Cell Division Ch. 9 Biology Moore High School 2015 OBJECTIVES TO ANSWER: WHY AREN’T ALL LIVING THINGS ONE-CELLED? WHAT CAUSES A CELL TO DIVIDE? HOW DOES THE PROCESS OF CELL DIVISION WORK?

Cell Division is Miraculous Watch this videovideo

Cell Size Limitations Why are most cells so small? Factors that influence cell size 1.Ratio of surface area to volume 2.Transport of substances must be efficient and quick 3.Cellular communications need to be quick

Ratio of surface area to volume

Once the volume of the CELL gets so large and the plasma membrane is stretched to its limits it no longer is efficient.

All of these Gel cubes were left in solution the same amount Of time but the dye moved all the way through the small cube. WHY? LESS VOLUME FOR THE CELL SO IT COULD MOVE EFFICIENTLY THROUGH

So Why are Cells so Small? Watch this video Watch this videovideo

The Cell Cycle

The stages of Interphase The CELL CYCLE IS DIVIDED INTO: Interphase, Mitosis and Cytokinesis Interphase is also divided into 3 phases: Interphase is also divided into 3 phases: G1, S and G2 Interphase is the LONGEST TIME PERIOD of the cell cycle because everything is replicating and getting ready to divide Interphase is the LONGEST TIME PERIOD of the cell cycle because everything is replicating and getting ready to divide

Mitosis and Cytokinesis Mitosis – the cell’s nuclear material divides and separates into opposite ends of the cell. It is divided into: Prophase, Metaphase, Anaphase and Telophase Cytokinesis – the cell divides into two daughter cells with identical nuclei

Prophase Prophase is the first and longest phase of mitosis. The centrioles separate and take up positions on opposite sides of the nucleus.

Prophase The centrioles lie in a region called the centrosome. The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.

Prophase Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down.

Chromosomes Each chromosome consists of two identical “sister” chromatids. Each pair of chromatids is attached at an area called the centromere. Copyright Pearson Prentice Hall

Chromosomes When the cell divides, the chromatids separate. Each new cell gets one chromatid. Copyright Pearson Prentice Hall

Metaphase Centrosomes at opposite poles of cell The chromosomes line up across the center of the cell. Centromeres of all chromosomes are aligned with one another, and sister chromatids straddle metaphase plate Microtubules connect the centromere of each chromosome to the poles of the spindle. Mitotic spindle completely formed

Anaphase The sister chromatids separate into individual chromosomes. The chromosomes continue to move until they have separated into two groups.

Telophase and Cytokinesis Daughter nuclei form at two poles of cell A new nuclear envelope forms around each cluster of chromosomes. Chromosomes gather at opposite ends of the cell and uncoil back into chromatin Mitotic spindle disappears Nucleolus reforms

Cytokinesis During cytokinesis, the cytoplasm pinches in half. Process overlaps with telophase of mitosis Each daughter cell has an identical set of duplicate chromosomes Copyright Pearson Prentice Hall

Cytokinesis Figure 8.9bFigure 8.9a

Cytokinesis Occurs differently in plants and animals – Cleavage furrow forms in animal cells – Cell plate forms in plant cells Cleavage furrow Cell Plate

Let’s watch the Cell Cycle Cell CycleCell Cycle

Prokaryotes Bacterial cells and some unicellular organisms divide by binary fission

Cell Division Compared Mitosis – Eukaryotic Cells Ensures proper division of the nucleus and chromosomes using spindle fibers, PMAT Binary Fission – Prokaryotic Cells Uses the plasma membrane to make sure the DNA is correctly copied

Binary Fission Before dividing, an exact copy of the chromosome is made The attachment point divides so the 2 new chromosomes are attached at separate parts of the membrane The cell elongates and a new plasma membrane is added and the attachment points move apart The plasma membrane and new cell wall pinch through the cell, separating the 2 chromosomes into two new, identical cells Copyright © 2001 Pearson Education, Inc. publishing Benjamin Cummings

9.2 Section Summary Mitosis is the process by which the duplicated DNA is divided The stages of mitosis include prophase, metaphase, anaphase, and telophase Cytokinesis is the process of cytoplasm division that results in genetically identical daughter cells

1.Replacement of lost or damaged cells 2.Growth—multicellular organisms grow and develop from single cell (fertilize egg) 3.Cell Reproduction Functions of Cell Divsion

Cell Division

Copyright Pearson Prentice Hall The series of events that cells go through as they grow and divide is called a)the cell cycle. b)mitosis. c)interphase. d)cytokinesis.

Copyright Pearson Prentice Hall The phase of mitosis during which the chromosomes line up across the center of the cell is a)prophase. b)metaphase. c)anaphase. d)telophase.

Copyright Pearson Prentice Hall Cytokinesis usually occurs a)at the same time as telophase. b)after telophase. c)during interphase. d)during anaphase

Copyright Pearson Prentice Hall DNA replication takes place during the a)G 2 phase of the cell cycle. b)G 1 phase of the cell cycle. c)S phase of the cell cycle. d)M phase of the cell cycle.

Copyright Pearson Prentice Hall During mitosis, “sister” chromatids separate from one another during a)telophase. b)interphase. c)anaphase. d)metaphase.

