Cell Growth and Division

CHAPTER 10

EQ – Why do cells grow and divide?

The adult human body produces

roughly 2 TRILLION cells every day.

DID YOU KNOW THAT …

So that the organism can grow and develop

As multicellular organisms grow larger, its cells

reproduce and increase in number.

WHY DO CELLS REPRODUCE?

Replacement of dead/damaged cells

To prevent cell overload

WHY DO CELLS REPRODUCE?

Cell size is limited by the cell membrane (surface area)

Everything must enter and leave through the cell membrane.

Compared to smaller cells, larger cells must take in more nutrients, process (break down) them, and get rid of more waste.

Too large = TRAFFIC JAM!

CELL MEMBRANE OVERLOAD

What does the work of cells?

What provides the instructions

for proteins?

Larger cells require more

proteins!

If cell get too large, DNA

cannot be copied fast enough

to make proteins.

DNA OVERLOAD

Proteins

DNA

Gene – a unit of heredity that consists of DNA

that codes for a protein

The activity of the cell is directed by the DNA

because it contains the instructions for making

proteins.

DNA OVERLOAD

Chromatin – loose and stringy DNA

Most of the time DNA exists as chromatin

because it is easier to copy the instructions for

the proteins when loose.

CHROMOSOMES OR CHROMATIN???

Chromosome –DNA tightly coiled (wrapped)

around proteins called histones

When the cell gets ready to reproduce, the chromatin

condenses into chromosomes because it is easier to move

the chromosomes when they are packed up.

CHROMOSOMES OR CHROMATIN???

What form is the DNA in when the cell is dividing?

What form is the DNA in when it is being used to

make proteins?

CHROMOSOMES OR CHROMATIN???

Chromosome

Chromatin

Chromatid – one of the two strands of a duplicated chromosome

A single long molecule of DNA

Sister chromatids – identical chromosome pairs that are still connected together

Centromere – the region of the chromosome that holds the sister chromatids together during cell division

CHROMOSOME STRUCTURE

sister chromatids

CHROMOSOME STRUCTURE

When sister chromatids

are connected, they are

considered one

chromosome.

When sister chromatids

are separated during cell

division (mitosis), they are

considered two individual

chromosomes.

Recall – All cells are

produced by the division

of preexisting cells.

The parent cell must give

each daughter cell all the

equipment it needs to

survive.

Organelles and DNA

PREPARING FOR CELL DIVISION

Once a bacterium has doubled in size, the cell will divide.

Prokaryotes copy the DNA and divide the cytoplasm.

Process called binary fission

PROKARYOTIC REPRODUCTION

CELLSALIVE.COM

Under the first box – Interactive Cell Models –

Click on PLANT/ANIMAL CELL

Click START THE ANIMATION (red box).

Follow the directions on the worksheet.

Answer the questions on notebook paper

(answers only).

CELLS ALIVE - REVIEW

Ch. 10 Sec. 2

THE EUKARYOTIC

CELL CYCLE

EQ – How does the cell prepare for division?

Cell cycle – a

repeating

sequence of

cellular growth

and division

during the life of

the cell.

EUKARYOTIC CELL CYCLE

The cell is not dividing

The cell is growing and preparing to divide

How long does interphase last?

INTERPHASE

The majority of the

cell’s life

Skin cells – short

interphase

Nerve cells – most of

life (most of your life)

Divided into 3 parts:

G1 Phase growth

S Phase DNA

synthesis

Synthesis – to make

G2 Phase Growth

and preparation for

division

INTERPHASE

Two Processes: Mitosis and Cytokinesis

During these phases, the cell’s DNA and

cytoplasm divide

Cytoplasm includes the fluid and organelles

CELL DIVISION

Carries out normal cell activities

Cell grows by building more

organelles

DNA exists as chromatin so that

it can be used to make proteins

Most of a cell’s life is spent in

this phase

Cells that do not divide remain in

this phase (G0)

Brain cells

G1 PHASE

DNA replicates (gets copied).

At the end of S, the nucleus holds twice as much DNA

DNA now exists as sister chromatids that are attached at the centromere.

S (SYNTHESIS) PHASE

Cell continues to grow and prepares to divide

Special structures (centrioles and microtubules)

that help the cell divide are assembled.

G2 PHASE

Mitosis – the process of dividing

the nucleus into two daughter

nuclei

Mitosis is divided into 4 phases:

prophase

metaphase

anaphase

telophase

At the beginning of mitosis

(prophase), the DNA is packaged

into chromosomes.

MITOSIS

Cytokinesis – the process of separating the

organelles and the cytoplasm

Occurs during telophase of mitosis.

CYTOKINESIS

Back to G1!

Start the

process

again!

WHERE DO THE NEW CELLS GO?