

Uncontrolled Cell Growth• Cancer

– A disorder in which some the body’s own cells lose the ability to control growth

– Cancers cells do not respond to the signals that regulate the growth of most cells

– As a result, they form masses of cells called Tumors that can damage for surrounding tissues.

Cancerous Tumor