Lesson Overview Lesson Overview Regulating the Cell Cycle Lesson Overview 10.1 Cell Growth, Division, and Reproduction

Lesson Overview Regulating the Cell Cycle

Lesson Overview10.1 Cell Growth, Division,

and Reproduction


Limits to Cell Size

• What are some of the difficulties a cell faces as it increases in size?

• The larger a cell becomes, the more demands the cell places on its DNA.

• A larger cell is less efficient in moving materials.


Information “Overload”

Living cells store critical information in DNA.

As a cell grows, more information is needed.

If a cell were to grow too mcuh, an “information crisis” would occur.


Information “Overload”

Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access.

A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to help the growing cell.


Exchanging Materials

• Material move in and out based on the cell’s surface area.

• The rate at which materials are used up depends on the cell’s volume.

• The ratio of surface area to volume is key to understanding why cells must divide as they grow.


Ratio of Surface Area to Volume

-Imagine a cell shaped like a cube.

-As the length increases, its volume increases faster than its surface area. • The SA:V ratio decreases.


Traffic Problems

• Compare to a town – As the town grows, it becomes more difficult to move information and goods.

Similarly, a cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.


Division of the Cell

Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division.

Cell division keeps a stable SA:V ratio.


Cell Division and Reproduction

How do asexual and sexual reproduction compare?

-Asexual reproduction – Produce genetically identical offspring from a single parent


-Sexual reproduction – Offspring inherit some of their genetic information from each parent.


Asexual Reproduction

• Advantages:• Quick, produces many.

• Disadvantages• Genetically identical / no diversity


Sexual Reproduction

• Advantages:• Genetic diversity

• Disadvantages:• Time, less produced


Review

1. What are two reasons a large cell is problematic?-Too much demand on DNA-Less efficient at moving materials

2. What ratio decreases as a cell gets larger?-SA:V


Review

3. How many parents are involved in asexual reprod?-One

4. How do offspring compare to the parent in A.R.?-They are identical

5. How many parents are involved in sexual reprod?-Two

6. How do offspring compare to the parent in S.R.?-Mix of genes


Review

7. Fill in the information below:-Sexual Reproduction

-Advantage:-Genetic Diversity

-Disadvantage-Takes time


Review

8. Fill in the information below:-Asexual Reproduction

-Advantage:-Quick and many produced

-Disadvantage-No diversity


Lesson Overview10.2 The Process

of Cell Division


Prokaryotes

• Cells carry genetic information in packages of DNA called chromosomes.

• Most prokaryotes have only one circular stand of DNA


Eukaryotes• In eukaryotes, the DNA is wound around a

histone protein • Together make a nucleosome.• Chromosomes make the precise

separation of DNA during cell division.


DNA is condensed to form chromatin, which condense even more to form chromatids, which make up chromosomes.


The Prokaryotic Cell Cycle

• In prokaryotes, cells go through a process of cell division known as binary fission.

• Binary fission = asexual reprod. = Identical offspring


The Eukaryotic Cell Cycle

Interphase • The time

betweencell divisions.

• Period of growth that consists of the G1, S, and G2 phases.


1.

2.3.

4.


Interphase

• G1 phase – cells get larger and make new materials.

• S (synthesis) phase – new DNA is synthesized

• G2 phase - prepare for cell division


M Phase: Cell Division

• In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.

• Mitosis - division of nucleus.

• Cytokinesis – division cytoplasm.


Mitosis

Cytokinesis


Review1. How many strands of DNA do prokaryotes have?

- One2. Nucleosomes are made up of what two things?

-DNA wound around a histone protein3. Organize “chromatid, chromosomes, DNA, and

chromatin” in order from smallest to largest.-DNA, chromatin, chromatid, chromosome

4. Prokaryotes go thorugh a process of asex. reprod. called…

- Binary Fission


Review5. What are the four phases of the cycle cycle?

- G1, S, G2, M6. G1, S, and G2 phases are all part of what?

-Interphase 7. What two phases make up the M Phase?

- Mitosis and Cytokinesis8. What’s the difference between mitosis and cytok.?

-Mitosis – Nucleus splits-Cytokinesis – Cytoplasm splits


Important Cell Structures Involved in Mitosis

Chromatid – each strand of a duplicated chromosome

Centromere – the area where chromatids are joined


Important Cell Structures Involved in Mitosis

Centrioles – organize the spindle

Spindle – come from centrioles, separate the chromatids


Four Steps of Mitosis:

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase


1. Prophase

• Prophase -first phase of mitosis-chromosomes condense and becomes visible.

• Centrioles move to opposite sides of nucleu

• The nucleolus disappears and nuclear envelope breaks down.


2. Metaphase

Metaphase, -second phase of mitosis-centromeres line up across the center.

A spindle fiber from each pole connects to the centromere.


3. Anaphase

• Anaphase -third phase of mitosis-centromeres are pulled apart and each chromatid becomes a separate chromosome.

• The chromosomes move towards the poles.


4. Telophase

• Telophase,-fourth and final phase of mitosis-chromosomes unwind into chromatin.

• Nuclear envelope re-forms around chromosomes.

• Spindle breaks apart, and the nucleolus becomes visible in each daughter nucleus.


Cytokinesis

• Not part of mitosis!

• Part of the M Phase

• Cytokinesis completes the process of cell division – it splits one cell into two.


Cytokinesis – Animals vs. Plants

• Animals • Cell membrane is drawn in until the cytoplasm

is pinched into two equal parts.


