The Cell Cycle

Why do cells divide?

- Smaller cells are more efficient at:

- Obtaining:O2

H2ONutrients (glucoseamino acids, etc.)

- Ridding themselves of

CO2

wastes

ReproductionReplace damaged cells/RepairAllows organism to grow

Density Dependent Inhibition - Space fills, division stops

- Meeting the demands on their DNA

Which of the following “cells” functions more efficiently?

1. The larger one

2. The smaller one

Mathematical Proof:

Surface Area Volume

cm2

cm3

Compare:

1cm 3cm

Surface Area = 1x6 = 6 Volume 1x1x1 1

Surface Area = 1x6(9) = 54 = 2 Volume 3x3x3 27 1

More surface area per unit of volume

Less surface area per unit of volume

Cell CycleSo cells divide to stay small and efficient.

Let’s look at their life cycle:G Phases = intense growth intense activity

S Phases = DNA synthesis

How long does this all take? Depends on the type of cell!

Skin cells – 2 or less hrsDigestive – 6 hrsNerves – don’t

Chromosome division and separation

Interphase: G1, S, G2Mitosis: Cell division

Chromosome Changes During Cell Cycle

Chromosome

Sister Chromatids joined by a Centromere

Chromosomes headed for 2 separate daughter cells

Chromatin

Cell Division

Cell Division occurs in two ways: to produce two different kinds of cells for two different functions

Mitosis produces genetically identical daughter cells that will take over the job of the parent cellMeiosisproduces genetically different cells that will be used in sexual reproduction,,,egg + sperm

Mitosis

Occurs in 4 (5) stages:

ProphaseMetaphaseAnaphaseTelophase

(Cytokinesis)

Describe changes involving DNA

Describes changes involving cytoplasm and the rest of the cell

Interphase

Centrioles

Cell is full sizedNucleus is intactDNA has already been replicatedCentrioles (animal cells only) are prepared to assist in division

Animal CellPlant Cell

Quick Quiz!! What kind of cell is this most likely to be?

0%0%

A. AnimalB. Plant

Response Grid

Prophase

Plant Cell

Early Late

Animal Cell

Chromosomes formNuclear envelope breaks upNucleolus breaks upSpindle apparatus formsCentrioles (animal cells only) move

to opposite ends of the cell

Metaphase

Animal Cell

Plant Cell

Chromosomes line up in the middle of the cellCentrioles (animal cells only) are as far apart as possibleSpindle attaches to centromeres

Anaphase

Animal Cell

Plant Cell

Sister chromatids separateSpindle shortensCytokinesis begins

Animal Cells = “pinching”Plant Cells = cell plate forms

Telophase

Animal Cell

Plant Cell

Chromosomes have moved to opposite ends of the cellChromosomes begin to unwind into chromatinNuclear envelope begins to reformSpindle apparatus dissociatesCytokinesis continues

Animal Cells = pinching morePlant Cells = cell plate grows until wall is complete

Early Late

CytokinesisCell will separate throughout anaphase and telophaseDaughter cells result; half the size as parent cell at the end of G2

Animal CellPlant Cell

Quick Quiz!! What phase is this?

Pro

phase

Met

apha

se

Anap

hase

Tel

ophas

e

5%0%

10%

86%A. Prophase

B. Metaphase

C. Anaphase

D. Telophase

Quick Quiz!! What phase is this?

Pro

phase

Met

apha

se

Anap

hase

Tel

ophas

e

85%

5%5%5%

A. Prophase

B. Metaphase

C. Anaphase

D. Telophase

Quick Quiz!! What phase is this?

Pro

phase

Met

apha

se

Anap

hase

Tel

ophas

e

5%

29%

62%

5%

A. Prophase

B. Metaphase

C. Anaphase

D. Telophase

Quick Quiz!! What phase is this?

Pro

phase

Met

apha

se

Anap

hase

Tel

ophas

e

0% 0%

95%

5%

A. Prophase

B. Metaphase

C. Anaphase

D. Telophase