END OF SECTION

Cell Cycle Regulation Ch. 10 Biology Ms. Haut

9.3 Cell Cycle Regulation Objectives –Summarize the role of cyclin proteins in controlling the cell cycle. –Explain how cancer relates to the cell cycle. –Describe the role of apoptosis. –Summarize the two types of stem cells and their potential uses. Review Vocabulary –Nucleotide-subunit that makes up DNA and RNA molecules

9.3 Cell Cycle Regulation New Vocabulary –Cyclin –Cyclin-dependent kinase –Cancer –Carcinogen –Apoptosis –Stem cell Main idea –The normal cell cycle is regulated by cyclin proteins.

Controls on Cell Division Experiments show that normal cells will reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing. This demonstrates that controls on cell growth and division can be turned on and off. Copyright Pearson Prentice Hall

Controls on Cell Division Contact Inhibition Cells attach to dish surface and divide. When cells have formed a complete single layer, they stop dividing (contact inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (contact inhibition).

Normal Cell Cycle Different cyclin/cyclin- dependent kinase (CDK) combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle

Quality Control Checkpoints The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong. Spindle checkpoints also have been identified in mitosis

Abnormal Cell Cycle: Cancer Cancer is the uncontrolled growth and division of cells Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Causes of Cancer The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations Various environmental factors, such as, asbestos, tobacco products, ultraviolet radiation and X-rays can affect the occurrence of cancer cells.

Apoptosis Programmed cell death Cells going through apoptosis actually shrink and shrivel in a controlled process Apoptosis can help to protect organisms from developing cancerous growths

Stem Cells Unspecialized cells that can develop into specialized cells when under the right conditions

Stem Cells Embryonic Stem Cells – After fertilization, the resulting mass of cells divides repeatedly until there are about cells. These cells have not become specialized. Adult Stem Cells – Found in various tissues in the body and might be used to maintain and repair the same kind of tissue – Less controversial because the adult stem cells can be obtained with the consent of their donor

9.3 Summary The cell cycle of eukaryotic cells is regulated by cyclins Checkpoints occur during most of the stages of the cell cycle to ensure that the cell divides accurately Cancer is the uncontrolled growth and division of cells Apoptosis is a programmed cell death Stem cells are unspecialized cells that can develop into specialized cells with the proper signals

Cell Cycle Regulators The cell cycle is regulated by a specific protein. The amount of this protein in the cell rises and falls in time with the cell cycle. Scientists called this protein cyclin because it seemed to regulate the cell cycle. Cyclins regulate the timing of the cell cycle in eukaryotic cells. Copyright Pearson Prentice Hall

Internal Regulators Proteins that respond to events inside the cell are called internal regulators. Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell. – Cells do not enter into Mitosis until all chromosomes have been copied – Anaphase does not occur until all chromosomes are lined up on metaphase plate and attached to the mitotic spindle Copyright Pearson Prentice Hall

External Regulators Proteins that respond to events outside the cell are called external regulators. External regulators direct cells to speed up or slow down the cell cycle.

External Regulators Growth factors are proteins that stimulate growth and division After forming a single layer, cells have stopped dividing. Providing an additional supply of growth factors stimulates further cell division.

External Regulators Other molecules found on the surfaces of neighboring cells can slow down or stop their cell division – Prevents excessive cell growth and keeps tissues in the body from disrupting one another

Uncontrolled Cell Growth Cancer is a disorder in which some of the body's own cells lose the ability to control growth. Cancer cells do not respond to the signals that regulate the growth of most cells. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Uncontrolled Cell Growth Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death. w.mmshealthyforlife.com/wp- content/uploads/2009/04/cancer_cells_splitting.jpg&i mgrefurl=

Uncontrolled Cell Growth Two types of tumors – Benign tumors Grow only locally Do not spread Can typically be removed – Malignant tumors Grow and invade neighboring tissues Can break away from original tumor and spread throughout the body (metastasis)

Uncontrolled Cell Growth An astonishing number of cancer cells have a defect in a gene called p53 p53 is a tumor suppressing gene found on chromosome 17 – Prevents mitosis if DNA is damaged – Will activate other genes to stop cell growth or cause cell death

Risks of Cancer Tobacco (lung cancer, lip and mouth cancer) Sunlight (UV radiation leading to skin cancer) Ionizing radiation (X-rays) Certain chemicals and other substances (asbestos, benzene, certain metals, etc.) Some viruses and bacteria (liver cancer, lymphoma, leukemia) Alcohol (liver cancer, breast cancer) Poor diet, lack of physical activity, or being overweight Growing older Family history of cancer www. cancer.gov

Cell Cycle Regulation

Copyright Pearson Prentice Hall The cell cycle is believed to be controlled by proteins called a)spindles. b)cyclins. c)regulators. d)centrosomes.

Copyright Pearson Prentice Hall Proteins that respond to events inside the cell are called a)internal regulators. b)external regulators. c)cyclins. d)growth factors.

Copyright Pearson Prentice Hall One of the functions of internal regulators is to a)cause the cell to stop dividing. b)prevent anaphase from occurring until all chromosomes are attached to the spindle. c)trigger cancer formation. d)undergo cell division randomly.

Copyright Pearson Prentice Hall One effect of an internal regulator is that a cell will not begin mitosis until a)it becomes too large. b)the cell’s growth is stimulated. c)it is in physical contact with other cells. d)all its chromosomes have been replicated.

Copyright Pearson Prentice Hall One factor common to almost all cancer cells is a)a lack of cyclin. b)a defect in gene p53. c)exposure to tobacco smoke. d)exposure to radiation.