8-2 Cell Growth & Reproduction Biology Mrs 8-2 Cell Growth & Reproduction Biology Mrs. Geist Swansboro High School Fall 2010-2011 Photo Credit: © CAMR/A.B. Dowsett/Science Photo Library/Photo Researchers, Inc. Copyright Pearson Prentice Hall

Cell Size Limitations The larger a cell becomes, the more demands the cell places on its DNA. Larger cells have more trouble moving enough nutrients and wastes across the cell membrane. Ratio of Surface Area to Volume  (SA:V ratio) As the length of a cell increases, its volume increases faster than the surface area. As a cell grows, this SA:V ratio gets smaller. When the cell divides, the SA:V ratio increases.

Limits to Cell Growth As the length of a cell increases, its volume increases faster than its surface area. The resulting decrease in the cell’s ratio of surface area to volume makes it more difficult for the cell to move needed materials in and waste products out. Copyright Pearson Prentice Hall

Cell Reproduction Before it becomes too large, a growing cell divides forming two “daughter” cells. Before a cell divides, the cell replicates, or copies, all of its DNA. Each daughter cell gets one complete set of genetic information. Copyright Pearson Prentice Hall

8-2 Rapid Review As a cell increases in size, which of the following increases most rapidly? surface area volume Copyright Pearson Prentice Hall

8-2 Rapid Review If an imaginary cube-shaped cell has a length of 6 cm, its ratio of surface area to volume is 1 : 1. 6 : 1. 36 : 1. 1 : 6. Copyright Pearson Prentice Hall

8-2 Rapid Review The process by which a cell divides into two new daughter cells is called cell growth. cell division. DNA replication. cell multiplication. Copyright Pearson Prentice Hall

8-2 Rapid Review When one cell divides in two, what happens to the surface area to volume ratios in the new cells? There is no change in the amount of material exchanged. Each new cell can exchange more material than the original cell. Each new cell can exchange less material than the original cell. The two new cells cannot be compared to the original cell. Copyright Pearson Prentice Hall

8-2 Rapid Review When a growing cell undergoes cell division, each new cell gets half the DNA from the original cell. twice as much DNA as the original cell. a random sample of the DNA in the original cell. a full copy of all the DNA in the original cell. Copyright Pearson Prentice Hall

The Cell Cycle 2 Stages of Cell Division in eukaryotes: Mitosis: division of the cell nucleus. Cytokinesis: division of the cell cytoplasm Genetic information is passed from one generation to the next on chromosomes. Dark-staining structures that contain DNA and protein. Chroma- Greek for “colored” Soma- Greek for “body” Before cell division, each chromosome is duplicated, or copied.

Chromosomes Each chromosome consists of two identical “sister” chromatids. Centromere- holds sister chromatids together When the cell divides, the chromatids separate. Each new cell gets one chromatid. Sister chromatids Centromere Copyright Pearson Prentice Hall

The Cell Cycle Cell cycle- sequence of growth and division of a cell. Interphase is the period of growth that occurs between cell divisions. 3 stages: G1 S G2 During the cell cycle: a cell grows prepares for division divides to form two daughter cells

4 Phases of the Cell Cycle G1 (First Gap Phase) Cell grows synthesizes new proteins and organelles S Phase chromosomes are replicated DNA synthesis takes place G2 (Second Gap Phase) Organelles (ie. Mitochondria, chloroplast) and molecules required for cell division are produced Mitosis Copyright Pearson Prentice Hall

Cell Cycle During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases. Copyright Pearson Prentice Hall

4 Phases of Mitosis Prophase Metaphase Anaphase Telophase Copyright Pearson Prentice Hall

Mitosis Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells. Copyright Pearson Prentice Hall

Prophase Centriole Spindle forming The centrioles separate and move to opposite sides of the nucleus. A spindle begins to form Microtubules that help separate the chromosomes. Chromatin condenses to form visible chromosomes. The nuclear envelope breaks down. Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

Metaphase The second phase of mitosis Equator (imaginary midline) Metaphase Centromere Centriole The second phase of mitosis The chromosomes line up across the center (equator)of the cell. Microtubules connect the centromere of each chromosome to the poles of the spindle. Spindle Copyright Pearson Prentice Hall

Anaphase the third phase of mitosis. Individual chromosomes the third phase of mitosis. The sister chromatids separate into individual chromosomes. The chromosomes move toward opposite poles. Copyright Pearson Prentice Hall

Telophase the fourth and final phase of mitosis. Chromosomes gather at opposite ends of the cell and lose their distinct shape. A new nuclear envelope forms around each cluster of chromosomes. Copyright Pearson Prentice Hall

Cytokinesis the cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes. Copyright Pearson Prentice Hall

Cytokinesis Cell wall In plants, the cell plate forms at the equator. The cell plate develops into a cell membrane. A cell wall then begins to appear in the cell plate. Cell plate Cell wall Copyright Pearson Prentice Hall

8-2 Rapid Review The series of events that cells go through as they grow and divide is called the cell cycle. mitosis. interphase. cytokinesis. Copyright Pearson Prentice Hall

8-2 Rapid Review The phase of mitosis during which the chromosomes line up across the center of the cell is prophase. metaphase. anaphase. telophase. Copyright Pearson Prentice Hall

8-2 Rapid Review Cytokinesis usually occurs at the same time as telophase. after telophase. during interphase. during anaphase. Copyright Pearson Prentice Hall

8-2 Rapid Review DNA replication takes place during the S phase of the cell cycle. G1 phase of the cell cycle. G2 phase of the cell cycle. M phase of the cell cycle. Copyright Pearson Prentice Hall

8-2 Rapid Review During mitosis, “sister” chromatids separate from one another during telophase. interphase. anaphase. metaphase. Copyright Pearson Prentice Hall