Unit 5 Part BCell Growth, Division

and Reproduction

Cell Size Are whale cells the same size

as sea stars cells?

Yes!

Cell Size Limitations• Cells that are too big will have difficulty diffusing

materials through the cell.

- Nutrients, water, and air must enter cell at an efficient rate and cells need to remove wastesfrom the cell quickly or else they will build up toxins

• Cytoskeleton cannot support the cell organelles

• Cellular communication decreases and is less efficient

• DNA will a limit a cell’s size

– If cell is too big then DNA cannot make enough proteins to support the cell

It takes moretime for the nutrients to reach the

center of this cell

Large Cell

It takes lesstime for the same nutrients to reach the center of this cell

Smaller cell

Cellular GrowthCopyright © McGraw-Hill Education

Cell Size Limitations

Ratio of surface area to volume

Works

Better

How do cells solve this problem?

As cell size increases too much- it can

lead to death of a cell.

It is important for cells to stay small so

it can function properly by

transporting materials in & out faster.

ANSWER: Cells divide before they

get too big!

CELL CYCLEIS THE SERIES OF EVENTS THAT TAKE PLACE IN A CELLLEADING TO ITS DIVISION AND DUPLICATION(REPLICATION) THAT PRODUCES TWO DAUGHTER CELLS.

G0

The Cell Cycle

Eukaryotic cells divide via

the cell cycle.

Prokaryotic cells divide via

binary fission.

9

Cell Division in Prokaryotes (No Nucleus)

Cell Division in Prokaryotes

Prokaryotes such as bacteria divide by theasexual process of binary fission

Parent cell

2 identical daughter cells

Chromosome doubles

Cell splits

Binary Fission

11

Advantages for prokaryotes:

• Only requires a single organism to start

• Reproduce quickly and increase in population.

• Less energy usage

Disadvantages:

• All new cells are clones (identical) so the only

source of genetic variation is mutation

The Cell Cycle Process by which a cell

grows and divides toproduce IDENTICAL newcells

All cells go through cell division.

Cells divide before they become too big

Average cycle for a cell is 22 hours.

Cells grow and divide

SO that YOU can grow and reproduce

Human life

cycle

includes

is divided into is divided into

What are the TWO main phases of the cell cycle?

Cell Cycle

MitosisInterphase

G1 phase S phase ProphaseG2 phase Metaphase TelophaseAnaphase

G0 phase

Interphase: LONGEST (90%) phase of the cell cycle (G1 , G0 , S, G2 Phase)

Interphase: G1

1st growth

cell increases size

carries out normal life

activities

Ribosomes makes

proteins

Cell Cycle Phases: G0 G O Phase

Resting phase

No division

Some cells never

leave G O phase

ex. Nerve cells (once it’s

gone- it’s gone)

Some cells never

enter G O phase

ex. Skin cells

(constantly renewed)

G0

Interphase: S – DNA Synthesis

DNA Replication – process

by which DNA is copied

to make 2 identical DNA

molecules.

Double the amount of

chromosomes in cell(you must give new cells a copy of ALL the

instructions)

Interphase: G2G2 phase:

The 2nd growth

Cell prepares to divide

(mitosis)

cell’s organelles are

reproducedex. Mitochondria, vacuole, golgi,

chloroplast

Needed proteins are

produced to build.

Not a part of Interphase

Mitosis –Division of Cell Nucleus

Cytokinesis- Division on the Cytoplasm (2 new cells)

WHERE HAVE SCIENTISTS BEEN?A BRIEF HISTORY

Oswald Avery (1944) Discovered that the

nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next

ERWIN CHARGAFF (1950)

Discovered a relationship in the nitrogenous bases

Adenine (A) = Thymine (T)

Guanine (G) = Cytosine (C)

ALFRED HERSHEY & MARTHA CHASE (1952)

Concluded that the genetic material of the bacteriophage was DNA, not protein.

Used radioactive phosphorous and sulfur.

