The Process of Cell

Growth & Division

REVIEW – What have we learned REVIEW – What have we learned so far?so far?

What makes something living?

What are the two categories of living things?

What composes a eukaryotic cell?

How does a eukaryotic cell transport materials?

Where do eukaryotic cells get energy from?

What are the different levels of organization in an eukaryotic organism? (5 levels)

How do cells progress through the different levels of organization?BY DIVIDING!

1.1. How is the life cycle of a human and a single cell similar? How is the life cycle of a human and a single cell similar? 

2.2. How is the life cycle of a human and a single cell How is the life cycle of a human and a single cell different? different? 

3.3. Compare the life of cell to the clock – in 12 hours how long Compare the life of cell to the clock – in 12 hours how long does the cell spend actually dividing? does the cell spend actually dividing? 

4.4. Why do you think cells make a copy of their DNA before Why do you think cells make a copy of their DNA before they divide in half?they divide in half?

5. What do we call DNA that is spread out?5. What do we call DNA that is spread out?

6. What do we call DNA that is coiled up?6. What do we call DNA that is coiled up?

7.7. Compare the string to DNA. Do you think it is easier for the cell Compare the string to DNA. Do you think it is easier for the cell to read (and use) the DNA when it is chromatin or chromosomes?to read (and use) the DNA when it is chromatin or chromosomes?

8.8. Compare the string to DNA. Do you think it is easier for the cell Compare the string to DNA. Do you think it is easier for the cell to pass the DNA onto future generations when it is chromatin or to pass the DNA onto future generations when it is chromatin or chromosomes? chromosomes? 

KEY

1: The prokaryotic cell before binary fission. The DNA is called chromatin.2: The DNA of the prokaryotic cell replicates.3: The DNA is pulled to the separate poles of the prokaryotic cell as it increases size to prepare for splitting.4: The growth of a new cell wall begins to separate the prokaryotic cell in half.5: The new cell wall fully develops, resulting in the complete split of the prokaryotic cell.6: The new daughter cells .

Why does the DNA have to replicate before the cell divides?

Why does the cell have to grow before it divides?

Compare the cell in #1 to the cells in #6. Are they similar, different?

• How many DIVISIONS are there in Cell Division with MITOSIS?

• How many cells result from Cell Division with MITOSIS?

• How many DIVISIONS are there in Cell Division with MIEIOSIS?

• How many cells result from Cell Division with MEIOSIS?

Cell Division with MITOSIS Cell Division with MEIOSIS Process used to reproduce Asexually Process used to reproduce Sexually How humans, grow, develop and heal How humans make their sperm or eggs Results in identical daughter cells Results in unique daughter cells Diagram of a cell with 4 chromosomes going

through Cell Division with MITOSIS Diagram of a cell with 4 chromosomes

going through Cell Division with MEIOSIS

•Read the following scenario. Label the processes (A-D) as mitosis or meiosis.

A young girl grows (A) into an adult. She produces eggs for reproduction (B). She becomes pregnant and has a baby. The baby grows (C) into a toddler.

The toddler falls and breaks her arm. Her arm heals (D).

REVIEW – What have we learned REVIEW – What have we learned so far?so far?

What makes something living?

What are the two categories of living things?

What composes a eukaryotic cell?

How does an eukaryotic cell transport materials?

Where do eukaryotic cells get energy from?

What are the different levels of organization in an eukaryotic organism? (5 levels)

How do cells progress through the different levels of organization?

Why do cells divide?Why do cells divide?

1. Repair – replacement of lost or damaged cells

2. Growth – increasing size (baby child adult)

3. Produce offspring – specie lives on to next generation

Required Reading #1: Section Required Reading #1: Section 10.110.1

1. Why do cells divide?

Repair, Growth, Produce offspring

2. How are a cell’s volume and surface area related?

Cell grows bigger = internal volume enlarges = cell membrane expands

The surface area to the volume ratio gets smaller as the cell gets larger.

Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume. When this happens, the cell must divide into smaller cells with favorable surface area/volume ratios, or cease to function.

That is why cells are so small.

How Cells DivideHow Cells Divide There are basically three ways in which cells can

divide:

Binary fission

Cell Division with mitosis

Cell Division with meiosis

Which way a cell divides depends on:

What type of cell it is

What the purpose of the division is

Prokaryotic CellsProkaryotic Cells

Remember that prokaryotic cells are small

- Also have a singular circular piece of DNA

Also remember that prokaryotic cells are always unicellular – they do not form multicellular organisms

Prokaryotic cells divided via BINARY FISSION

Here are the steps…

KEY1: Normal prokaryotic cell. The DNA is called chromatin.

Cell preparing to divide:2. DNA replicates. It begins to condense into chromosome

form.3: Cell grows (DNA segregates to opposite sides of the cell)

Cell dividing:4: A new cell wall begins divide the cell in half.5: The new cell wall fully develops. The cell divides (This

step is called cytokinesis)

6: The new daughter cell. The DNA spreads back out into chromatin.

Eukaryotic CellsEukaryotic Cells Remember that eukaryotic cells are large and complex.

