Lesson Overview Cell Growth Division and Reproduction Section

Lesson Overview Cell Growth, Division, and Reproduction Section 10. 1 CELL GROWTH, DIVISION, AND REPRODUCTION

Lesson Overview Cell Growth, Division, and Reproduction Chapter Mystery: Pet Shop Accident Julia stared into the salamander tank in horror. As an assistant in a pet shop, Julia had mistakenly put a small salamander in the same tank as a large one. Just as she realized her error, the large salamander attacked and bit off one of the small salamander’s limbs. Acting quickly, Julia scooped up the injured salamander and put it in its own tank. She was sure it would die before her shift ended. But she was wrong! Days passed…. then weeks. Every time Julia checked on the salamander, she was more amazed at what she saw. How did the salamander’s body react to losing a limb? As you read this chapter, look for clues to help you predict the salamander’s fate. Think about the cell processes that would be involved.

Lesson Overview Cell Growth, Division, and Reproduction I. Exchanging Materials a. Food, oxygen, and water enter a cell through the cell membrane b. Waste products leave in the same way c. The rate at which this exchange takes place depends on the surface area of a cell d. The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume e. The ratio of surface area to volume is key to understanding why cells must divide as they grow

Lesson Overview Cell Growth, Division, and Reproduction II. Ratio of Surface Area to Volume Imagine a cell shaped like a cube. As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume. a. If a cell gets too large, the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out.

Lesson Overview Cell Growth, Division, and Reproduction III. Division of the Cell a. Cell division: process in which a cell divides into two new “daughter cells” before it grows too large a. Before cell division the cell copies all of its DNA a. It then divides into two “daughter” cells a. each daughter cell receives a complete set of DNA – Cell division: a. reduces cell volume b. results in an increased ratio of surface area to volume for each daughter cell

Lesson Overview Cell Growth, Division, and Reproduction IV. Asexual Reproduction a. Asexual reproduction: reproduction that involves a single parent producing an offspring i. The offspring produced are, in most cases, genetically identical to the single cell that produced them ii. a simple, efficient, and effective way for an organism to produce a large number of offspring iii. both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually

Lesson Overview Cell Growth, Division, and Reproduction b. Examples of Asexual Reproduction i. Bacteria reproduce by binary fission ii. Kalanchoe plants form plantlets iii. Hydras reproduce by budding

Lesson Overview Cell Growth, Division, and Reproduction V. Sexual Reproduction a. sexual reproduction: offspring are produced by the fusion of two sex cells – one from each of two parents b. fuse into a single cell before the offspring can grow c. offspring produced inherit some genetic information from both parents d. most animals and plants, and many single-celled organisms, reproduce sexually

Lesson Overview Cell Growth, Division, and Reproduction VI. Comparing Sexual and Asexual Reproduction Fill in the table below:

Lesson Overview Cell Growth, Division, and Reproduction Mystery Clue #1 As its wound heals, the salamander’s body cells are dividing to repair the damage. In what way is this type of cell division similar to asexual reproduction?

Lesson Overview Cell Growth, Division, and Reproduction Section 10. 2 THE PROCESS OF CELL DIVISION

Lesson Overview Cell Growth, Division, and Reproduction I. Chromosomes a. The genetic information that is passed on from one generation of cells to the next is carried by chromosomes b. Every cell must copy its genetic information before cell division begins c. Each daughter cell gets its own copy of that genetic information d. Cells of every organism have a specific number of chromosomes

Lesson Overview Cell Growth, Division, and Reproduction II. Prokaryotic Chromosomes a. Prokaryotic cells lack nuclei b. Instead, their DNA molecules are found in the cytoplasm c. Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.

Lesson Overview Cell Growth, Division, and Reproduction III. Eukaryotic Chromosomes a. In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin b. Chromatin is composed of DNA and histone proteins. c. DNA coils around histone proteins to form nucleosomes d. The nucleosomes interact with one another to form coils and supercoils that make up chromosomes

Lesson Overview Cell Growth, Division, and Reproduction IV. The Prokaryotic Cell Cycle a. a regular pattern of growth, DNA replication, and cell division b. most prokaryotic cells begin to replicate, or copy, their DNA once they have grown to a certain size c. when DNA replication is complete, the cells divide through a process known as binary fission

Lesson Overview Cell Growth, Division, and Reproduction d. Binary fission: a form of asexual reproduction during which two genetically identical cells are produced e. For example, bacteria reproduce by binary fission.