ROSALIND FRANKLIN (1952)

Took an x-ray of the DNA structure so the patterns could be seen.

The x-rays show that DNA is twisted around each other like a helix and has two strands.

(1953)Watson and Crick proposed that DNA is made up of 2 chains of nucleotides held together

by nitrogenous bases & that the 2 strands are twisted together in a shape called a double helix.

Deoxyribonucleic Acid (DNA)

Words related to DNA:

Nucleic Acids

Chromosome

Chromatin

Chromosomal

Genetic material

Hereditary information

Genes

Alleles

Function of DNA:The master copy of an organism’s information

code that contains the instructions (blueprint) used to make proteins

Determines how an organism looks and acts(traits)

Protein

Coiled (twisted) DNA

Gene

Trait

DNA StructureA gene is a section of DNA that codes for a

protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us different physical traits .

DNA StructureDeoxyriboNucleic Acid

The DNA shape looks like a twisted ladder and is called a Double Helix.

DNA is a polymer made up of millions of tiny monomers (subunits) called nucleotides.

Each nucleotide has 3 parts:1. Phosphate group2. Deoxyribose sugar3. 1 of 4 Nitrogenous bases

Draw and Label a nucleotide.

Phosphate

DeoxyriboseSugar

NitrogenousBase

Nucleotides

The phosphate (P) and deoxyribose sugar (S) form the outside of the DNA molecule.

S P S P S P S P S P S P S P S P S P S

P S P S P S P S P S P S P S P S P S P S

N N N N N N N N N N

Nucleotides

The nitrogenous bases form the inside of the DNA molecule.

There are four types of nitrogenous bases.

S P S P S P S P S P S P S P S P S P S

P S P S P S P S P S P S P S P S P S P S

N N N N N N N N N N

Nucleotides

A

Adenine (Purine)

T

Thymine (Pyrimidine)

G

Guanine(Purine)

C

Cytosine(Pyrimidine)

Nucleotides Each base will only bond with one other specific

base held together with hydrogen bonds.

Adenine (A)

Thymine (T)

A = T

Cytosine (C)

Guanine (G)

C = G

Form a base pair.

Form a base pair.

If there are 5 A’s, how many T’s are

there?___________5

If there are 82 G’s, how many C’s

are there?________82

Because of the

hydrogen bonds,

Adenine can only

bond with Thymine

& Guanine can only

bond with Cytosine

*A purine is always paired with a

pyrimidine.

Thymine

Adenine

Cytosine

Guanine

This is known as

COMPLEMENTARY base pairing

G

G

A

T

T

A

A

C

T

G

C

A

T

C

DNA StructureBecause of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

A G G - C T C - A A G - T C C - T A G

T C C - G A G - T T C - A G G - A T C

DNA VIDEO: what is it and how does it work

DNA Replication (to copy) DNA has to be copied before new

cells can be made in cell division.

DNA Replication happens during the S phase or synthesis phase of the cell cycle

All new cells have to

be given a complete

set of DNA instructions!

Without replication, new cells would NOT have a complete set of DNA instructions & the organism would not function.

DNA ReplicationReplication is semi-conservative (one strand

is old, one strand new)

This is to help prevent mistakes (mutations) in DNA.

Think* You want to copy of Mickey Mouse. Is it easier to draw or trace?

Semi-Conservative= Tracing!

General Process of DNA ReplicationStep 1: Separation of strands.

DNA has to unwind and unzip.

DNA separates in the middle (weak hydrogen bonds).

Helicase is the enzyme speeds the breaking of hydrogen bonds.

Step 2: Base pairing & Bonding of bases

The free floating bases in the cytoplasm will attach to bases to the exposed DNA.

Step 2: Base pairing & bonding

Remember bases bond A=T , C=G.

Free nucleotides continue to pair up until the entire double strand of DNA has been copied

DNA polymerase is the enzyme that builds and joins the nucleotides

DNA is made out of an original strand with a new strand. This is called semi-conservative.