Eukaryotic cells usually have multiple pieces of DNA in a rod shape (humans have 46)

Eukaryotic cells have a nucleus which traps the DNA and many other organelles

Eukaryotic cells can form unicellular OR multicellular organisms

Eukaryotic cells can divide via MITOSIS or MEIOSIS

Today we will look at MITOSIS

MitosisMitosis Mitosis is the type of division that occurs most

frequently.

This division is used to grow, develop and heal. It is also used in asexual reproduction.

Mitosis results in two identical daughter cells.

Here are the steps of the cell cycle with MITOSIS…

S phase

G1 phase

G2 phase

Growth (Interphase)Growth (Interphase) G1: Gap 1 - G1: Gap 1 - Cell Cell growsgrows bigger and bigger and

makes proteins needed for life.makes proteins needed for life.

S Phase: DNA Synthesis - S Phase: DNA Synthesis - During the S During the S phase, the cell phase, the cell replicates its DNA.replicates its DNA.

G2: Gap 2 - G2: Gap 2 - Cell Cell grows even bigger grows even bigger and makes proteins needed for two cells!and makes proteins needed for two cells!

Chromosome vs. Chromatid vs. Chromosome vs. Chromatid vs. ChromatinChromatin

Are all DNA!!

Chromosome – coiled up

Chromatin – not coiled up

Chromatid – copy of DNA attached to the original stand by the centromere.

This happens during the S Phase but DNA is still uncoiled

INTERPHASE

DNA is in chromatin form

A

Division of an Eukaryotic CellDivision of an Eukaryotic Cell There are 2 stages to Division:There are 2 stages to Division:

Division of the DNA (MITOSIS)Division of the DNA (MITOSIS)

11. Prophase. Prophase

2. Metaphase2. Metaphase

3. Anaphase3. Anaphase

4. Telophase4. Telophase

Division of the cytoplasm (CYTOKINESIS)Division of the cytoplasm (CYTOKINESIS)

VIDEO INTRODUCTIONVIDEO INTRODUCTION

P.M.A.T.

ProphaseProphase Think Prepare Think Prepare - -

The The DNA coils into DNA coils into chromosomeschromosomes..

VIDEOVIDEO

The The nucleus disappearsnucleus disappears..

Centrioles Centrioles and and spindle fibers spindle fibers take their placestake their places

Part of the cytoskeleton!Part of the cytoskeleton!

This is a picture of a cell in prophase.

MetaphaseMetaphase Think Middle Think Middle - -

Chromosomes line up at Chromosomes line up at the centerthe center of the cell. of the cell.

Centromeres become Centromeres become attached to spindle attached to spindle fibersfibers..

This is a picture of a cell in metaphase.

AnaphaseAnaphase Think - apartThink - apart

Each centromere dividesEach centromere divides. .

Sister chromatids separateSister chromatids separate and move apartand move apart..

Ever see a movie in 4D?Ever see a movie in 4D?This is a picture of a cell in anaphase.

TelophaseTelophase Think - twoThink - two

Two nuclei form Two nuclei form and the DNA and the DNA spreads back out.spreads back out.

This is a picture of a cell in telophase.

CytokinesisCytokinesis The cytoplasm The cytoplasm

divides.divides. Occurs at the same Occurs at the same

time as telophasetime as telophase..

This is a picture of a cell in cytokinesis.

Cell DivisionCell Division

Cartoon:

http://www.johnkyrk.com/mitosis.html

Computer Animation:

http://www.hybridmedicalanimation.com/anim_mitosis.html

Narration – I need a volunteer to read! Spotlighting the ballet of mitosis

Time Lapse Movie of developing sand dollar

Cell Division Cheer !Cell Division Cheer ! We are going to create a cheer! Using hand motions

to help remember the steps of the cell cycle

Your hands are going to act as the nucleus & DNA

Specifically - your fingers will represent DNA

Do cheer while watching a REAL cell divide

As the cell goes through division – say the phases in your head.

REVIEWREVIEW

What are the two types of eukaryotic cells?

PLANT

ANIMAL

What is one BIG structural difference between the two?

PLANTS – cell wall and membrane

ANIMALS – only have cell membrane

There is a difference between the cytokinesis stage in PLANT and ANIMAL cells

Cytokinesis Cytokinesis in Animal in Animal CellsCells

Cell’s membrane Cell’s membrane pinches pinches

inwardinward until the two sides until the two sides

touch resulting in two separate touch resulting in two separate

daughter cells.daughter cells.

•The pinching inward is called The pinching inward is called

the cleavage furrowthe cleavage furrow

Cytokinesis Cytokinesis in Plant in Plant CellsCellsCell’s membrane CAN NOT pinch Cell’s membrane CAN NOT pinch

inward because of the rigid cell inward because of the rigid cell

wall. Instead, awall. Instead, a cell plate cell plate

forms forms between the two nuclei between the two nuclei

and slowly grows into a new wall and slowly grows into a new wall

separating the two daughter cellsseparating the two daughter cells

CytokinesisCytokinesis

Animal –

Cell pinches inward (called cleavage furrow)

Plant -

Can not pinch because of the cell wall

Forms a cell plate

S phase

G1 phase

G2 phase

Cell Cycle in Onion CellsCell Cycle in Onion Cells

interphase prophase metaphase

anaphase Telophase / cytokinesis

Arts & Crafts Time!Arts & Crafts Time!

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