Cell Growth and

Division

Chapter 10

Why Cell’s Divide . . .

As volume increases:

•More demand placed on cell’s DNA (DNA Overload)

•More difficult to bring in enough nutrients and get rid of waste (material exchange)

Surface area increases at a slower rate

Limits on Cell Growth

Volume

•V=4/3 Pi r3

Surface area

•SA=4 Pi r2

Cells divide rather than

grow indefinitely

Before a cell gets too

large it undergoes . . .

Cell Division – a cell divides into two new daughter cells

Cell Cycle and

Division

Section 10 -2

Cell Cycle

Describes the events a cell undergoes as it grows and divides.

Cell Cycle (phases)

G1 (primary growth phase) –cell gets bigger

S (synthesis)- DNA is replicated

Cell Cycle (phases)

G2 (gap 2) –cell prepares to divide, organ-elles replicate

M (mitosis)- cell nucleus divides into two (PMAT)

Cell Cycle (phases)

C (Cytokinesis)- cell cytoplasm divides resulting in two daughter cells

Cell Cycle (phases)

Interphase- cell resting (G1, S, G2)

M Phase- Cell actively dividing (M, C)

Cell Division (2stages)

Mitosis – nucleus splits (2 nuclei)

Cytokinesis-cytoplasm divides (2 daughter cells)

Mitosis

The division of the cell’s nucleus.

4 Stages (PMAT)

Prophase

Chromosomes condense

Centrioles move to opposite poles

Nuclear envelope breaks down

Metaphase

Chromosomes line up in the middle of cell

Chromosomes connect to spindle fibers

Anaphase

Sister chromatids separate at centromere

Sister chromatids move to opposite poles

Telophase Chromosomes gather at opposite ends (start to unwind)

Spindles break down

Nuclear envelope re-forms

Cytokinesis

Cytoplasm pinches in half

Result: Two identical daughter cells

Regulating the Cell

Cycle

Cyclins

A family of Proteins

Regulate the timing of the cell cycle

2 types: •Internal regulators

•External regulators

Cyclins

Internal – conditions inside the cell must be met (ex DNA Replication completed)

External- inhibitors on the surface of neighboring cell prevent cell division

Cancer

Don’t respond to signals regulating growth

Cells divide uncontrllably

•Tumors – mass of cancer cells