Cytokinesis – Animals vs. Plants

• Plants• In plants, the cell wall prevents pinching.• Instead, a cell plate forms between

nuclei and becomes a cell wall.


The Stages of the Cell Cycle


Review

1. The chromatids are joined at the -Centromere

2. The spindle is organized by what structures?- Centrioles

3. Think of a mnemonic for the 4 stages of mitosis.-Please Make A Take

4. Cytokinesis is not part of…-Mitosis


Review

5. Which part of mitosis do chromatids line in the middle?-Metaphase

6. What part does the chromosomes become visible?-Prophase

7. What part does the nuclear envelope start to reform?-Telophase

8. What part pulls the sister chromatid apart?-Anaphase


Lesson Overview10.3 Regulating

the Cell Cycle


• Controls on cell growth and division can be turned on and off.

• For example, when an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process. The rate of cell division slows when the healing process nears completion.

The Cell Cycle


The Discovery of Cyclins

• Cyclins - proteins that regulate the cell cycle in eukaryotic cells.

• This graph shows how cyclin levels change throughout the cell cycle in fertilized clam eggs.


Regulatory Proteins

• Internal regulators - respond to events inside a cell. • Allow the cell cycle to proceed only once certain

processes have happened.

• External regulators - respond to events outside the cell. • Direct cells to speed up or slow down the cell cycle.• Ex - Growth factors –

Important during embryonic development and wound healing.


Apoptosis

• Apoptosis - programmed cell death.• Plays role in shaping structure. • For example, the foot of a mouse is shaped the way it is

partly because the toes undergo apoptosis during tissue development.

http://www.youtube.com/watch?v=9KTDz-ZisZ0


• Cancer - disorder in which body cells lose ability to control cell growth.

• Cancer cells divide uncontrollably to form a mass of cells called a tumor.

Cancer and the Cell Cycle


• Benign tumor = noncancerous.

Does not spread to surrounding healthy tissue.

• Malignant tumor = cancerous.It spread and destroys surrounding healthy tissue.

Cancer and the Cell Cycle


What Causes Cancer?

• Caused by defects in genes that regulate cell growth and division.

• Causes include smoking tobacco, radiation exposure, defective genes, and viral infection.

• A damaged p53 gene is common in cancer cells. • Causes cells to lose the information needed to

respond to growth signals.


Treatments for Cancer

• Some localized tumors can be removed by surgery.

• Many tumors can be treated with targeted radiation.

• Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

• Cancer Warrior PBS

http://www.pbs.org/wgbh/nova/body/cancer-warrior.html


Review

1. When might cell growth be stimulated?- Injury, growth, etc.

2. Which protein regulates the cell cycle in eukar.?- Cyclin

3. Which regulator would prevent anaphase from happening before prophase?

- Internal regulators4. What is an example of an external regulator?

-Growth factor


Review

5. What is apoptosis?- Programmed cell death

6. During cancer, cells lose the ability to…-Control cell growth

7. What type of tumor is noncancerous?- Benign

8. Which damaged gene is commonly found in cancer cells?

- p 53


10.4 Cell Differentiation


• All organisms start a single cell.

• Embryo - Early stage of development

• During development, an organism’s cells become differentiated and specialized for particular functions.

From One Cell to Many


Defining Differentiation• Differentiation - process by which cells become

specialized.• Cells differentiate into many different types and become

specialized to perform certain tasks.


Human Development

• Totipotent - able to become everything (a fertilized egg)

• After a few days, a human embryo forms into a blastocyst, a hollow ball of cells with a cluster of cells inside known as the inner cell mass.

• The inner cell mass are pluripotent – can become many, but not all, of the body's cell types.


Stem Cells

Stem cells are unspecialized cells from which differentiated cells develop.

http://www.pbs.org/wgbh/nova/body/stem-cells-breakthrough.html


Embryonic Stem Cells

• Embryonic stem cells – found in the inner cells mass.

• Embryonic stem cell are pluripotent.

http://www.youtube.com/watch?v=mUcE1Y_bOQE


Adult Stem Cells

• Adult organisms contain certain stem cells.

• Adult stem cells are multipotent – produce a few types of differentiated cells.

• Adult stem cells of a given organ or tissue typically produce only the types of cells that are unique to that tissue.


Potential Benefits

• Stem cell research may lead to new ways to repair the cellular damage that results from heart attack, stroke, and spinal cord injuries.


Ethical Issues• Most techniques for gathering

embryonic stem cells destroy the embryo.

• Groups seeking to protect embryos oppose such research as unethical. Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.

• BBC Documentary

http://www.youtube.com/watch?v=iaejq2ohClU&feature=results_main&playnext=1&list=PL3FD3D77C067F0C3E


Review

1. What is the earliest stage of development called?- Embryo

2. The process by which cells become specialized is…

- Differentiation

3. What is totipotent, pluripotent, and multipotent?

-Totipotent – can become all cells

-Pluripotent – can become most cells

-Multipotent – can become few cells


Review

4. Stem cells are cells.-Undifferentiated

5. Adult stem cells produce cells that are…-Unique to that tissue

6. Why is stem cell research important?-Repair damaged cells and save lives

7. Why is stem cell research controversial?-Save embryos vs. save lives

Documents

Lesson Overview Lesson Overview Regulating the Cell Cycle Lesson Overview 10.1 Cell Growth, Division, and Reproduction