Step 3: Results of replication.

Replication produces 2 IDENTICAL molecules

of DNA. The polymers will twist back up. Now

new daughter cells can be made!

Video

Whew- end of S phase

BACK TO THE CELL CYCLE!!!

Mitosis and Cytokinesis

Mitosis OverviewShortest phase of Cell Cycle

A eukaryotic cell divides to produce two daughter cells that are genetically identical to the parent cell.

Daughter cells have the SAME number of chromosomes as the parent cell

Parent cell

Mitosis – is divided into 4 phases

1) Prophase

2) Metaphase

3) Anaphase

4) Telophase

Prophase PREPARE

Centrioles move to the opposite sides

Spindle fibers form

Visible chromatids (DNA)

Nuclear envelope breaks down

Sister Chromatids are held

together by a Centromere

Metaphase MIDDLE

The sister chromatids line up across the

MIDDLE (equator) of the cell

*no more nucleus

Sister chromatids is connected to a spindle

fiber at its centromere.

Anaphase AWAY

Sister chromatids separate and move

AWAY from each other.

What happens if the chromatids break? Mutations!

Telophase TWO

The chromosomes move to opposite sides of

the cell .

Two new nuclear membranes will form

around the sets of chromosomes.

*nucleus reforms in each cell

MITOSIS IS OVER!*remember only PMAT for mitosis

M-Phase continues with CYTOKINESIS

Cytokinesis CUT

Cell membrane CUTS

inward to create 2 cells

Each cell has its own

nucleus with identical

chromosomes

CYTOKINESIS IN PLANT CELLS

Cell plate forms prior to the cell wall

appearing

MitosisLet's watch the whole process now.

Source: http://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf

*many of these stages overlap when occurring –

constant process

Identify the different stages of the cell cycle:

I Passed My Algebra Test Corrections

•Interphase

•Prophase

•Metaphase

•Anaphase

•Telophase

•Cytokinesis

(Two Identical Daughter Cells)

(New Cell)

PUT in ALL together: Cell Cycle

MITOSIS (ASEXUAL) Video- stop at 4:03

Parent Cell has 4 chromosomes

Chromosomes replicate = 8

chromosomes

Cell divides producing 2 identical

daughter cells each with

4 chromosomes

EUKARYOTIC REPRODUCTIONMITOSIS (ASEXUAL)

If the Parent Cell has 16

chromosomes instead of 4

How many chromosomes would

you have after replication?

How many chromosomes would

each Daughter Cell have?

32 chromosomes

16 chromosomes

CELL CYCLE: WHAT STAGE OF INTERPHASE IS A?WHAT STAGE IS B?

Video Review Amoeba sisters: Mitosis

Regulating the Cell Cycle

Cell growth and cell division are carefully

controlled inside an organism.

Most nerve and muscle cells do not divide once

they have developed (G0 phase)

Cells that make blood, skin, and hair divide

rapidly throughout life

Regulating the Cell CycleCell division is controlled by:

Cyclins regulates timing of cell division

Regulator Proteins including growth factors

Apoptosis: when a cell is programmed to die

What happens if cell division is NOT regulated???

Cell Cycle Disorder: CANCER Cancer - the uncontrolled division (mitosis) of

cells (cells can’t stop making more cells; divides

rapidly)

Due to mutation in DNA

Cells lose the ability to control their growth rate

Cells no longer respond to signals that regulate

growth of most cells.

Cell Cycle Disorder: CANCER Cancer cells form masses of cells called tumors and

cause damage to other cells and tissues

a. Benign tumor: does not spread to surrounding

healthy tissue

b. Malignant tumor: invade and destroy other tissue

(*move)

Tumor in liver

Causes of Cancer

• Surgery

• Radiation

• Chemotherapy

Treatment of Cancer

• Smoking

• Radiation exposure

• Defective genes

• Viral infections

Cell cycle and Cancer Amoeba SISTERS: Cell Cycle and Cancer