Lesson Overview Cell Growth, Division, and Reproduction V. The Eukaryotic Cell Cycle a. The eukaryotic cell cycle consists of four phases: G 1, S, G 2, and M b. Interphase: the time between cell divisions i. It is a period of growth that consists of the G 1, S, and G 2 phases c. The M phase is the period of cell division.

Lesson Overview Cell Growth, Division, and Reproduction d. G 1 Phase: Cell Growth cells increase in size and synthesize new proteins and organelles

Lesson Overview Cell Growth, Division, and Reproduction e. S Phase: DNA Replication new DNA is synthesized when the chromosomes are replicated

Lesson Overview Cell Growth, Division, and Reproduction f. G 2 Phase: Preparing for Cell Division many of the organelles and molecules required for cell division are produced

Lesson Overview Cell Growth, Division, and Reproduction g. M Phase: Cell Division i. In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis. ii. Mitosis is the division of the cell nucleus. iii. Cytokinesis is the division of the cytoplasm.

Lesson Overview Cell Growth, Division, and Reproduction h. Important Cell Structures Involved in Mitosis i. Chromatid – each strand of a duplicated chromosome ii. Centromere – the area where each pair of chromatids is joined iii. Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle iv. Spindle – a fanlike microtubule structure that helps separate the chromatids

Lesson Overview Cell Growth, Division, and Reproduction VI. Prophase a. the first phase of mitosis b. the duplicated chromosome condenses and becomes visible c. centrioles move to opposite sides of nucleus and help organize the spindle d. spindle forms and DNA strands attach at a point called their centromere e. The nucleolus disappears and nuclear envelope breaks down

Lesson Overview Cell Growth, Division, and Reproduction VII. Metaphase a. the centromeres of the duplicated chromosomes line up across the center of the cell b. the spindle fibers connect the centromere of each chromosome to the two poles of the spindle

Lesson Overview Cell Growth, Division, and Reproduction VIII. Anaphase a. the centromeres are pulled apart and the chromatids separate to become individual chromosomes b. the chromosomes separate into two groups near the poles of the spindle

Lesson Overview Cell Growth, Division, and Reproduction IX. Telophase a. the chromosomes spread out into a tangle of chromatin b. a nuclear envelope reforms around each cluster of chromosomes c. the spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus

Lesson Overview Cell Growth, Division, and Reproduction X. Cytokinesis a. Cytokinesis: the division of the cytoplasm b. The process of cytokinesis is different in animal and plant cells�

Lesson Overview Cell Growth, Division, and Reproduction c. Cytokinesis in Animal Cells i. The cell membrane is drawn in until the cytoplasm is pinched into two equal parts. ii. Each part contains its own nucleus and organelles

Lesson Overview Cell Growth, Division, and Reproduction d. Cytokinesis in Plant Cells i. iii. In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall Instead, a cell plate forms between the divided nuclei that develops into cell membranes A cell wall then forms in between the two new membranes

Lesson Overview Cell Growth, Division, and Reproduction The Stages of the Cell Cycle

Lesson Overview Cell Growth, Division, and Reproduction Mystery Clue #2 How might the cell cycles of the cells surrounding the salamander’s wound be affected?

Lesson Overview Cell Growth, Division, and Reproduction Section 10. 3 REGULATING THE CELL CYCLE

Lesson Overview Cell Growth, Division, and Reproduction The 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.

Lesson Overview Cell Growth, Division, and Reproduction I. The Discovery of Cyclins a. Cyclins: a family of proteins that regulate the timing of the cell cycle in eukaryotic cells This graph shows how cyclin levels change throughout the cell cycle in fertilized clam eggs.

Lesson Overview Cell Growth, Division, and Reproduction II. Regulatory Proteins a. Internal regulators are proteins that respond to events inside a cell i. they allow the cell cycle to proceed only once certain processes have happened inside the cell b. External regulators are proteins that respond to events outside the cell i. they direct cells to speed up or slow down the cell cycle – Growth factors are external regulators that stimulate the growth and division of cells i. they are important during embryonic development and wound healing

Lesson Overview Cell Growth, Division, and Reproduction Mystery Fish #3 How might regulatory proteins be involved in wound healing in the salamander?

