Chapter Five: Cell Growth and Division

Section One: The Cell Cycle Cell Cycle: the regular patter of growth, DNA duplication, and cell division that occurs in eukaryotic cells. 4 Main Stages Gap 1 (G1) Synthesis (S) Gap 2 (G2) Mitosis (M)

Section One: The Cell Cycle Gap 1 (G1) Cell carry out normal functions but increase in size Organelle number increases Stage the cell stays in the longest Must pass a checkpoint before going into synthesis

Section One: The Cell Cycle Synthesis (S) The cell makes a copy of its DNA Cell contains two complete sets of DNA

Section One: The Cell Cycle Gap 2 (G2) Cells carry out their normal functions and continue to grow Checkpoint before Mitosis

Section One: Cell Cycle Mitosis (M) Includes mitosis and cytokinesis Mitosis: the division of the cell nucleus and its contents Nuclear membrane dissolves, duplicated DNA condenses around proteins and separates, and two new nuclei form Cytokinesis: the process that divides the cell cytoplasm resulting into two daughter cells that are gentically identical to the original cell

Section One: The Cell Cycle Rates of cell division vary based on cell type, the needs for that cell, and age Cell that divide rarely are said to be in the G0 stage Cell size is limited

Section Two: Mitosis and Cytokinesis Chromosomes One long continuous thread of DNA that consists of numerous genes along with regulatory information Human body has 46 chromosomes Must condense itself before mitosis can begin Allows them to divide evenly during mitosis DNA is loosely organized during interphase to allow easy access to genes so proteins can be made

Section Two: Mitosis and Cytokinesis Chromosomes At almost all times during the cell cycle your chromosomes are wrapped around histones Histones: a protein the organizes chromosomes around which they are wrapped Looks like beads on a string Helps to compact DNA Chromatin: the loose combo of DNA and proteins

Section Two: Mitosis and Cytokinesis Chromosomes Futher condensing occurs as mitosis gets closer and closer Chromatid: one half of a duplicated chromosome Each chromosome was copied during the S stage Together the two chromatids are called sister chromatids They are held together at the centromere Telomeres: the ends of DNA molecules that is made of repeating nucleotides that do not form genes

Section Two : Mitosis and Cytokinesis Interphase and Mitosis Interphase Duplication of organelles and DNA replication One cell should have two full sets of DNA and be large enough to divide Mitosis Prophase Metaphase Anaphase Telophase

Section Two: Mitosis and Cytokinesis Prophase Chromatin condenses into chromosomes Nuclear envelope breaks down Centrioles move to opposite sides (poles) of the cell Spindle fibers form

Section Two: Mitosis and Cytokinesis Metaphase Spindle fibers attach to each chromosome They align the chromosomes along the center of the cell

Section Two: Mitosis and Cytokinesis Anaphase Sister chromatids separate and go to opposite ends of the cell Spindle fibers shorten pulling the sister chromatids apart

Section Two: Mitosis and Cytokinesis Telophase Nuclear membranes start to form Chromosomes begin to uncoil Spindle fibers fall apart

Section Two: Mitosis and Cytokinesis Cytokinesis: divides the cytoplasm into two cells and completes the full stage of the cell cycle Animal cells: membrane forms a furrow that is pulled inward by tiny filaments like a drawstring Plant cells: a cell plate forms between the two nuclei

Section Three: Regulation of the Cell Cycle Cell Cycle Regulation Regulated by internal and external factors External Factors Cell to cell contact Growth factors: group of proteins that stimulate cell division Hormones Internal Factors Kinases and Cyclins Kinases transfer phosphate groups from one molecule to another and are activated by cyclins

Section Three: Regulation of the Cell Cycle Cell Cycle Regulation Apoptosis: programmed cell death Internal and external signals activate genes that produce self destructive enzymes Ex. Webbing of fingers and toes

Section Three: Regulation of the Cell Cycle Cancer Uncontrolled cell division Arises when regulation of the cell cycle breaks down Treated with chemotherapy or radiation Tumors form Benign tumors: cancer cells stay clustered together and are usually harmless Malignant tumors: cancer cell break away, or metastasize, from the tumor and spread to other parts of the body.\ Carcinogens Substances known to produce or promote cancer Tobacco smoke and air pollutants Some are carried by viruses

Section Four: Asexual Reproduction The creation of offspring from a single parent and does not involve joining sex cells The offspring are usually genetically identical to the parent Binary Fission: type of asexual reproduction by dividing into two roughly equal parts

Section Four: Asexual Reproduction Advantages Usually more efficient if the environment remains favorable Less time and energy Disadvantages No genetic variation

Section Four: Asexual Reproduction Some organisms reproduce asexually through mitosis Ex. Cutting a stem off a plant and repotting it Can go through budding, fragmentation, or vegetative reproduction

Section Five: Multicellular Life Multicellular Organisms Levels of Organization Cell Tissues: groups of cells that work together to perform a similar function Organs: groups of tissues that work together to perform a similar function Organ systems: groups of organs that carry out similar functions Work to maintain homeostasis

Section Five: Multicellular Life Cell Specialization Cell differentiation: the process by which unspecialized cells develop into their mature forms and functions Stem Cells: a unique type of body cell that has the ability to divide and renew themselves for a long period of time, remain undifferentiated in form, and develop into a variety of specialized cell types.

Section Five: Multicellular Life Stem Cell Types Adult In the brain, liver, bone marrow, skeletal muscle, dental pulp, and fat Also found in children and umbilical cord blood Can be taken out of a patient and put back in Embryonic Come from donated embryos grown in a clinic Can form any cell type in the human body