Cell life cycle (including Mitosis)

Cell life cycle (including Mitosis)

Pg. 151-159Pg. 151-159

All cells pass through a series of events called the cell cycle.

Some cells cycle continually (skin, root tips), other cell types only a limited number of times before they stop multiplying (brain, nervous, etc.) and eventually die.

The cell cycle is divided into several stages.

All cells pass through a series of events called the cell cycle.

Some cells cycle continually (skin, root tips), other cell types only a limited number of times before they stop multiplying (brain, nervous, etc.) and eventually die.

The cell cycle is divided into several stages.

Interphase Interphase Most of cell cycle (95%) = normal cell

functioning Cell increases in size Organelles replicate. DNA replicates. Readies for mitosis DNA condenses Three parts:

G1 = Cell growth; Normal cell functions

S = DNA replicatedG2 = DNA condenses into chromosomes

Strands = sister chromatids2 Chromatids connected by centromere

Most of cell cycle (95%) = normal cell functioning

Cell increases in size Organelles replicate. DNA replicates. Readies for mitosis DNA condenses Three parts:

G1 = Cell growth; Normal cell functions

S = DNA replicatedG2 = DNA condenses into chromosomes

Strands = sister chromatids2 Chromatids connected by centromere

ChromosomesChromosomes The organelle into

which DNA is packaged

Contains proteins called histones – which give DNA support

Chromatin is what DNA is called when it is not tightly coiled during cell division

Chromosomes only “appear when a cell is dividing”

The organelle into which DNA is packaged

Contains proteins called histones – which give DNA support

Chromatin is what DNA is called when it is not tightly coiled during cell division

Chromosomes only “appear when a cell is dividing”

Why divide? Why not increase in size?Why divide? Why not increase in size?

As organisms grow, the size of their cells do not increase they simply divide into more cells!

Cells need a high surface area to volume ratioREMEMBER: Cell membrane lets things in (like

glucose) and removes others (carbon dioxide) Very large cells cannot let things in and out fast

enough to maintain the needs of the larger cell

ANSWER: Cells divide after growth or die because eventually they cannot sustain the needs of their internal environments

As organisms grow, the size of their cells do not increase they simply divide into more cells!

Cells need a high surface area to volume ratioREMEMBER: Cell membrane lets things in (like

glucose) and removes others (carbon dioxide) Very large cells cannot let things in and out fast

enough to maintain the needs of the larger cell

ANSWER: Cells divide after growth or die because eventually they cannot sustain the needs of their internal environments

MitosisMitosisThe multi-

step process of cell division in the cell cycle is called mitosis.

The multi-step process of cell division in the cell cycle is called mitosis.

What is the purpose of Mitosis?What is the purpose of Mitosis?

1. Maintain a high surface area to volume ratio when cells grow.

2. Reproduction (When unicellular organisms go through mitosis there are now two identical organisms.)

3. Multicellular organisms go through mitosis to:

1. produce new cells to grow (bone cells)

2. replace damaged or dying cells (blood cells)

1. Maintain a high surface area to volume ratio when cells grow.

2. Reproduction (When unicellular organisms go through mitosis there are now two identical organisms.)

3. Multicellular organisms go through mitosis to:

1. produce new cells to grow (bone cells)

2. replace damaged or dying cells (blood cells)

Mitosis overviewMitosis overviewProduces two identical cellsEach cell has a full set of

DNA (diploid – two sets for each gene)

Stages of Mitosis:ProphaseMetaphaseAnaphaseTelophase

Produces two identical cellsEach cell has a full set of

DNA (diploid – two sets for each gene)

Stages of Mitosis:ProphaseMetaphaseAnaphaseTelophase

Which cells are undergoing mitosis?

Prophase (early)Prophase (early)Chromosomes shorten and thickenNuclear membrane disappears

Chromosomes shorten and thickenNuclear membrane disappears

Prophase (late)Prophase (late) Spindle fibers formed from microtubules Microtubules surround centromere Chromosomes begin to move

Spindle fibers formed from microtubules Microtubules surround centromere Chromosomes begin to move

MetaphaseMetaphasePairs of sister chromatids align at

center (middle/metaphase)Forms metaphase plate

Pairs of sister chromatids align at center (middle/metaphase)Forms metaphase plate

AnaphaseAnaphaseChromatids separate at centromereChromatids pulled apart in opposite

directions toward polesEqually divides DNA

Chromatids separate at centromereChromatids pulled apart in opposite

directions toward polesEqually divides DNA

TelophaseTelophaseCell cytoplasm readied for divisionSpindle fibers disassemble2 Nuclear envelopes reformCytokinesis occurs

Cell cytoplasm readied for divisionSpindle fibers disassemble2 Nuclear envelopes reformCytokinesis occurs

Cytokinesis (part of telophase)Cytokinesis (part of telophase)

Division of cytoplasm and organelles to create 2 new identical cells.

--Includes the construction of cell membrane between two new cells

--Process differs in animals and plant cells

Division of cytoplasm and organelles to create 2 new identical cells.

--Includes the construction of cell membrane between two new cells

--Process differs in animals and plant cells

AnimalAnimalCell pinched in twoPinching at cleavage

furrow

Cell pinched in twoPinching at cleavage

furrow

• New cell wall must be laid down• Cell plate forms

Plant