Lesson Overview Cell Growth, Division, and Reproduction III. Apoptosis a. Apoptosis is a process of programmed cell death b. Apoptosis plays a role in development by shaping the structure of tissues and organs in plants and animals c. For example, the foot of a mouse is shaped the way it is partly because the toes undergo apoptosis during tissue development

Lesson Overview Cell Growth, Division, and Reproduction IV. Cancer a. Cancer is a disorder in which body cells lose the ability to control cell growth b. Cancer cells divide uncontrollably to form a mass of cells called a tumor i. benign tumor is noncancerous, it does not spread to surrounding healthy tissue ii. malignant tumor is cancerous, it invades and destroys surrounding healthy tissue and can spread to other parts of the body iii. The spread of cancer cells is called metastasis iv. Cancer cells absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning

Lesson Overview Cell Growth, Division, and Reproduction V. What Causes Cancer? a. Cancers are caused by defects in genes that regulate cell growth and division b. Some sources of gene defects are smoking tobacco, radiation exposure, defective genes, and viral infection. c. A damaged or defective p 53 gene is common in cancer cells. It causes cells to lose the information needed to respond to growth signals.

Lesson Overview Cell Growth, Division, and Reproduction VI. Treatments for Cancer a. Some localized tumors can be removed by surgery b. Many tumors can be treated with targeted radiation c. Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

Lesson Overview Cell Growth, Division, and Reproduction Section 10. 4 CELL DIFFERENTIATION

Lesson Overview Cell Growth, Division, and Reproduction I. Defining Differentiation a. Differentiation: the process by which cells become specialized b. During development, cells differentiate into many different types and become specialized to perform certain tasks. c. Differentiated cells carry out the jobs that multicellular organisms need to stay alive.

Lesson Overview Cell Growth, Division, and Reproduction One of the most important questions in biology is how all of the specialized, differentiated cell types in the body are formed from just a single cell. d. Biologists say that such a cell is totipotent, literally able to do everything, to form all the tissues of the body. e. Only the fertilized egg and the cells produced by the first few cell divisions of embryonic development are truly totipotent.

Lesson Overview Cell Growth, Division, and Reproduction II. Human Development a. After about four days of development, a human embryo forms into a blastocyst, a hollow ball of cells with a cluster of cells inside known as the inner cell mass. b. The cells of the inner cell mass are said to be pluripotent, which means that they are capable of developing into many, but not all, of the body's cell types.

Lesson Overview Cell Growth, Division, and Reproduction III. Stem Cells a. Stem cells: unspecialized cells from which differentiated cells develop b. There are two types of stem cells: embryonic and adult stem cells.

Lesson Overview Cell Growth, Division, and Reproduction c. Embryonic Stem Cells i. Embryonic stem cells are found in the inner cells mass of the early embryo ii. Embryonic stem cells are pluripotent iii. Researchers have grown stem cells isolated from human embryos in culture iv. Their experiments confirmed that embryonic stem cells have the capacity to produce most cell types in the human body

Lesson Overview Cell Growth, Division, and Reproduction d. Adult Stem Cells i. Adult organisms contain some types of stem cells ii. Adult stem cells are multipotent iii. They can produce many types of differentiated cells iv. Adult stem cells of a given organ or tissue typically produce only the types of cells that are unique to that tissue

Lesson Overview Cell Growth, Division, and Reproduction IV. Potential Benefits a. Stem cell research may lead to new ways to repair the cellular damage that results from heart attack, stroke, and spinal cord injuries. One example is the approach to reversing heart attack damage illustrated below.

Lesson Overview Cell Growth, Division, and Reproduction V. Ethical Issues a. Most techniques for harvesting, or gathering, embryonic stem cells cause destruction of the embryo. b. Government funding of embryonic stem cell research is an important political issue. c. Groups seeking to protect embryos oppose such research as unethical. d. Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.

Lesson Overview Cell Growth, Division, and Reproduction Mystery Clue #4 Some adult salamander cells never completely differentiate. What ability do these cells retain?